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Accessory Apartment
A small apartment or studio located in house built with the intention of being rented to provide income for the support of the mortgage.

ACQ (Alkaline Copper Quanternary) Treated Wood
ACQ is a non-arsenic wood preservative, which is generally preferable to the common alternative CCA (Chromated copper arsenate). ACQ, however, is not completely environmentally benign. Like CCA, it can still leach copper which into water, harming aquatic organisms. ACQ wood is wood or lumber treated with ACQ as a preservative. (information from Environmental Building News v.13:10)

Advanced Framing (2x6) (OVE Framing)
The 2x6 advanced framing wall system is an adaptation of standard frame construction to reduce cost and material consumption while improving the wall's R-value. Standard 2x6 frame construction uses studs spaced at 16" on center. Advanced framing increases this spacing to 24" on center, in addition to using open corner framing, single top and bottom plates, and strategies to reduce the size and number of headers for bearing and non-bearing partitions. Advanced framing can also be combined with a modular layout to further reduce cost and material consumption.

There are several advantages to using advanced framing. First, it reduces the amount of studs and lumber required. This reduces both material and labor costs, resulting in a significantly cheaper wall. Second, lumber savings result in less material resource impacts, including less logging and reduced embodied energy in the wall. Third, wider stud spacing increases the amount of insulation in the wall, reducing thermal bridges and improving the R-value and energy performance of the wall. Advanced framing is particularly important when used with expensive insulation such as spray polyurethane foam. In this case, advanced framing helps maintain the high R-value of the insulation by reducing thermal bridging, and preserves the added financial investment in high performance insulation.

Advanced framing does have several drawbacks. It does not address air leakage, which is a large concern for both home energy performance and the long-term durability of the wall. Advanced framing may also require extra training for those unfamiliar with the system. This could entail extra cost and time until contractors learn the system. Some types of cladding are not designed for use with 24" on center attachment points.

For more information see: PATH Technologies, "Advanced Framing Technologies: Optimum Value Engineering (OVE)" Toolbase Services, www.pathnet.org.

Aerators are devices that screw into the nozzle of a faucet and mix air and water streams. Even with an older faucet, it is possible to purchase low-flow aerators that will reduce consumption at a very low cost. In addition to reducing water consumption, aerators can also help limit splashing and increase water velocity, making for a more effective rinse.

Aerobic Treatment System
Unlike standard septic tanks (anaerobic systems), aerobic treatment systems inject air into wastewater in order to improve the quality of outgoing water through the digestive action of aerobic bacteria. This may permit a smaller drain field than would be permitted with a standard septic tank. In an aerobic treatment system, wastewater is first flows through a pre-treatment area that allows large solids to settle out. Later the wastewater is aerated while bacteria digest, process, and clean the wastewater before it is released to the drainfield. (Toolbase Services, www.toolbase.org/index.aspx)

Composite panel products derived from recovered agricultural waste fiber from sources including but not limited to cereal straw, sugarcane bagasse, sunflower husk, walnut shells, coconut husks and agricultural prunings. The raw fibers are processed and mixed with resins to produce panel products with characteristics similar to those derived from wood fiber. (from Environmentally Preferable Products Database, www.eppbuildingproducts.org)

Air Barrier
An air barrier is any material or assembly of materials that stops the flow of air. To stop the flow of air, an air barrier must be free of holes and punctures. Otherwise, a pressure differential will drive significant quantities of air (and potentially water vapor) through the hole in a short period of time. Therefore, particular attention must be paid to preserving the continuity of an air barrier by reducing or eliminating even small punctures.

An air barrier should not be confused with a vapor retarder, which is a material or assembly designed to reduce water vapor diffusion. Since water vapor can move through a wall or roof by both diffusion and air movement, it is important to control both with the installation of an air barrier and a vapor retarder. However, it is important to note that air flow transports many times more water vapor than diffusion. Therefore, preserving the continuity of the air barrier is significantly more important in reducing the flow of water vapor through exterior walls and roofs than the presence of a vapor retarder. Confusion regarding vapor retarders and air barriers exists because the two are sometimes combined in one material. A common example is 6 mil polyethylene sheeting, which is used with varying effectiveness in stud-frame construction as both the air barrier and vapor retarder. Alternatively, a building house wrap such as Tyvek is permeable to water vapor but not air flow, allowing exterior walls to dry out through diffusion but not by air movement. The house wrap therefore acts as an air barrier, not a vapor retarder.

Air Sealing
Air sealing is the process by which air infiltration—air uncontrollably leaking into the house through cracks and openings—is prevented. Air sealing reduces heating and cooling costs, improves building durability, and creates a healthier indoor environment. (adapted from A Consumer's Guide to Energy Efficiency and Renewable Energy. U.S. Department of Energy, Energy Efficiency and Renewable Energy (EERE) office. www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic=11230.

Introduced in the 1940s, aluminum siding once enjoyed a fair share of the non-wood siding market. Soon after introduction it was offered in a variety of enameled colors. It was low maintenance, resistant to corrosion or deterioration, lightweight, durable, and needed minimal repainting. Aluminum siding's popularity declined after the introduction of vinyl siding, which is cheaper and unlike aluminum siding is not prone to do denting. Today, some aluminum and steel sidings have a PVC color protective coating which improves durability, offers greater color selection. These coatings increase the negative environmental impacts of the material by introducing PVCs into the product, and may affect recycling of the siding at the end of life.

Anaerobic Digester
The primary benefits of anaerobic digestion are nutrient, recycling, waste treatment, and odor control. Anaerobic digestion also produces biogas, a combination of methane and carbon dioxide from organic waste. The methane can be captured for energy production, an alternative to using gas or coal (which produce greater quantities of greenhouse gases and other pollutants) as an energy source. Anaerobically digesting food waste and yard scraps prevents these materials from being sent to landfills and reduces the production of harmful leachate there. The other byproduct of anaerobic digesters is acidogenic digestate, which is similar to compost. It is a valuable soil amendment that can improve plant growth, reduce soil erosion and nutrient run-off, alleviate soil compaction, and help soil retain water. It can also reduce the need for chemical fertilizers, and the resultant biogas from anaerobic digestions can be harvested over a matter of weeks as opposed to decades. (adapted from U.S. EPA, www.epa.gov/region09/waste/organics/ad/benefits.html and U.S. Dept of Energy, EERE, www.eere.energy.gov)

Annualized Fuel Utilization Efficiency (AFUE)
The AFUE is the measure of efficiency for furnaces on a 0 to 100 scale with 100 being the best performance possible. A point on the scale equals 1% of efficiency; therefore an 80 AFUE furnace is 80% efficient. A 78 AFUE is the government minimum and 97 AFUE is the current high rating.

Apparent Sensible Effectiveness (ASEF)
For an HRV or ERV, the measured temperature rise of the supply air stream divided by the difference between the supply temperature (point 1) and exhaust temperature (point 3) and multiplied by the ratio of mass flow rate of the supply divided by the minimum of the mass flow rate of the supply or exhaust streams. This value is useful principally to predict final delivered air temperature at a given flow rate.

Aquifers are porous soil or rock levels that yield significant amounts of water. Ground water is an important resource in our environment. It replenishes our streams, rivers, habitats and also provides fresh water for irrigation, industry, and communities. For many Americans, ground water is also the primary source of drinking water. However, ground water is highly susceptible to contamination from septic tanks, agricultural runoff, highway de-icing, landfills, and pipe leaks. (from U.S. EPA: www.epa.gov/ebtpages/watergroundwater.html)

Architecture 2030 Targets
These targets have been established by Architecture 2030, an non-profit organization created in response to the ever-increasing threats of climate change, with the intention to "transform the US and global Building sector from the major contributor of greenhouse gas emissions to a central part of the solution to the global-warming crisis." The immediate target of the 2030 Challenge is for "all new buildings, developments, and major renovations to meet a fossil fuel, GHG-emitting, energy consumption performance standard of 50% of the regional (or country) average for that building type." The 2030 Challenge requires that this target changes to achieve carbon-neutral building by 2030. The fossil fuel reduction standard increased to:

60% in 2010
70% in 2015
80% in 2020
90% in 2025
and carbon neutral by 2030.

(adapted from www.architecture2030.org)

Asphalt-impregnated Fiberboard
Asphalt-impregnated fiberboard is a light-weight sheathing product made from wood waste that can be used to provide a wall surface and shear strength for frame structures. Fiberboard is made from relatively low density wood fibers pressed together with resins. Because it is a low density product, it does not have the strength for foot traffic and cannot be used for roofs. Commonly, fiberboard is made with significant quantities of recycled post-consumer and post-industrial wood waste. Typically, exterior grade fiberboard is also coated in fire-retardants and asphalt to help resist water penetration. Exterior fiberboard is more vapor permeable than OSB and plywood, allowing water vapor to pass through without becoming trapped in the wall assembly. Fiberboard is also rated at R-2, providing improved insulation value compared to typical sheathing such as OSB and plywood.

Asphalt Shingles
Asphalt shingles are inexpensive, come in a variety of colors and shapes, and typically carry warranties of 20 or 30 years. There are two varieties of asphalt shingles: organic shingles and fiberglass shingles.

Organic shingles have a cellulose-fiber mat that is saturated with asphalt and then coated with mineral granules. They typically have a lower fire resistance rating than fiberglass shingles.

Fiberglass shingles have a fiberglass mat that is sealed on both sides by layers of asphalt, and coated with mineral granules.

Asphalt shingles are the most widely used roofing material in the United States—nearly two thirds of all roofs are clad in asphalt shingles*. As a result of the widespread use of asphalt shingles, roughly 11 million tons of asphalt roofing ends up in landfills annually. Efforts to recycle this material for use in road construction have been slowed due to slow approvals for use of asphalt shingles in hot mix asphalt by local, state, and federal departments of transportation. Currently, Mn/DOT allows for the use of up to 5% manufacturers' shingle scrap in hot-mix asphalt. (Environmental Building News, June 2000)

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A backdraft is reverse flow of air down a chimney or exhaust pipe caused by a low pressure in or around the combustion chamber. A backdraft can cause the build up of exhaust fumes, such as carbon monoxide and carbon dioxide, in the home. Carbon monoxide poising in low concentrations can cause headaches and in high concentration death.

A basement is the most common foundation in Minnesota's cold weather climate. Since foundation walls must extend 3.5 to 5.0 feet below grade, the addition few feet of wall and a concrete slab can provide an entire level of usable space. This additional space is usually regarded as a worthwhile trade-off for the additional cost. Basement walls can be concrete, concrete block, or wood. Walls must incorporate thermal and moisture control. Chronic moisture and potential health problems from mold in basements require reliable drainage and waterproofing systems that may increase costs above conventional practice. A typical windowless basement is suitable for mechanical equipment, laundry, and storage. Often living spaces and bedrooms are placed in basements as well. If there is an intention to use a basement for living space, the design must address indoor air quality, moisture control, daylighting, ventilation, and egress.

Bioaccumulation is the process by which the concentration of toxins tends to magnify as it moves up the food chain. For example, relatively low concentrations of toxins like mercury in water bodies can be found in the greatest concentrations of predatory fish, many of which humans eat.

Biodiversity is the diversity or variety of plant and animal species living in an area.

Biological Waste Treatment
A biological waste treatment system treats blackwater onsite using microorganisms and plants to clean and filter water.

Blackwater is wastewater that includes fecal matter. It requires more thorough cleaning and filtration than greywater.

Blower door test
A test performed on a house to determine its air tightness. The house is pressurized using a blower door, actually an insert that fits into a door opening with a blower and pressure gauges, the rate of air pressure loss is used to determine the leak rate and the air tightness of the structure.

Borax is a naturally occurring salt with a number of household and construction applications. It can be used as a cleaner, a fire retardant (often in batt or loose-fill cellulose and fiberglass insulation), an insecticide, and an anti-fungal additive (for treating wood). Because borate is water soluble, borate-treated wood has limited applicability in areas susceptible to moisture.

A brick is a hand sized rectangular building unit, roughly 2 ¼ x 3 ¾ x 8 inches, made from clay and hardened by heat, usually at high temperatures in a kiln/oven. Brick has been used for millennia as a building material. Bricks can be used as a load-bearing wall in residential construction, but this type of construction is rare today due to the labor cost and energy codes. More commonly, brick is applied as a veneer over other wall assemblies. Since brick is a relatively expensive cladding option for residential construction, it is often used in a decorative manner (as a wainscoting or only on the front facade of a house). Brick is very durable and requires little maintenance.

Brownfields are real property, the expansion, redevelopment, or reuse of which may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant. Cleaning up and reinvesting in these properties takes development pressures off of undeveloped, open land, and both improves and protects the environment. Brownfields should be redeveloped in concordance with the EPA's Brownfield Redevelopment Requirements. (U.S. EPA, www.epa.gov/swerosps/bf/)

Building Related Illness (BRI)
Building Related Ilnesses refer to symptoms that a person develops due to time spent in a building; these symptoms disappear when the person leaves the building. If these symptoms can be traced to a particular cause within the building, it is considered a building related illness. This is different from sick building syndrome, where a specific cause for the symptoms cannot be identified.

BTU stands for British Thermal Unit, a unit of measure for energy. A BTU is equal to the amount of heat energy required to raise the temperature of one pound of water by one degree Farenheit. One watt is equivalent to about 3.41 BTUs.

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Carbon Monoxide
Carbon Monoxide is a colorless, nearly odorless, and tasteless gas. It results from the incomplete oxidation of carbon in combustion. It can accumulate indoors from improperly vented or unsealed combustion appliances or equipment. At low concentrations, carbon monoxide may cause fatigue in healthy people or chest pain in those with heart disease. At higher concentrations, it causes impaired vision and coordination, headaches, dizziness, confusion, and nausea. At very high concentrations carbon monoxide gas is fatal. Carbon monoxide concentrations can be minimized in the home by keeping gas appliances properly adjusted, installing and using exhaust fans for gas stoves, opening flues when using fireplaces or wood stoves, keeping heating system in good repair, and isolating the garage from the living space. Jump to the Carbon Monoxide Detector page for more information. (U.S. EPA, www.epa.gov/iaq/co.html)

Natural carpets made from wool, grasses, or cotton reduce impacts compared to petroleum-based products. Off-gas emissions are generally less harmful, and natural carpets require less toxic chemicals to clean and maintain. In addition, natural carpets are biodegradable at the end of their service life. Carpets made from Nylon 6 or 6.6 fibers are very durable and can be recycled (either laterally or down-cycled), prolonging their life and keeping waste out of landfills. Carpets made from recycled PET derived primarily from post-consumer plastic soft drink containers reduce the amount of virgin material required, but have a higher embodied energy. This is due to recycling-related shipping and the recycling process itself. The primary benefit of recycled PET carpet is keeping waste material out of landfills. Carpet pads are either made from recycled carpet pad or recycled carpet fibers and help reduce the amount of material sent to landfills.

CCA (Chromated copper arsenate)
CCA is a wood preservative and pesticide. Wood treated with CCA is readily identified by its green color. The wood industry has voluntarily withdrawn the use of CCA for residential use.

Ceramic tile
Recycled-content tile can be made using waste glass from light bulbs, bottles, auto windshields, and byproducts from feldspar mining. At the end of its life cycle, tile can be ground up and used for base or fill. Choice of aesthetically flexible patterns and colors prolongs the life cycle of products. Appropriate installation methods ensure a longer life cycle. Tile's durability can reduce the environmental impacts associated with maintenance. Use low-VOC additives, mortars, grouts, and sealers.

Certified Wood
Certified wood comes from a forest managed according to the higher environmental standards set by a second or third-party forest certification organization. Many certification organizations exist including the Forest Stewardship Council (FSC), the Sustainable Forestry Initiative (SFI), and the Program for the Endorsement of Forest Certification (PEFC). These organizations develop forest management standards which must be followed and verified for each certified forest. Wood logged from these forests is marked "certified" and tracked through a chain of custody to it's eventual sale and use. Generally, management standards include setting a sustainable yield harvest, taking greater care to reduce environmental impacts during logging, preserving ecological diversity, minimizing "plantation"-style management, and implementing social guidelines to help local indigenous groups preserve their rights to forest access and control. Forest certification organizations rarely adopt the same level of environmental standards. Some certifications are less environmentally stringent than others.

CFC (chlorofluorocarbon)
CFCs can refer to any of a number of organic compounds made of carbon, fluorine, chlorine, and hydrogen. Since the mid-twentieth century they have been used as aerosol propellants, refrigerants, solvents, and foam-blowing agents (for instance, in insulation). CFCs accumulate in the stratosphere where they destroy ozone molecules.

A cistern is a large tank or reservoirs for storing rainwater.

A charrette is an intense workshop or meeting focusing on a project. It is a French word meaning small cart of wagon. Its use as noted here is attributed to the use of carts to collect student design work at the L'Ecole des Beaux-Arts where students would "charrette" or draw quickly as they followed the carts finishing drawings as they went.

Clay and Concrete Roofing Tiles
Clay roofing tiles traditionally were hand-made made using local sources of clay. Using local resources and traditional skilled labor is valuable as it reduces transportation energy use and supports local economies. Although progress has been made to increase energy efficiency, the clay-firing process is still energy-intensive, resulting in a very high embodied energy and global warming potential. Concrete was introduced more recently as a cheaper alternative to clay with similar properties and aesthetics. Since concrete tiles do not need to be kiln-dried, the embodied energy and global warming potential of concrete tiles is significantly less. However, preparing cement is still an energy-intensive process and as the concrete cures, chemical reactions between the water, cement, and aggregate release large amounts of carbon dioxide. As a result, concrete tiles are still a relatively high-embodied energy product with high global warming potential. The long-lifespan of concrete and clay tiles (typical warranties of 50 years or more) somewhat reduces the high environmental impact of the tiles, but should be matched to a building with a similarly long life span. In cold climates with frequent freeze/thaw cycles, special care must be taken during roof design and installation to ensure long life.

The broader grouping of liquid substances applied for protection or decoration, including paints, varnishes, stains, and lacquers. All these products are generally made from pigments, thinners, resins and additives used to enhance specific characteristics.

Coefficient of Performance (COP)
COP is the measure of heating efficiency for a ground source heat pump, or the measure of heating efficiency for an air-source heat pump at a specified ambient air temperature. Units with higher COPs have greater efficiency. COP is calculated by dividing the amount of heat energy produced (in BTU) by the amount of energy consumed (in BTU equivalent). Ground-source heat pumps commonly range between 3.0 and 4.5 at typical ground conditions in winter (32°F). This means they generate 3 to 4.5 times more heat than they consume.

In cogeneration, "waste" heat from the generation of electricity is captured and used as a heat or energy source.

Color Rendering
The ability of a light source to display the color of an object. Color rendering is often measured against daylight or "ideal" light.

Color Temperature
Color temperature refers to how the eye sees the color of light. Measured in Kelvins (K), a low the temperature reading indicates a warm color of light. Incandescent bulbs appear to have a yellowish hue, with a color temperature of around 2700 K. Fluorescents range from 3000 K (warm white) to 4000 K (cool white). For reference, daylight can range from 5000 to 10000 K. Colors of light have no direct association with the actual Kelvin temperature reading, rather it refers to the temperature required to heat a blackbody radiator to the color desired. (adapted from, Lindsay Audin, et al., Lighting Technology Atlas, vol.1, 1994).

Compost is a blend of aerobically decayed organic matter. It can be used as a soil additive, as fertilizer, for erosion control, or in wetland reconstruction. Compost is cultivated on many scales, from the backyard compost bin up to industrial composting operations that serve entire communities.

Composting Toilet
A composting toilet generates compost from human waste. In addition to retrieving nutrients that are otherwise lost to biological cycles, composting toilets generally do not require water for flushing and therefore dramatically reduce overall household water consumption. Advancements in the technology have eliminated the associated smells and a bulk of the labor required to keep a working system.

Composite/Synthetic (Rubber & Plastic) Shingles
Recently, manufacturers have started to produce shingles made largely from recycled rubber and plastic. They typically resemble slate or cedar shakes and offer an alternative to other high-end roofing materials. Their weight is comparable to a higher-grade asphalt shingle, and they are priced to compete with cedar shakes and shingles. They have warranties that range from 40-50 years, excellent resistance to hail and wind, and good sound insulation properties.

Concrete Block
Also known as a concrete masonry unit, or CMU, concrete blocks are modular pre-cast hollow concrete bricks which are used in construction, often with steel reinforcing.

Concrete Block Foundation
A concrete block basement foundation with installed reinforcement provides a stable, long-lasting construction with high fire resistance and the potential for good moisture control. However, concrete by itself is moisture permeable and a high quality waterproofing system is recommended (petroleum-based in most cases). In addition, exterior insulation is recommended to create an energy efficient assembly and reduce problems with moisture condensation on cold concrete surfaces. Concrete has an inherently large environmental impact, but is an extremely durable and long-lasting construction material, ideal for use below grade. Inclusion of waste products such as fly ash and blast furnace slag reduce the need for cement, and can thereby reduce CO2 emissions and related air and water pollution associated with concrete.

Concrete Masonry Unit (CMU)
Concrete masonry units are an efficient use of cement and provide a strong and durable structure. They have a high embodied energy because of the heat required to process them. They can be insulated and can provide a heat-sink component to interior design. They require waterproofing, some type of internal or external insulation, and, depending on the height of the building, may require additional reinforcement, such as rebar. The more materials required for the installation, the higher the environmental impact.

Condensing Furnace
A condensing furnace extracts additional heat from the exhaust by condensing water vapor in the exhaust gases. This reduces the amount of heat lost with the exhaust, increasing the furnace's efficiency. The water that is condensed must be drained to a floor drain. Efficiencies of 89 to 97 AFUE are possible.

Constructed Wetlands
A constructed wetland is man-made, marshy area used to improve the quality of wastewater and/or stormwater runoff. Like natural wetlands, they employ aquatic plants to remove pollutants and excess nutrients (like nitrogen and phosphorus) from water through natural filtration processes.

Cork comes from a renewable resource but must be shipped from Europe and North Africa, increasing embodied energy. Cork flooring requires minimal maintenance, produces minimal off-gassing, and is very durable if used appropriately. Select low-VOC adhesives, cleaners, and finish coatings.

Crawl Space
Crawl spaces are not a common foundation type in Minnesota. Crawl spaces are typically more expensive to construct per square foot of habitable area than other foundation types. They are also historically difficult to construct properly, and many crawl spaces are plagued by moisture condensation, mold, and deterioration issues. However, a crawl space achieves the appearance of a raised floor which can be important in some cases to achieve a certain house scale and height appropriate for the neighborhood context. Traditionally, crawl spaces were vented with outside air to remove moisture. This requires insulation in the crawl space ceiling to keep the floor of the house warm. It also means that pipes and ducts located in the crawl space are exposed to outside air. Research has shown that in most climates, vented crawl spaces are not effective in terms of energy use and moisture control. Therefore, an unvented crawl space is now recommended. An air-tight moisture barrier on the floor and exterior crawl space walls is essential. The walls may be poured concrete, concrete block, or wood, and should be insulated. The crawl space is then conditioned as a zone of the house. Another raised floor option which minimizes cost and material use is a low-cost pile foundation. Piles are placed at the appropriate depth and spacing and filled with concrete. The wood floor is then supported on steel beams connecting the grid work piles. However, a thermal perimeter skirt is required to maintain a conditioned crawl space.

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Daylighting is the use of daylight to provide illumination for interior spaces, thus reducing the dependence on electric light.

A unit used to measure the relative loudness of sounds. One decibel is roughly equal to the difference in loudness ordinarily detectable by the human ear. Decibels are arranged on a logarithmic scale, starting at 1 decibel, which is the faintest sound normally audible, and doubling in volume (or loudness) every 10 decibels. The theoretical maximum intensity of sound in earth's atmosphere is 194 dB.

Demand (Tankless) Hot Water Heater
A demand tankless hot water system only heats water when the tap is turned on and can be powered by electricity or natural gas. The system eliminates the energy requirements of maintaining a tank of water at high temperature. Tankless systems are best installed with as short a pipe run as possible to the tap

A desuperheater takes excess heat from the home during the cooling season and transfers it (through a heat exchanger) to the hot water supply. This is an optional component of a heat pump system.

Direct Vent
A fireplace, furnace, water heater which vents exhaust gases directly to the exterior.

Direct Vent Fireplace
A direct vent gas fireplace is one that has a built-in fan leading to the exterior of the building to prevent backdrafting. Gas fireplaces are more efficient at retaining heat inside a building than traditional wood fireplaces that release most of their heat up the chimney.

Domestic Hot Water (DHW)
Domestic hot water refers to a households hot water supply. There is a wide range of production options, including, a conventional hot water heater, an on-demand tankless hot water heater, solar hot water, and ground coupled heat pumps.

Double Glazing
In general, any use of two layers of glass separated by an air space within an opening to improve insulation against heat transfer and/or sound transmission. In factory-made double glazing units, the air between the glass sheets is thoroughly dried and the space is sealed airtight, eliminating possible condensation and providing superior insulating properties. It also allows for between-glass shading options such as muntins, blinds, and pleated shades. (from Window Systems for High-Performance Buildings, John Carmody, et al.)

Drain Tiles
Drain tiles are perforated pipes placed near the footing of a foundation to facilitate water drainage. They have also been used by farmers to drain low lying areas of crop fields.

Drain Water Heat Recovery
80-90% of the energy used to heat water is carried away with it down the drain. Drain water heat recovery systems capture this energy to preheat cold water entering the water heater or going to other water fixtures. Drain water heat recovery technology works well with all types of water heaters, especially with demand and solar water heaters. Drain water heat exchangers can recover heat from hot water used in showers, bathtubs, sinks, dishwashers, and clothes washers. They generally have the ability to store recovered heat for later use. A unit with large storage capacity is needed for use with a dishwasher or clothes washer. Without storage capacity, there is only useful energy recovery during the simultaneous flow of cold water and heated drain water, like while showering.

Some storage type systems have tanks containing a reservoir of clean water. Drain water flows through a spiral tube at the bottom of the heat storage tank. This warms the tank water, which rises to the top. Water heater intake water is preheated by circulation through a coil at the top of the tank.

Non-storage systems usually have a copper heat exchanger that replaces a vertical section of a main waste drain. As warm water flows down the waste drain, incoming cold water flows through a spiral copper tube wrapped tightly around the copper section of the waste drain. This preheats the incoming cold water that goes to the water heater or a fixture, such as a shower.

Prices for drain water heat recovery systems range from $300 to $500 and need to be installed by qualified plumbing and heating contractors. Installation is usually less expensive in new construction. Paybacks range from 2.5 to 7 years, depending on how often the system is used. (from U.S. Department of Energy, EERE, www.eere.energy.gov/consumer/your_home/water_heating/index.cfm/mytopic=13040)

Drip Irrigation
A system of irrigation that supplies water in a slow, even amount through under ground or near surface pipes/tubes. Drip irrigation reduces water loss due to evaporation and the potential for soil erosion due to runoff.

Dry Bulb Temperature
The temperature of the air as measured by a standard thermometer. (from U.S. Department of Energy, EERE, www.eere.energy.gov)

Dual Flush Toilets
A dual flush toilet allows the user to select a small flush or large flush option depending on the need. This feature reduces the overall amount of water used for flushing.

Duct Leakage Test
A duct leakage test involves sealing all the supply and return vents in a HVAC system and then blowing a fan into the ducts in order to test the air pressure in the ducts. A loss in pressure will indicate leaks in the system that need repair. It is important to run a duct leakage test to increase the efficiency of the system, and prevent possible related IAQ issues.

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Ecological System (Ecosystem)
An ecological system is a natural system of interrelated and interdependent elements. A forest is an ecological system in which trees, birds, and animals share a joint habitat.

Embodied Energy
Embodied energy refers to the total amount of energy associated with the creation of a material or product up to its point of use, including energy consumed in raw material extraction, manufacture, transportation, and installation.

Energy Efficiency Ratio (EER)
EER is the measure of cooling efficiency for a ground source heat pump, or the measure of cooling efficiency for an air conditioner or air-source heat pump at a specified ambient air temperature. Units with higher EERs have greater efficiency. EER is calculated by dividing the heat removed per hour (in BTUs/hr) by the power drawn by the unit (in watts). Ground-source heat pumps commonly range between 14.0 and 19.0 at typical ground conditions in the summer. Cooling efficiency in EER can be converted to SEER for comparison with air conditioners and air-source heat pumps.

Energy Factor
An energy factor (EF) is the measure of efficiency for water heaters.

Energy Recovery Ventilator
An energy recovery ventilator is similar to a heat recovery ventilator; ); it is used to provide fresh ventilation air that is pre-warmed or pre-cooled with outgoing exhaust air. ERVs have the added ability to transfer moisture in addition to heat between incoming and outgoing air streams. The ability to transfer moisture out of humid, incoming air is important when the unit is used to provide ventilation in the summer. This is why ERVs are used more frequently in warm, humid climates.

ENERGY STAR is a program of the U.S. Environmental Protection Agency and the Department of Energy to encourage the development and purchase of energy efficient building components and appliances. Visit the ENERGY STAR web site www.energystar.gov.

Engineered lumber
Manufactured building materials and components made from wood or wood pulp used in building. Including sheathings such as plywood, and OSB panels, and structural elements such glulam beams, wood I-joist and wood trusses.

A lose of soil caused by wind and water. Jump to the Erosion Control page for more information on erosion mitigation.

Erosion Control Blankets
An erosion control blanket is used to stabilize loose or easily eroded soils until vegetation is established. It is can be made from natural and biodegradable products or synthetic materials.

Eutrophication is the process by which oxygen levels in water decrease, killing marine life. It is often caused by excessive nutrient run-off into natural waterways that prompts excessive plant and algae growth on the surface, blocking sunlight and reducing water oxygen levels.

Expandable Foam and Caulk
Sealant and caulks that expand, like shaving cream, and are used as air sealant and insulations for small wholes. Non-expandable foam is used around windows and doors to air seal gaps between the frame and the wall.

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Faucets, Bathrooom
The Energy Policy Act of 1992 requires bathroom faucets use 2.2 gpm or less. Bathroom faucets are available that use significantly less water than the required minimum. The EPA labels many faucets that use less than 1.5 gpm with the WaterSense label. The addition or replacement of a flow-restricting aerator can also significantly reduce water consumption without necessitating a complete faucet replacement.

Faucets, Kitchen
The Energy Policy Act of 1992 requires kitchen faucets use 2.2 gpm or less. Kitchen faucets are also available in low-flow models, but greatly reduced flows can make some kitchen tasks more time consuming and labor intensive. Aerators can further reduce the amount of water consumption.

Fiber-cement Board
Current fiber-cement products are direct descendants of asbestos-cement building products that were widely used until the 1970's, but contain no asbestos. Fiber-cement products are formed from a mixture of cement and wood fiber (which constitutes 8-10% of the material). Fiber-cement board products are typically 5/16" thick. Fiber cement plank and lap siding is available in a variety of widths and finish textures. Panels are available in 4' x 8', 9', or 10' sheets. Some fiber-cement panel manufacturers offer a stucco finish in addition to smooth or wood-grain textures. Several fiber-cement manufacturers now offer accessory trim, soffit, and fascia elements. Fiber cement materials can be worked with woodworking tools, and should be finished with an alkali-resistant paint, although some can be used unpainted if handled carefully to avoid scratching. Most fiber-cement products come with a 50-year manufacturer's warranty. Due to the relative newness of these products true longevity is unknown. It is expected that fiber-cement products will need less frequent repainting than wood products, since it expands and contracts less with fluctuations in moisture.

Fiber-cement: Shakes, shingles, panels
Fiber-cement composites are made from wood fiber, fine aggregate, and cement. Some manufacturers may use post-industrial autoclaved concrete and/or post-consumer newsprint. This produces a lighter weight, fireproof product with a life cycle term up to 60 years. These products can be ground into a reusable dust at the end of their useful life, although programs are not available everywhere and may result in the products ending up in landfills.

Flash and Seal
Flash and seal refers to the installation of flashing and sealants, such as caulks, to prevent moisture from entering structural cavities. It is part of the weatherization of a home or building.

A thin, continuous sheet of metal, plastic, rubber, or waterproof paper used to prevent the passage of water through a joint in a wall, roof, or chimney. (from Fundamentals of Building Construction, 4th ed. Edward Allen and Joseph Iano, 2004)

Land subject to flooding includes any land at an elevation lower than 5' above the 100-year flood line as defined by the Federal Emergency Management Agency (FEMA)

At room temperature, formaldehyde is a colorless, flammable gas that has a distinct, pungent smell. It is also known as methanol, methylene oxide, oxymethyline, methylaldehyde, and oxomethane. Formaldehyde is naturally produced in small amounts in our bodies. Formaldehyde can cause irritation of the skin, eyes, nose, and throat. High levels of exposure may cause some types of cancers. It is possible that people with asthma may be more sensitive to the effects of inhaled formaldehyde. It is used in the production of fertilizer, paper, plywood, and urea-formaldehyde resins. It is also used as a preservative in some foods and in many products used around the house, such as antiseptics, medicines, and cosmetics. Jump to the Formaldehyde page for more information. (from Department of Health and Human Services, www.atsdr.cdc.gov/tfacts111.html#bookmark02)

Formaldehyde-free Materials
Urea-formaldehyde is a volatile organic compound used in glues and resins in the manufacture of some wood products. Exposure to formaldehyde can have adverse impacts on the human respiratory system and may be an asthma trigger. Formaldehyde-free materials are materials that do not contain these compounds. For more information see www.epa.gov/iaq/formalde.html

Frost-Protected Shallow Foundation
A frost-protected shallow foundation (FPSF) is a type of slab-on-grade foundation that is not common in Minnesota, but is used more frequently in warmer areas of the United States. However, even in Minnesota, FPSF's can save time, material, and money on the construction of a foundation. Because they are well-insulated, FPSF's are also more energy efficient than typical slab-on-grade foundations. A FPSF does not extend to the full depth of frost penetration (typically 3 ½ to 5 feet in Minnesota). Rather, a FPSF uses a thickened edge slab or grade beam that typically extends only 1 foot below grade, along with placement of rigid vertical and horizontal "wing" insulation below grade. The horizontal insulation forms a protective "skirt" that prevents frost from penetrating below the grade beam. By extending only 1 foot below-grade, this foundation system minimizes excavation and concrete use, reducing costs and construction time. NAHB publishes a design guide which specifies the depth, thickness, and width of the insulation required for various climates. Since the insulation is placed below grade, it must be rated for wet conditions (typically XPS rigid insulation).

FSC (Forest Stewardship Council)
The Forest Stewardship Council is an international non-profit organization that sets standards for sustainable forestry practices. It licenses third party organizations to certify products that are made from forests managed in keeping with their standards.

Functional Equivalent
In the analysis of building products or building assemblies, an accurate comparison can only be made if the subjects being compared are functionally equivalent. For instance, comparing rigid XPS foam and fiberglass batt insulation on a cost per inch basis is not an accurate comparison. The two insulation products are not functionally equivalent since XPS insulation provides a higher R-value per inch of thickness than fiberglass batts. To make a comparison based on functional equivalence, it is necessary to compare the cost based on the price per R-value instead. Functional equivalence can be hard to determine when involving assemblies with multiple layers and products. For example, a comparison between a SIP wall and a stud wall with fiberglass batts and sheathing but no air or vapor barrier, would not be an accurate comparison because the walls are not functionally equivalent. The SIP wall incorporates an air and vapor barrier by the nature of its construction and materials, while the stud wall with fiberglass batt insulation does not. An additional layer of polyethylene sheeting must be attached to the stud wall before it can be considered to perform the same range of functions.

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Garden Basement
Traditionally, garden basements have not been common in Minnesota, but they are now growing rapidly in popularity, for a number of reasons. Since traditional foundation walls must extend 3 ½ to 5 feet below grade, a garden basement can take full advantage of this fact by providing living space partially below grade without increasing the amount of concrete or excavation required. The below grade portion of the walls can be concrete, concrete block, or wood. The above-grade portion of the basement wall can utilize the same wall system as the rest of the house. The living space provided in garden basements can be of higher quality than full-height basements because there is space for the installation of full-size windows, which are installed following conventional practice. In addition, the space is provided with a natural thermal advantage in both the summer and winter since it is partially buried by earth. However, the design and construction of a garden basement must still address all the issues associated with a "habitable basement" including indoor air quality, moisture control, daylighting, ventilation, and egress. For example, reliable drainage and waterproofing systems may increase costs but are essential.

Green Roof
A green roof consists of vegetation and soil, or a growing medium, planted over a waterproofing membrane. Additional layers, such as a root barrier and drainage and irrigation systems may also be included.

Green roofs can be used in many applications, including industrial facilities, residences, offices, and other commercial property. In Europe, they are widely used for their stormwater management and energy savings potential, as well as their aesthetic benefits. (from www.epa.gov/hiri/strategies/greenroofs.html)

Green Seal Standard
Green Seal in a independent non-profit organization that sets environmental standards for products and services. Standards are based on a life-cycle approach to considering a product's environmental attributes. Green Seal products have been scientifically tested to meet the organization's standards which are based on the Guiding Principles and Procedures for Type I Environmental Labeling adopted by the International Organization for Standardization. Products that Green Seal certifies include paints, windows, paper, and floor care products among others. (adapted from Green Seal, www.greenseal.org)

Greywater is any water that has been used in the home, except water from toilets. Dish, shower, sink and laundry water comprise 50-80% of residential "waste" water. Greywater systems collect and hold water for use in landscape irrigation and for flushing of toilets.

Ground Coupled Heat Pumps (Geothermal)
A ground coupled heat pump is a combined heating, cooling, and hot water system, and is also referred to as geothermal. Ground coupled heat pumps exploit the consistent temperature of the earth as a heat source and sink. A loop of liquid is connected to a compressor, which expels or absorbs heat depending on the season.

Gypsum Sheathing
Exterior gypsum sheathing is a fiberglass-faced gypsum sheathing board used as a substrate for exterior claddings. It has a noncombustible core, composed essentially of gypsum and is faced with a water-resistant layer of fiberglass on all sides. It is manufactured with either a square or a tongue-and-groove edge. A wide range of exterior grades are manufactured varying from water resistant to water repellent.

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The environment in which a plant or animal naturally grows or lives.

Hardboard siding products are produced from low-grade trees, which are turned into wood chips, fiberized, mixed with phenol formaldehyde (PF), paraffin, and alum, then compressed and baked at a high temperature. Hardboard products need to be painted to maintain moisture protection.

Hardwood Flooring
Wood flooring has a high aesthetic value for residences. It also has a long life cycle and is relatively easy to maintain over time. Most wood flooring is derived from hardwood trees, which can come from local/regional or certified sustainable forests. Reclaimed or salvaged wood flooring saves materials and can come from species, grain types, or sizes of trees no longer available. From an environmental standpoint, this approach saves materials from the waste stream while eliminating impacts on living trees. Use water-based and low-VOC floor coatings, finishes, and cleaners to further minimize environmental impacts.

Hydrochlorofluorocarbons are a group of ozone depleting chemical currently being phased out of use, with 100% phase out by 2030.

Heat Island
Suburban and urban areas are often 2 to 10°F warmer than nearby rural areas. Heat islands form as cities replace natural land cover with pavement, buildings, and other structures. Built areas absorb more of the sun's heat than do natural surfaces, causing surface and air temperatures to rise. The loss of trees and shrubs also eliminates the natural cooling effects of shading and evapotranspiration, a process that draws heat from the air to convert water contained in vegetation to water vapor. Heat islands can increase air conditioning demand, the incidence of heat-related illness and mortality, and power plant emissions of air pollution and greenhouse gases. In addition to this direct increase in power plant emissions, elevated ambient temperatures can speed up the heat-dependent reaction that forms ground-level ozone. Installing cool or green roofs and planting shade trees and vegetation in urban areas can mitigate heat islands. (from U.S. EPA, www.epa.gov/heatisland/resources/faq.html#1)

Heat pump
A heat pump is a device that moves heat from a source, concentrates it, then releases it to a desired location. A heat pump can both heat and cool indoor space depending on the direction it pumps heat. One use for this technology is with a geothermal system.

Heat Recovery Ventilator (HRV)
A heat recovery ventilator is a device used to provide controlled quantities of fresh ventilation air that is warmed with the heat from outgoing exhaust air. Heat recovery ventilators transfer heat between exhaust air and incoming fresh air with the use of a heat exchanger without mixing air streams. This process saves energy by capturing the heat from warm, stale air before it is exhausted to the outdoors.

HEPA (High Efficiency Particulate Air) filters
A High Efficiency Particulate Air or HEPA filter is typically a throwaway dry media filter which removes 99.97% of particulate matter from the air bigger then 0.3 micrometers in diameter.

A unit used to measure the frequency, or pitch, of sounds. Relative to human hearing, low pitch sounds are generally in the range of 12 to 150Hz, while high-pitch sounds on the edge of human perception range up to 20,000 Hz. Human speech ranges between 125-4000 Hz.

Albedo is the ability of a surface material to reflect incident solar (short wave) radiation. It is expressed on a scale of 0 to 1 where a value of 0.0 indicates that a surface absorbs all solar radiation, and an albedo value of 1.0 represents total reflectivity. Light-colored surfaces generally have higher-albedos than dark-colored surfaces. Because they reflect most solar radiation, high-albedo materials can reduce the heat island effect. (from U.S. EPA, www.epa.gov/heatisland/resources/faq.html#1)

Hot Water Heater (Conventional)
A conventional hot water heater is comprised of a tank that continuously maintains water at a set temperature and is typically powered by electricity or natural gas

A device that measures and regulates the amount of humidity in the indoor environment. Humidistats installed in bathrooms can automatically trigger an exhaust fan when the humidity in the room exceeds a set threshold.

Hydrological Cycle
The natural cycle of water between atmospheric water precipitating to groundwater and surface water and evaporating back to the atmosphere.

HVAC is the acronym of Heating, Ventilation, and Air Conditioning, and in homes generally refers to the furnace, fresh air supply, and air conditioner.

Hydroseeding is a process of seed dispersal that is often used to help prevent erosion and to encourage quick growth of the seed. Seed is combined with water, and sometimes mulch, so that it can be sprayed over large surfaces in a small amount of time.

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ICF (Insulated Concrete Form)
Even though this system relies on poured concrete, with its attendant high environmental impacts due to cement and aggregate use in concrete, using stay-in-place insulating formwork in foundation walls (ICF) improves overall environmental performance for basement construction. Use of these forms can reduce the amount of concrete needed and provides insulation value as well. There are impacts associated with the rigid insulation, but in a good construction, there will be insulation used at the foundations anyway, so it is not adding another material.

Impervious Surface
A surface—such as traditional asphalt pavement—that does not allow water to infiltrate into the ground. Large areas of impervious surfaces lead to increased polluted run-off.

Indoor Air Quality (IAQ)
Indoor Air Quality is the measure of pollutants in an indoor environment. A growing body of scientific evidence has indicated that the air within homes and other buildings can be more seriously polluted than the outdoor air in even the largest and most industrialized cities. Other research indicates that people spend approximately 90 percent of their time indoors. Thus, for many people, the risks to health may be greater due to exposure to air pollution indoors than outdoors. (from U.S. EPA, www.epa.gov/iaq/pubs/insidest.html#Intro) Jump to the IEQ section for more information.

Indoor Environmental Quality (IEQ)
Indoor environmental quality refers to the ability of a place to support and enhance human comfort and well-being. The factors involved are lighting, air quality, access to views, and thermal comfort.

Induced Draft Power Vented Equipment
A system that actively vents a furnace to prevent potential backdrafting of harmful flue gasses, like include carbon monoxide and carbon dioxide. These systems can be employed with furnaces and water heaters.

Infiltration Basin
An infiltration basin is typically used for stormwater detention after and during a major rain event. They are very effective at providing groundwater recharge while diverting stormwater from treatment facilities or major waterways. They are designed to have a combination of high percolation and evapotranspiration rates in order to mediate a storm within 72 hours of its occurrence.

The U.S. EPA does not recommend the use of infiltration basins in ultra-urban areas, watershed with risk of chronic oil spills or other contaminant spills, regions with cold winters and snowmelt/freeze and thaw conditions, regions with sole-source aquifers, and areas with predominantly clay or silt soils. Soils with a combined silt/clay percentage of over 40 percent by weight are susceptible to frost heave and are not good candidates for infiltration basin applications. Basins are also unsuitable if the site is located over fill soils that form an unstable upgrade and are prone to slope failure. Jump to the Bioretention page for more information. (from "Protecting Natural Wetlands: A Guide to Stormwater Best Management Practices." U.S. EPA. 1996. www.epa.gov/owow/wetlands/pdf/protecti.pdf)

Infiltration System
A system that collects and brings storm water runoff from impervious surfaces (e.g. roofs, paved surfaces) to a pervious area such as a raingarden where it is allowed to seep into the ground. Jump to the Bioretention page for more information.

The public works of a country, state, or region, including roads, electricity, water, gas, sewer, and storm water services.

Insulated Core Door
An exterior door with core of foam insulation improves the energy efficiency of the building envelope by increasing the R-value of the door and minimizing thermal bridging.

Insulated Concrete Form Foundation
A basement foundation constructed with insulated concrete forms is generally drier, healthier and more energy efficient than other basement foundation options. Although this wall assembly generates incrementally higher embodied energy and global warming impacts, the increased energy performance outweighs these drawbacks. Use of insulated concrete forms can reduce the amount of concrete needed and cuts down on construction waste since the forms are left in place.

Insulating Glass Unit (IGU)
A combination of two or more panes of glass with a hermetically sealed air space between the panes of glass, separated by a spacer. This space may or may not be filled with an inert gas, such as argon. (from Window Systems for High-Performance Buildings, John Carmody, et al.)

Integrated Pest Management
Integrated pest management is an ecological approach to pest management utilizing plants and animal species as a means of controlling invasive and unwanted species, rather then relying on chemical insecticides.

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Laminate Flooring
This type of flooring uses engineered wood products as a substrate, reducing use of prime wood; however, most laminates include petroleum-based resins and have high embodied energy due to the pressure-treatments required for laminations. They may off-gas formaldehyde and require some recoating to preserve their finish. Laminates are not recommended for high-traffic areas because they cannot be refinished more than once and must be landfilled or burned, causing additional pollution. When laying laminate flooring, use low-VOC adhesives or mechanically fasten. When finishing, use low-VOC cleaners and finishes.

Latent Heat
Latent heat is the heat energy that is absorbed or released as water changes phase between liquid, gas, or solid. It excludes sensible heat, which is the heat that causes a change in temperature. Total heat is calculated by adding sensible and latent heat.

Lead is a highly toxic metal that was used for many years in products found in and around our homes. Lead may cause a range of health effects, from behavioral problems and learning disabilities, to seizures and death. Children 6 years old and under are most at risk, because their bodies are growing quickly. Lead poisoning is a top environmental health hazard for young children, affecting as many as 1.7 million children age five and under, according to Centers for Disease Control and Prevention (CDC) data.

Research suggests that the primary sources of lead exposure for most children are:
      · Deteriorating lead-based paint,
      · Lead contaminated dust, and
      · Lead contaminated residential soil.

Although lead-based house paint has long since been taken off the market, children living in older homes are threatened by chipping or peeling lead paint, or excessive amounts of lead-contaminated dust. More than 80 percent of homes built before 1978 contain lead paint. Even at low levels, lead poisoning in children can cause IQ deficiencies, reading and learning disabilities, impaired hearing, reduced attention spans, hyperactivity and other behavior problems. Pregnant women poisoned by lead can transfer lead to a developing fetus, resulting in adverse developmental effects.

According to the CDC, children at greatest risk include: poor children, minority children, children who are exposed to lead-containing home remedies, cosmetics, and ceramicware, and children of occupationally exposed adults. Risk for these children is compounded by residing in older housing. If not conducted properly, certain types of renovations can release lead from paint and dust into the air. Federal law requires that contractors provide lead information to residents before renovating pre-1978 housing. The EPA and other organizations offer guidance for reducing lead hazards during the renovation or demolition of older buildings. (from U.S. EPA, www.epa.gov/lead/)

Life Cycle Impact
A material, product, or building's life cycle impact refers to its effects on the environment over the entire course of its existence (from raw material extraction, manufacture, transportation, installation, operation and use, and eventual disposal). A material's life cycle impact includes its effects on air quality, water quality and depletion, energy consumption, global warming and climate change, land use and quality, plant and animal habitat, biodiversity, and raw material reserves.

Life Cycle Thinking
Life Cycle Thinking is evaluation and interpretation of the environmental aspects and potential impacts throughout a product's life from raw materials acquisition through production, use and disposal. The general categories of environmental impacts for consideration include resource use, human health, and ecological consequences. For the purposes of this project, the evaluations are made using current tools such as BEES and ATHENA. These tools provide basic impacts in the areas of global warming potential, air pollution indices, water pollution and use indices, primary energy use, material resource use, and solid waste contributions. Comparisons of impacts are within the assemblies identified, based on the aggregate of individual components. Results from individual product analyses are only used when assembly information is unavailable.

Light Shelf
A daylight-enhancement device; an internal and/or external overhang with a reflecting upper surface normally above head height. Designed to reduce glare near the window and improve illuminance uniformity along an axis normal to the window wall (from Window Systems for High-Performance Buildings, John Carmody, et al.)

Light Tube
An insulated shaft built to direct the light from a roof window or skylight through the attic to the room below. (from Window Systems for High-Performance Buildings, John Carmody, et al.)

Light Sensor
A light sensor is an alternative to the light switch. Light sensors can either be motion or light activated. Motion activated switches turn a light on when there is movement in a space (indoor or outdoor) and switch a light off when no motion has been detected for a period of time. Light activated sensors can be used as alternatives to timers, especially for outdoor lighting or in areas that receive a lot of daylight. Light activated sensors switch lights on when the level of light has decreased to a set threshold and switch lights off when daylight exceeds that threshold.

Light Trespass
Misdirected or poorly controlled outdoor lighting that creates unwanted illumination of adjacent property.

Linoleum flooring is made from organic and renewable resources; for example, the cork used in its manufacture comes from the bark of trees and renews yearly. There are a few concerns about VOCs emitted from some of the natural resins, wood, and linseed oil that make up linoleum. However, these materials provide the bactericidal properties that make linoleum an excellent choice for kitchen areas. VOC emissions can be controlled by factory-applied coatings now provided by some manufacturers. Linoleum requires minimal maintenance and cleans with water in most cases. Use low-VOC adhesives, cleaners, and finish coatings.

Livability refers to the suitability of a place for health and safe human occupation or habitation.

Livable Basement
Indoor air quality issues in basements are a particular concern since the space is located below grade where it is more susceptible to water, moisture, and soil gases which can negatively impact air quality and habitability. Providing and maintaining a healthy indoor environment in the basement includes strategies for design, construction, and occupation. Design and construction strategies include water managed foundations that keep rain away from the foundation wall perimeter (including strategies above grade such as gutters, overhangs, down spouts, and grading to slope away from foundations) and numerous construction strategies to optimize groundwater drainage away from the sub-grade foundation walls (from grading to drainage, damp proofing, and detailing of the foundation walls, footings, and concrete slab). In addition, soil gas construction methods and ventilation systems should be addresses to control possible admission of radon, water vapor, herbicides, methane, or other toxins out of the basement.

In addition, a livable basement should include windows for sufficient daylighting, fresh air, and egress. While design and construction strategies can help to minimize possible health related issues in basements, the homeowner needs to maintain a healthy environment during occupation. Homeowners should eliminate or minimize activities and materials that can cause indoor air quality problems. Since moisture is a great concern in basements, it is especially critical to eliminating or minimizing porous materials in basements. This includes carpet and porous fabrics that may provide possible "sinks" for moisture that can facilitate growth of mold and mildew and subsequent indoor air quality issues.

A house with an office or studio attached or within that serves solely as a place of work for the home owner. The work space typically has a business entrance, independent from the homes entrance.

Living Machine®
The Living machine was developed by Dr. John Todd of the non-profit, Ocean Arks International. It is a wastewater treatment system that relies on natural processes to filter and clean water so that the outgoing water is clean and safe to use for non-potable functions. Wastewater passes through a series of tanks, each with a wide array of specially selected plants, bacteria, fungi, snails, clams, and fish to digest the organic pollutants in wastewater. By treating wastewater onsite, Living Machines can substantially reduce the burden placed on municipal wastewater treatment facilities. They also prevent ground and water pollution from storm sewer overflows or septic tank leaks. Because water exiting the Living Machine can be reused, the demand for municipally-purified water is also reduced.

Low Maintenance Landscape
Landscape that require little or no additional watering, weeding, pruning, cutting/trimming, or other maintenance.

Low-E (Low-emittance) Coating
A microscopically thin (less than 100 nm) metal, metal oxide, or multilayer coating deposited on a glazing surface to reduce its thermal infrared emittance and radiative heat transfer. near-infrared emittance may also be reduced depending on whether solar heat is to be rejected or admitted. Low-emissivity glass is used to increase a window's insulating value, block heat flow, and reduce fading. (from Window Systems for High-Performance Buildings, John Carmody, et al.)

Low-VOC is a low level of volatile organic compounds. Jump to the VOC page for more information.

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Massing refers to the overall size, shape, and volume of a building.

Master Plan
A comprehensive plan for a neighborhood or region intended to set goals and guide development. Goals may include economic development, transit, mix of house types, density levels, and may address issues of aesthetics and sustainability.

Material Safety Data Sheet (MSDS)
A MSDS contains important information about a hazardous material including its name, hazardous components, potential physical and health hazards, permissible exposure limits (PEL), carcinogenic factors, procedures for safe handling, storage precautions and disposal guidance, and other special instructions.

Metal Roofing
Metal roofing is available in two types: panels and shingles. They are made either from steel or aluminum, some with recycled content. Warranties of 50 years or more are common among metal roofing manufacturers. Metal shingles are often used to emulate clay tiles or slate shakes, but are far less expensive and much lighter (requiring less structural support for the roof) than either of these options. Metal roofs can be painted with light pigments and colors to reflect as much as 70 percent or more of the sun's radiation, reducing thermal gains from the roof*. Unlike asphalt shingles, metal roof systems will not support fungi growth. (Professional Roofing Magazine, December 2003)

Microclimate is a highly localized climate that is different from general climate conditions. Microclimates often occur around buildings, or on one side of a building, due to blocking of winds and the trapping of heat form the sun.

Microhydropower is a term used to describe very small hydropower systems. The definition of microhydropower varies, but is generally below 300 kilowatts. At this size, the system can be operated as a "run of the river" installation, without the need for significantly altering the site with dams for water storage. Microhydropower systems use water pressure to move a mechanical device (the turbine), which then drives a generator to produce electricity or performs work directly. The advantages of microhydropower systems are that they run continuously and the energy produced is predictable. (from "Clean Energy Choices: Tips on Buying and Using Renewable Energy at Home." U.S. Dept of Energy, Office of Energy Efficiency and Renewable Energy, 2007. www.eere.energy.gov/solar/pdfs/27684.pdf)

Mixed-use development locates residences, offices, retail establishments, and commercial functions within close proximity to one another—usually walking distance. Mixed-use projects can be organized vertically with shops and offices below housing in a multi-floor building, or horizontally with house and shops detached from each other.

Modular Boilers
A series of small, independently run boilers (instead of one or two large boilers) that maximizes efficiency. They provide the opportunity to start heating a structure as the season turns with only one boiler running. As the winter gets more severe, additional units are brought online. By running at full capacity, the boiler is its most efficient; this creates a 15% to 20% fuel savings. Commonly a large boiler system needs to be oversized to compensate if one needs to be taken offline. With modular boilers, a unit can be taken offline for cleaning or maintenance and the other units will cover the heat load. (adapted from Mechanical and Electrical Equipment for Buildings, 10th ed. Benjamin Stein, et. al. 2006)

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Native Plants
Native plants are particularly adapted to a region's geography, hydrology, and climate since they have evolved and adapted over thousands of years to a particular area.

Natural Ventilation
Natural ventilation or passive cooling uses seasonal breezes and air movement to cool a room or house.

NFRC (National Fenestration Rating Council)
NFRC is a non-profit, public/private organization created by the window, door and skylight industry. It is comprised of manufacturers, suppliers, builders, architects and designers, specifiers, code officials, utilities and government agencies. NFRC provides consistent ratings on window, door and skylight products. www.nfrc.org

Nontoxic or Low-toxicity Materials
Nontoxic or low-toxicity materials are materials that have no or low impact on human health.

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Oriented Strand Board (OSB)
OSB is a wood sheathing material similar to plywood. It is typically manufactured from small diameter, fast growing trees. Unlike waferboard, it is manufactured with the wood chips, or fibers, oriented to provide maximum strength. For quality control, OSB panels should bear a stamp of the Structural Board Association (SBA) or TECO identifying them as structural-rated sheathing. OSB should not be used as siding or in other applications where it will be subject to prolonged exposure to moisture.

Outdoor-Indoor Transmission Class (OITC)
A single-number rating calibrated for exterior walls and facade elements, such as windows and doors, that are subjected to transportation noises from aircraft, trains, automobiles, and other low to mid-frequency noise sources. The OITC is calculated over the frequency range 80 to 4000 hertz. In general, a higher number blocks more noise. OITC ratings are valuable for evaluating the ability of a wall or window to block out exterior noise, but OITC ratings are not as common as STC ratings.

Overheated Period
The overheated period refers to the time of year when it is hotter than what is normal considered comfortable for people. In Minnesota this period is typically from June through August and early September.

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A mixture of liquid and solid materials, usually opaque, that forms a thick liquid substance which can be applied and which dries to a hard dense surface. Generally it does not sink into the substrate (especially wood or fibers). Jump to the Paints, Stains, and Coatings page for more information.

Passive refers to any system that does not rely on mechanical equipment or artificial energy sources. Passive systems use the natural energy flows of sun and wind.

Passive Cooling
Passive cooling reduces the temperature of a building without active, or mechanical means. Examples include, building orientation, long overhangs or awnings, thermal mass and the use of cross ventilation.

Passive Solar
Passive solar heating utilizes the free energy of the sun to heat a house during cold periods of the year. Passive solar systems do not rely on mechanical devices to harvest the sun's power; they are simple systems of south-facing glazing and thermal mass that collect and store the sun's energy as heat. Well-designed passive solar systems also rely on high levels of insulation to preserve heat gain and carefully placed exterior window shades that reduce unwanted solar gain in the summer. Passive solar systems can typically reduce a home's heating energy use by 20-30% in a Minnesota climate.

Passive Solar Heating
Passive Solar Heating uses radiation from the sun to increase the temperature of a building without active (mechanical) means. Examples of passive solar heating strategies include building orientation, thermal mass, or the addition of a greenhouse or solarium to the southern exposure.

Peak Flow Rate
Peak flow refers to the maximum (and often dramatic) increase water flow rate in streams and other water bodies that occurs after a rain event. When it rains, impervious surfaces like parking lots, driveways, roofs and other areas drain large volumes of water into stormwater management systems such as sewers. Because of the speed at which the curb and pipe system conveys water, after even a small rain event there is a dramatic increase in both the volume and the speed of water that flows into streams. The level of streambed erosion is related to this volume and speed of water of the stream; fast-moving water picks up sediment and conveys it downstream, stripping the sides and the bottom of the streambed. With fast moving water the natural process of sedimentation, the redeposition of sediment, does not occur. Over time, this process results in eroded streams unable to sustain the plant life that typically stabilizes the stream banks. Bodies of water further downstream have a resulting increase in particulate matter.

Peat Moss Drain Field
A drain field component of a septic system constructed of a layer of peat moss. The high water holding capacity of peat moss allows for much better effluent treatment than the standard sand bed, some manufacturers claim 99% bacteria removal.

Permanent Wood Foundation (PWF)
If built correctly, wood foundations can provide a long-term, low-cost alternative to conventional basement foundation types. Since wood is a renewable resource, it is often assumed to have lower environmental effects than other foundation materials. However, use of wood in below-grade conditions requires heavy treatment with chemicals at high, energy-intensive pressures, generally Ammoniacal (ACA) or Ammoniacal Copper Zinc Arsenate (ACZA.) These chemicals have negative impacts during production and application to wood members and may leach into the surrounding soil and groundwater if not adequately sealed from the environment. The perceived durability and efficiency of wood foundations has suffered from inadequate and poorly constructed examples. However, careful attention to waterproofing systems that ensure a moisture-resistant installation and good insulation for improved energy efficiency increase the life cycle term for wood foundations.

A material that permits a liquid (or gas) to pass through. The ground is permeable to water, a concrete sidewalk is not.

Permeable Paving
A paving system that allows water to drain to the ground or a receiving system below.

Photovoltaic (PV)
Photovoltaic convert the radiant energy of the sun into electricity. PV can have battery storage or can be connected directly to the grid (the power company). If grid connected, during power generation the electric meter spins backwards as power is fed onto it.

The solid material which adds color to another material it's added to.

A set of drawings, specifically referring to a drawing which shows the layout of the rooms and functions of a home.

Plywood is made by gluing together thin plies (veneers) of softwood or hardwood. There is always an odd number of veneers and the direction of each ply is at a right angle to the adjacent plies, this gives the material it's strength. The more plies, the greater the strength of the plywood. Plywood is graded for exterior or interior use depending upon the water resistance of the glue used to stick the plies together. Code letters shows this grading on each sheet.

Plywood Sheathing
Plywood is a wood sheathing material made by gluing together thin plies (veneers) of softwood or hardwood. There is always an odd number of veneers and the direction of each ply is at a right angle to the adjacent plies, which gives the material strength. The more plies, the greater the strength of the plywood. Plywood is graded for exterior or interior use depending on the water resistance of the glue used to hold the plies together. Code letters show this grading on each plywood sheet.

Post-consumer recycled material has been recovered from consumer product waste and reintroduced into the new-material stream. This recovery occurs at the end of the expected life span of the material or product. Post-industrial recycled material on the other hand, does not enter the consumer market before being re-introduced to a new-product stream.

Post-industrial recycled material (sometimes referred to as pre-consumer material) is an industrial byproduct of the manufacturing process that is re-introduced into the material stream instead of being sent out as a waste-product. This is a common practice in most industry streams as a cost-saving measure.

Potable Water
Water that is of high enough quality to drink. Also called drinking water, potable water is either high-quality groundwater or is water from other sources that is treated to be safe to consume.

Power Combustion Furnace (or Fan-Assisted Combustion Furnace)
A power combustion furnace is equipped with a fan to induce draft for the purpose of combustion. The fan also blows exhaust gases out of the house, reducing the potential for backdrafting. Efficiencies for this unit type are typically limited to 80 to 82 AFUE.

Prefabricated Components
Prefabricated component are factory assembled parts, such as walls, roof trusses, and some plumbing, that arrive on the building site ready to install. Manufacturing over site built components has several advantages including quality control, reduced cost, and reduced material resources. The disadvantages are a lack of customization, and the potential for long distance shipping of components.

Prime Agricultural Land
The federal government describes prime farmland as "land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops... It could be cropland, pastureland, rangeland, forest land, or other land... It has the soil quality, growing season, and moisture supply needed to economically produce sustained high yields of crops when treated and managed... In general, prime farmlands have an adequate and dependable water supply from precipitation or irrigation, a favorable temperature and growing season, acceptable acidity or alkalinity, acceptable salt and sodium content, and few or no rocks. They are permeable to water and air. Prime farmlands are not excessively erodible or saturated with water for a long period of time, and they either do not flood frequently or are protected from flooding." (from the Code of Federal Regulations, Title 7, Volume 6, Section 657.5, www.gpoaccess.gov/cfr/index.html)

Programmable Set-back Thermostat
An electronic thermostat which can be programmed with a schedule to automatically set back the temperature when occupants are not at home, or during the night time hours. Jump to the Programmable Thermostat page for more information.

Poured Concrete Foundation
A poured concrete basement foundation with installed reinforcement provides a stable, long-lasting construction with high fire resistance and the potential for good moisture control. However, concrete by itself is moisture permeable and a high quality waterproofing system is recommended (petroleum-based in most cases). In addition, exterior insulation is recommended to create an energy efficient assembly and reduce problems with moisture condensation on cold concrete surfaces. Concrete has an inherently large environmental impact, but is an extremely durable and long-lasting construction material, ideal for use below grade. Inclusion of waste products such as fly ash and blast furnace slag reduce the need for cement, and can thereby reduce CO2 emissions and related air and water pollution associated with concrete.

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R-value (R = °F sf h/Btu) is a measure of a material's resistance to heat flow. The higher the R-value, the greater the material's insulating properties, and the better it is at preventing heat loss. U-value is the inverse of the R-value.

Radon is a naturally occurring radioactive gas, and the second leading cause of lung cancer in United States. (U.S. Environmental Protection Agency. www.epa.gov/radon)

Radon Infiltration
Radon infiltration is the leaking of radon into the house through the basement. For more information see www.epa.gov/radon.

Rain Barrel
A rain barrel is a simple device for collecting rainwater that falls onto a building's roof to be used later, typically for irrigation. Instead of discharging directly onto the ground and funneled into a sewer, rainwater traveling through gutters and downspouts empties into a large, covered holding tank. By delaying entry of the stormwater into the landscape and the sewers, stress is reduced on local infrastructures during peak water flow periods. Instead, a slower more deliberate release allows more of the water to enter the local ecosystem while at the same time decreasing the demand for potable water. In addition, rainwater, naturally soft and devoid of harsh chemicals, is actually healthier for plants than most municipal water sources.

A raingarden is a bowl-shaped garden designed to collect and absorb storm water runoff from impervious surfaces such as roofs and parking lots. They are often planted with perennial native plants, which thrive in moist soils. Most rain gardens are designed to hold water only for a few hours and do not have standing water. Jump to the Bioretention page for more information.

Rainwater Catchment System
A system of gutters, pipes, and tanks that captures rain water from a roof, or low lying area. The water is stored and can be used for irrigation or as part of a greywater system.

Range Hood
A range hood can promote high indoor air quality by removing odors, moisture and pollutants that result from cooking and gas combustion. Kitchen exhaust fans should be vented directly to the outdoors.

Recovery is any process that reclaims materials, substances, energy or other products contained within or derived from the waste on site. It includes waste-to-energy composting and other processes.

Recycling is the process of collecting and preparing recyclable materials and reusing them in their original form or in manufacturing processes that do not cause the destruction of recyclable materials precluding further use.

Reuse is the recovery or reapplication of a product or material for uses similar or identical to its originally intended application, without remanufacturing or preparation processes that significantly alter the original package or product. Reuse refers to materials or equipment that are reused on-site.

Roof Monitor
A roof monitor is a raised roof section with glazing on one or more sides. It is used to enhance daylighting.

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Salvage is the recovery or reapplication of a product or material for uses similar or identical to its originally intended application, without remanufacturing or preparation processes that significantly alter the original package or product. Salvage refers to materials that are recovered for reuse off-site and sold or donated to a third party.

Sealed Combustion Furnace
A sealed combustion furnace has intake and exhaust vents that are completely independent from the rest of the building's systems. This air does not interact with the interior air, helping to create a healthier condition inside a building.

A drawing showing a vertical cutaway or view through a house.

Sediment Control Pond
Sediment control ponds prevent excessive eroded sediment from entering and clogging natural waterways. Stormwater runoff is held in a constructed pond designed to filter and settle sediment before water exits the pond. Jump to the Biofiltration page for more information.

SEER (Seasonal Energy Efficiency Rating)
SEER is a measure of cooling efficiency for air conditioning units. The higher the SEER rating number, the more energy efficient the unit is. Current federal guidelines stipulate 10 as the minimum. ENERGY STAR rated units must have a rating of 13 or higher.

SEP (Structural Engineered Panel)
The SEP wall and roof system is built with large, pre-fabricated 1 1/8" thick OSB panels. No dimensional framing lumber is used to support the walls, although a system of standard wood trusses is used to support the roof. The OSB panels are strong enough to bear all loads from the roof and intermediate floors. The panels' factory-sanded finish also forms the interior wall surface, and may be directly painted or stained. An interior layer of drywall can be specified if desired. The exterior of the OSB panel is covered with a thick bitumen waterproofing membrane, followed by layers of rigid insulation board and furring strips for fastening the siding. The furring strips are thick enough to hold the siding off the insulation, creating an air gap for a quick-drying rain screen. No vapor retarder or air barrier is necessary since the panels themselves function as an effective air barrier and vapor retarder.

The SEP system eliminates wall cavities, reducing the potential for condensation in the middle of the wall. The large, precut panels also significantly reduce the potential for air leakage. This results in a tighter, more durable envelope, with better indoor air quality and reduced energy use. Since the insulation is continuous with very few thermal bridges (such as studs), cold spots and drafts are reduced, increasing thermal comfort. The disadvantages of the SEP system include a lack of wall cavities for plumbing, electrical, and duct work. If the OSB panels are not correctly specified, they may contain formaldehyde and offgas VOC's, reducing indoor air quality. Since the system is relatively new, training is required, and a lack of familiarity can lead to mistakes unless careful oversight is practiced.

Sediment Trap
An area where stormwater runoff is temporarily stored, allowing sediment to settle before water is discharged.

Sensible Heat
Sensible heat is heat energy that can be measured by a thermometer. Sensible heat causes a change in temperature. It excludes the energy that is contained in water vapor that is absorbed or released as the water changes phase between liquid, gas, or solid. Total heat is calculated by adding sensible and latent heat.

Sensible Recovery Efficiency (SRE)
For an HRV or ERV, the sensible energy recovered minus the supply fan energy and preheat coil energy, divided by the sensible energy exhausted plus the exhaust fan energy. This calculation corrects for the effects of cross-leakage, purchased energy for fan and controls, as well as defrost systems. This value is used principally to predict and compare energy performance. It does not take into account latent heat, i.e. the heat contained in water vapor/humidity.

SHGC (Solar Heat Gain Coefficient)
The SHGC is the fraction of incident solar radiation admitted through a window, both radiation directly transmitted, and that absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits.

After clothes washing, showers typically account for the greatest indoor water use in a home. Low flow showerheads reduce water use by restricting the flow rate in gallons per minute (gpm). The Energy Policy Act of 1992 requires that showerheads use no more than 2.5 gpm, but new high-efficiency models are available that use significantly less water while maintaining a comfortable flow. Showerheads come in two main types: laminar flow and aerating; however, most low-flow models are aerating.

Sick Building Syndrome
In 1983 the World Health Organization defined sick building syndrome as "an excess of work related irritations of the skin and mucous membranes and other symptoms, including headache, fatigue, and difficulty concentrating, reported by workers in modern office buildings." In sick building syndrome, symptoms can not be traced back to a specific cause, but they occur when in a building and clear when out of the environment. If the symptoms can be traced to a specific cause, it is considered a building related illness. (Wood, Brian A. "Sick Building Syndrome: A potpourri analysis" 1999. http://findarticles.com/p/articles/mi_qa3811/is_199904/ai_n8834877/pg_1).

Silt Fence
A silt fence is used as an erosion control device. Typically made of a geotextile fabric, they are placed at the boundaries of a construction site to prevent soil from eroding. Jump to the Silt Fences for more information.

SIP (Structural Insulated Panel)
The SIP wall and roof system is composed of large, factory-assembled wall and roof panels, pre-cut with holes for windows and chases for wiring. The panels, up to 8 feet wide and 24 feet long, are assembled on site, usually with the help of a crane. Little dimensional framing lumber is used, although windows and doorways greater than 5 feet across require headers, and beams are required to support longer roof spans. Although variations exist, SIPs are constructed with two sheets of OSB or plywood sandwiching a rigid foam core of insulation. The OSB panels are each typically 7/16" inch thick, while the rigid insulation typically varies from 2 ½" -13", depending on the climate and performance requirements. A drainage plane such as tar paper is applied to the exterior before the siding is applied. Gypsum board is typically installed on the interior surface of the OSB. No vapor retarder or air barrier is necessary since the panels themselves function as an effective air barrier and vapor retarder. SIPs are capable of supporting typical loads for bearing walls, intermediate floors and roofs. They can provide both the primary structure and the envelope or they can be used with other structural systems such as post-and-beam construction to provide exterior envelope and insulation.

SIP construction eliminates wall cavities, reducing the potential for condensation in the middle of the wall. The large, precut panels also significantly reduce the potential for air leakage. This results in a tighter, more durable envelope, with better indoor air quality and reduced energy use. SIP systems reduce heating energy use in two primary ways. First, the panels provide continuous insulation with far fewer thermal bridges compared to a typical stud wall. Accordingly, R-values for a 6" SIP wall can be almost twice as high as a typical 6" stud-frame wall with fiberglass batt insulation. Second, the panels create an envelope with fewer seams, decreasing air leakage. The air tightness of a SIP-constructed home can be as low as a third of typical new construction. These properties also increase thermal comfort of the home by eliminating cold spots and drafts. The disadvantages of SIP construction include lack of familiarity in the construction trades, higher first costs compared to standard stud-frame construction, and increased difficulty making changes such as re-locating or re-sizing doors and windows. SIPs also have higher embodied energy than stud-frame construction from the manufacturing process.

The placement and orientation of a structure on the land, often to take advantage of the benefits of a particular site—such as views, natural ventilation, passive heating, or daylighting, while avoiding challenges such as poor soil or drainage conditions.

Slab-on-grade Foundation
A slab-on-grade foundation can be a low-cost foundation choice. A conventional slab foundation in Minnesota requires a foundation wall and footing extending below frost depth. Rigid insulation is placed vertically inside or outside the stem wall and horizontally beneath the slab. An alternative that saves material and cost is a frost-protected shallow foundation with rigid insulation extending horizontally out from the slab edge. The main drawback of a slab-on-grade foundation is that many people perceive this option as a lower quality foundation with a floor that is harder and colder than a wood floor. Another consideration is that a slab-on-grade foundation can reduce the street presence of the house as compared to surrounding houses with floors raised above grade. A wood floor raised above grade may be more appropriate in an inner-city neighborhood where it responds to the scale and street elevation of neighboring houses. Other issues with slab-on-grade foundations include the need to place all utility and storage functions above grade, and the inaccessibility of ducts, pipes and wires installed below the slab.

Social and Cultural Factors
Factors relating to ethnicity, economic situation, or religious beliefs which impact patterns of living within a house.

Solar Hot Water
Solar hot water refers water heated through direct solar energy. A number of system types are readily available, including active and passive systems, and flat panel an evacuated tube collectors. Solar hot water can be used for domestic hot water or space heating with radiant systems.

A measure of perceived loudness of a sound. A one sone sound is roughly the level of noise that a refrigerator makes when it is running; four sones is the average TV volume. The sound of a jackhammer from 3 feet has a rating of approximately 60 sones.

Sound Transmission Class (STC)
A single-number rating of a material's or an assembly's ability to resist airborne sound transfer at frequencies between 125-4000 Hz (125-4000 Hz is consistent with the frequency range of speech). In general, a higher STC rating blocks more noise from transmitting through an assembly. The STC rating does not assess low frequency sound transfer - such as mechanical equipment or bass music - which can travel more easily through structural materials via vibration.

Sprawl is a land use pattern that has developed in the last fifty to sixty years. It refers to an increased use of large tracks of land for low-density developments. These often border large urban centers, with clusters of large commercial areas surrounded by vast tracks of single family homes. The downside of this mode of development is a drastic increase in vehicle miles traveled, a decrease in walkability, as well as a loss of agricultural land and native wildlife habitat.

A mixture of solid and liquid substance applied especially to wood that penetrates the surface and imparts a rich color. Opaque and semi-transparent are available, in addition to the traditional transparent application. Jump to the Paints, Stains, and Coatings page for more information.

Standard Framing (2x4 and 2x6)
The 2x4 and 2x6 frame wall at 16" o.c. are standard framing systems. 2x6 at 16" or 24" o.c. is often used in residential construction in Minnesota to meet current building codes and performance standards. This wall system includes siding, oriented strand board (OSB) sheathing, 2x6 wood studs, single bottom plate, double top plate, R-19 fiberglass insulation, vapor retarder, and ½" inch gypsum board. The advantages of this method include familiarity by the trades, easily available products, and the ability to achieve a relatively high R-value. The disadvantages of this system include the use of more material than necessary to meet engineering requirements, and the additional time required for framing (as compared to some other systems—see advanced framing).

Storm Sewer
A network of sewer pipes to carry excess storm water away from streets, often draining into a nearby water body such as a lake or river.

Traditional stucco is a cement-based plaster (a mixture of Portland cement, lime, sand, and water) applied in three coats. Synthetic stucco, used in exterior insulation finish systems (EIFS), replaces the cement and lime found in traditional stucco with a polymer base. It is typically applied in two coats, with a thin fiberglass mesh embedded in the base coat. Hybrids of these two systems include traditional stucco with polymer additives and synthetic topcoats added over thick, traditional base coats. Due to the integral color in stucco's topcoat, painting is unnecessary. Stucco may be painted, but once it has been painted, that coating needs to be maintained to remain attractive. Stucco is long lasting and has low maintenance requirements. Moisture can be a problem with stucco, especially with synthetic stucco, which is less moisture-permeable than traditional stucco. Adequate flashing and drainage detailing are essential to the durability in any stucco wall finishing system.

A sub-floor is the bottom most layer of a floor. The sub-floor is typically not seen, because it is hidden by the finished floor, which can be carpet, wood, or tile, etc.

Sustainable Forestry Initiative
www.sfiprogram.org was developed by the American Forest & Paper Association (AF&PA), supported by major producers and manufacturers, with its own set of criteria and management practices.

A swale is a shallow, often marshy, depressed area of land that accepts stormwater and allows it to slowly infiltrate into the ground. A swale may be designed as a conduit that slows down stormwater and carries it to a larger man-made or natural retention area where it can be filtered by plants as it infiltrates. Jump to the Bioretention page for more information.

Sweat Equity
Sweat Equity describes the labor contributed to a residence by the current or future homeowners for which they do not get paid. Instead, their improvements increase the value of their home and their investment. This is an effective strategy when a goal is to increase the affordability of a home. These tasks can include finishing work such as painting, trim work, and finishing out a basement.

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Task Lighting
Light used to illuminate visually demanding activities, such as reading. (from Window Systems for High-Performance Buildings, John Carmody, et al.)

Thermal Bridging
Thermal bridging refers to an area of the building with a lower R-value than surrounding areas that conducts heat across the building envelope. A steel stud or uninsulated window frame can act as a thermal bridge, undermining the overall thermal efficiency of the building.

Thermal Mass
The mass in a building (furnishings or structure) that is used to absorb solar gain during the day and release the heat as the space cools in the evening. (from Window Systems for High-Performance Buildings, John Carmody, et al.)

Third Party Certification
A third-party is an "independent organization with expertise to provide an assessment and verification of the company's compliance with standards and/or legal requirements." This ensures that vested interests are kept out of consideration when evaluating products and services. (from Tanner, Bob. "Independent assessment by third-party certification bodies." Food Control. 11 (2000) 415.)

Threatened or Endangered Species
Threatened or endangered species are indexed on Federal and State threatened and endangered lists

Toilets account for a significant share of the indoor water use in a home. In particular, toilets manufactured before 1992 are very inefficient, using 3.5 to 7 gallons of water per flush (gpf) while modern toilets use at most 1.6 gpf. As so much water is used in toilets, even small decreases in water use can amount to significant water savings. High efficiency toilets (HETs) are available now that use 1.28 gallons per flush or less. A recent advancement in toilet design has been the dual flush model which has two flush settings: one for solid waste and one for liquid waste. The liquid waste flush usually uses 0.8 gpf, while the solid waste flush usually uses 1.6 gpf. These toilets achieve the criteria for HETs with an average flush volume of 1.28gpf or less.

Topography is the shape of the ground, its rise and fall or elevation changes.

Total Recovery Efficiency (TRE)
For an HRV or ERV, the total energy (enthalpy) recovered minus the supply fan energy and the preheat coil energy, divided by the total energy (enthalpy) exhausted plus the exhaust fan energy. This calculation corrects for the effects of cross-leakage and external purchased energy for fans and controls. It is used principally to predict and compare energy performance. It does take into account latent heat, i.e. the heat contained in water vapor/humidity.

The process by which plants take up water from the soil and release it into the air as water vapor.

Trickle Ventilator
A trickle ventilator is an operable vent in a window or door that allows outdoor air to slowly enter the building. It can be used a supplemental fresh air source.

Triple Glazing
A window with three panes of glass or two outer panes of glass with a suspended plastic film in between. The layers are separated by two gas-filled spaces (usually Argon or Krypton) to increase energy efficiency and provide other performance benefits. (from Window Systems for High-Performance Buildings, John Carmody, et al.)

A lawn or manicured landscape

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U-value (U-factor)
A window's U-value is a measure of the heat flow through a window. The lower the U-value, the smaller the heat flow and the more insulation the window provides. U-value is expressed in units of Btu/°F sf h and is the inverse of R-value. Thus, a window with a U-value of 0.25 has an R-value of 4. Beginning in 2010, ENERGY STAR-rated windows for Minnesota must have a U-value of 0.32 or less.

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Vapor Retarder
A vapor retarder is any material or assembly of materials that resists the flow of water vapor by reducing diffusion. A material that resists vapor diffusion is said to be impermeable, while a material that allows vapor diffusion is permeable. The unit of measurement typically used in characterizing permeability is a "perm." Many building codes define a vapor retarder as a material that has a permeability of one perm or less.

A vapor retarder should not be confused with an air barrier, which is a material or assembly designed to prevent the flow of air. Since water vapor can move through a wall or roof by both diffusion and air movement, it is important to control both with the installation of an air barrier and a vapor retarder. However, it is important to note that air flow transports many times more water vapor than diffusion under typical climate conditions. Therefore, preserving the continuity of the air barrier is significantly more important in reducing the flow of water vapor through exterior walls and roofs than the presence of a vapor retarder. Confusion regarding vapor retarders and air barriers exists because the two are sometimes combined in one material. A common example is 6 mil polyethylene sheeting, which is used with varying effectiveness in stud-frame construction as both the air barrier and vapor retarder. Alternatively, a building house wrap such as Tyvek is permeable to water vapor but not air flow, allowing exterior walls to dry out through diffusion but not by air movement. The house wrap therefore acts as an air barrier, not a vapor retarder.

The liquid portion of a finishing material consisting of the binder and volatile thinners as contrasted to the pigment or solid matter.

Vehicle Miles Traveled (VMT)
VMT refers to the number of miles traveled by residential vehicles over a given period of time. The form of the built environment can have a huge impact on VMT. Neighborhoods and suburbs that are remote from employment centers and public amenities increase VMT per capita while dense, walkable neighborhoods and efficient public transit and other alternative transportation opportunities can dramatically reduce VMT.

Ventilation Types
There are three basic strategies or types of ventilation used in residential construction: exhaust only, supply only, and balanced ventilation. Exhaust only ventilation is common in older, leakier homes. Air is removed mechanically from polluted areas, typically with a bathroom fan or kitchen hood. Make-up air (fresh outdoor air to replace the air that is exhausted) is allowed to "leak" in uncontrolled through cracks in walls and around windows. This type of system typically creates a negative pressure in the house, which can cause backdrafting and draw soil gases such as radon into the home. Supply only is essentially the opposite of exhaust only. Fresh air is mechanically brought into the home using a small fan. This air is typically added to the supply air that is warmed or cooled by the HVAC system before being distributed in ducts throughout the house. Since this creates a positive pressure in the home, air is pushed out of the home through cracks in walls and around windows. In the winter, this can create mold and moisture issues in exterior walls as warm humid air is continuously pushed into cold cavities and cracks in the wall, where it can condense as liquid water. Balanced ventilation mechanically supplies fresh outdoor air and exhausts stale indoor air in equal quantities. These air streams run through separate duct systems, but may exchange heat if the balanced ventilation system includes an HRV or ERV. Balanced ventilation is preferred in new construction and renovations because the ventilation system does not contribute to positive or negative house pressure, and the path of the fresh-air is known, controlled, and can be filtered if desired. Furthermore, a tight building envelope combined with a balanced ventilation system incorporating an HRV or ERV is the most efficient way to ventilate a house.

Vinyl/PVC (Polyvinyl chloride)
PVC siding was first introduced in the 1950's, and since then has steadily increased its share of the residential siding market. "Today, more vinyl siding is produced than any other type of residential siding," (EBN, July/August 1997) and in 2003, over 4 billion square feet of vinyl siding was produced in the United States (Vinyl Siding Institute). Vinyl is inexpensive, easy to install, durable, and needs little maintenance. These attributes make vinyl products seem like the ideal material. However, chemicals used to manufacture PVC products, as well as those given off during its burning and disposal, have proven hazardous to human and animal health, as well as the environment.

Vinyl flooring
Whether as sheet goods or tile, all vinyl products are made from petroleum-based materials and chlorides. Various additives increase durability, flexibility and range of color, but also increase VOC levels and off-gassing. In general, the materials used to produce vinyl products are some of the most toxic pollutants and have significant impacts throughout their manufacture, product life and disposal. Some vinyl products may flake off lead, cadmium, organotins, and phthalate plasticizers. Vinyl also poses a fire hazard, releasing gases such as hydrogen chloride which turns to hydrochloric acid when inhaled. Burning, whether accidentally or in waste incineration, also releases dioxins, which are persistent environmental pollutants. Vinyl products require adhesives, surface coatings and a higher level of maintenance in general over their life cycle compared to many other resilient flooring products. Use low-VOC adhesives, cleaners, or finish coatings to reduce impacts.

Visible Transmittance (VT)
Visible transmittance is an optical property that indicates the amount of visible light transmitted through the glass. VT is expressed as a number between 0 and 1. The higher the VT, the more daylight is transmitted. A high VT is desirable to maximize daylight.

VOC (Volatile Organic Compounds)
VOCs are organic solvents, including paint additives, aerosol spray propellants, and many other building materials. VOCs affect human health and the environment. They are common in many conventional building products and interior finishes. VOCs can cause health problems for residents ranging from eye, nose, and throat irritation to headaches and nausea. They are also linked to cancer and damage to the liver, kidneys, and nervous system. Specifying products that have minimal chemical emissions and emit low or no VOCs and installing materials with minimal VOC-producing compounds contributes to a healthy indoor environment for residents.

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Warm Edge Spacer
The panes of a double-glazed window must be held apart at the appropriate distance by a spacer. Typically, this spacer is made from aluminum because of its high strength. However, a standard aluminum spacer conducts a disproportionate amount of heat through a window unit and, to some extent, negates the benefit of high-performance glass. Increasingly, manufacturers are using warm edge spacers made from a variety of materials including different metals with thermal breaks, thermoplastic, fiberglass, and even high-strength foam. Warm edge spacers slightly improve the U-value of a window, but have a much greater impact on a window's condensation resistance. A warm edge spacer significantly increases the interior surface temperature at the bottom edge of the window glass, in the range of 6-8°F at an outdoor temperature of 0°F. (Efficient Windows Collaborative, http://www.efficientwindows.org/spacers.cfm, accessed 11/09) This nearly eliminates the potential for condensation except for extremely low outdoor temperatures or very high indoor humidity levels.

Water heater heat pump
A water heater heat pump heats water by extracting energy from air or a ground.

A watershed refers to a geographic area that shares a receiving body for rainfall runoff. This area can be a small-scale watershed such as the area drained by a stream, or refer to a large-scale watershed, such as the area drained by the Mississippi River.

Generally, wetlands are lands where saturation with water is the dominant factor determining the nature of soil development and the types of plant and animal communities living in the soil and on its surface (Cowardin, December 1979). Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation, and other factors, including human disturbance. Indeed, wetlands are found from the tundra to the tropics and on every continent except Antarctica.

For regulatory purposes under the Clean Water Act, the term wetlands means "those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas." (from U.S. EPA, Code of Federal Regulations, www.epa.gov/owow/wetlands/what/definitions.html)

Whole House Fan
A whole house fan is a large fan installed in the ceiling of the uppermost story of a house, used to draw air warm air out of the house.

Wildlife Corridor
The natural migratory pathway an animal uses to travel. Corridors can be traveled daily, as animals transverse an area looking for food, or used seasonally for migration.

Wind Wash Barrier
According to the Minnesota Energy Code, a wind wash barrier "... means a material or combination of materials, rigid or flexible, to resist the passage of unconditioned air into the building envelope. Wind wash barrier materials must be suitable for exterior conditions. Flexible wind wash barrier materials must meet ASTM E1677."

Wood is a renewable building material and the forests in which it is grown provide diverse ecological habitats. It is energy-efficient to produce, very little waste is produced in its manufacture (since waste wood is often used for other manufactured wood products), and it is biodegradable. How forests are managed has a significant impact on the environment. Non-sustainable forestry practices result in soil erosion, loss of biodiversity, and other environmental concerns.

Wood Roofing: Shakes and Shingles
Typically Western Red Cedar, Eastern White Cedar, and Alaskan Yellow Cedar are used for wood shake and shingle roofing. Wood shakes are split by hand for a rougher look, while wood shingles are machine sawn. Since they absorb moisture easily, wood shakes and shingles must be installed over furring strips in order to provide the necessary air space for drying. Finishes and stains can be applied to reduce weathering and decay. Untreated shakes or shingles will often weather to shades of silver, gray, or brown. Mildew, moss, algae, and lichens can grow on wood shingles or shakes, keeping the wood moist and accelerating decay. Chemical treatments can be used to clean wood shingle or shake roofs, but they should then be treated and sealed to deter further decay.

Wood Siding
Western Red Cedar, Redwood, Cypress, Northern White Cedar, and Eastern White Pine are the wood species most commonly used for wood siding. The most common types of wood siding are bevel lap siding, shiplap, board-and-batten, and shingles. Wood is a renewable building material and the forests in which it is grown provide diverse ecological habitats. It is energy-efficient to produce, very little waste is produced in its manufacture (since waste wood is often used for other manufactured wood products), and it is biodegradable. How forests are managed has a significant impact on the environment. Non-sustainable forestry practices result in soil erosion, loss of species diversity, and other environmental concerns.

Wood I-joist floor system with OSB decking
A wood I-joist floor system replaces solid wood beams (typically 2x10's) with pre-fabricated I-beams made with engineered wood products. The I-beam's vertical flange is made from OSB while the top and bottom flanges are typically solid wood 2x3's. Since the I-beam is a very efficient shape and the OSB can be made with low-grade or waste wood, very little dimensional wood is used and the I-joist system reduces harvesting of old-growth and large-diameter trees to a minimum. This reduces the environmental impact associated with logging. Despite the energy-intensive OSB manufacturing process, an I-joist's embodied energy and global warming emissions are still slightly less than solid wood beams and wood trusses. However, the OSB contains higher levels of toxins such as formaldehyde and other VOC's. Construction benefits include light weight and a greater spanning capability than solid wood beams (up to 26 feet typically).

Wood I-joists Roof
Wood I-joists used as rafters in roof construction provide a flexible, resources efficient alternative to solid wood. I-joists are an engineered wood product made by bonding a top and bottom wood flange to a web of oriented strand board (OSB). In construction, joists can be spaced 16" or 24" on center depending on load and I-joist depth. I-joists provide consistent structural performance for residential applications. They can span long distances and are lightweight, simple to install, dimensionally stable, and easy to handle.

Wood-resin Composite
Wood-resin composite siding is a manufactured wood based product. It is produce by mixing synthetic resins and wood dust, which are put into a die form press, and compressed under high temperatures. The resins reduce the risk of moisture damage. Wood-resin composite products can still be at risk of damage due to moisture, to prevent moisture damage most wood-resin composite siding is installed with ventilation spacers or furring strips behind the siding to permit drying.

Wood truss floor system with OSB decking
A wood truss floor system replaces solid wood beams (typically 2x10's) with pre-fabricated trusses made from 2x4's. By using smaller dimension wood, the trusses reduce harvesting of old-growth and large-diameter trees. This reduces the environmental impact associated with logging. However, compared to solid wood beams, extra energy and pollution is involved in manufacturing the trusses. Construction benefits of using prefabricated trusses include less job-site waste and easy routing of ductwork and pipe through the floor cavity. In addition, floor trusses can typically span 30 feet or more, 50% farther than solid wood beams made from Douglas Fir.

Wood Truss Roof
A wood truss roof is constructed of pre-engineered and pre-fabricated wood trusses. Typically constructed with 2 x 4 members and nail plate connectors, they are the most common roof construction system used in the residential market. Factory assembly and use of small members makes this structural system resource efficient. Roof trusses are available in standard pitches and dimensions; they can also be customized. Raised heel trusses have a taller "heel" where they rest on the perimeter wall. The extra height (usually around one foot) allows the full thickness of attic insulation to extend to the wall perimeter.

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A type of landscaping that uses plants with low and no water needs.

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Zero-VOC is the absence of volatile organic compounds.