Roofing

In selecting roofing materials, consider their weight and whether additional structure is required. If so, factor the environmental impacts of the increased structure into the overall impacts of the roofing. Also consider whether a particular roofing material is appropriate for the type of roof. For example, many asphalt shingles are warranted for use on cold roofs, but not hot roofs. Cold roofs have a ventilated attic space that is not conditioned or a ventilated air space between the insulation and roofing. Hot roofs include SIP roofs and other roof types without a ventilated air space between the roofing and the insulation. Finally, consider how the roofing material affects the quality of water falling on it. For example, will it contribute sediment that may clog gutters, rainwater collection, or catchment systems?

Options and Analysis

roofing types expected product life (yrs) cost/sf (materials & labor) installed cost/year of expected life/sf global warming potential (lbs of CO2/sf building footprint) Life Cycle Analysis
(per sf)
practice
Asphalt Shingles: Organic 5.6 Primary energy consumption (Btu) 112,015 standard
Solid waste (lbs) 0.8
Air pollution index 1.1
Water pollution index0.001
200 - 230lb 20 NA NA
230 - 250lb 25 $1.20 $0.05
250 - 325lb 30 $1.68 $0.06
325 - 385lb 30+ $2.30 $0.07
Asphalt Shingles: Fiberglass/ Inorganic 3.1 Primary energy consumption (Btu) 41,769 standard
Solid waste (lbs) 0.6
Air pollution index 0.7
Water pollution index 0.001
200 - 235lb 25 $1.26 $0.05
235 - 260lb 30 $1.56 $0.05
260 - 300lb 30+ $2.01 $0.06
Clay Tile 30-50 $4.29 (low end) $0.11 17.9 Primary energy consumption (Btu) 172,617 trained installers
Solid waste (lbs) 2.8
Air pollution index 2.8
Water pollution index 0.001
Concrete Tile 30-50 $4.29 (low end) $0.11 7.2 Primary energy consumption (Btu) 80,579 trained installers
Solid waste (lbs) 0.9
Air pollution index 1.1
Water pollution index 0.001
Metal Roofing: Shingles, Tiles, and Tile Panels 50+ $1.94 (low end) $0.04 4.9 Primary energy consumption (Btu)* 56,934 some training
Solid waste* (lbs) 1.2
Air pollution index* 0.7
Water pollution index* 0.005
Metal Roofing: Standing Seam 50+ $2.55 (not Costworks) $0.05 4.9 Primary energy consumption* (Btu) 56,934 some training
Solid waste* (lbs) 1.2
Air pollution index* 0.7
Water pollution index* 0.005
Wood Roofing: Shakes & Shingles 30-50 $2.44 - $3.10 $0.07 2.8 Primary energy consumption (Btu) 32,855 standard
Solid waste (lbs) 0.5
Air pollution index 0.6
Water pollution index 0.001
Composite/ Synthetic (Rubber & Plastic) Shingles 40-50+ NA NA NA NA standard
Fiber Cement Shingles 40-50+ $2.68 $0.05 NA NA some training

Costs based on Means CostWorks 2007, unless otherwise noted. LCA measures and global warming potential modeled using Athena EIE 3.03
*These LCA numbers are estimates for a steel roof

Operating Energy
Light colored roofing materials can reduce cooling costs and overall energy use by reflecting the sun's rays and reducing thermal gains. This is more valuable in cooling-dominated southern climates or for internal load-dominated buildings, such as office buildings. (Homes are typically envelope load-dominated because their surface area-to-floor area ratios are higher and there are fewer internal heat sources, such as people, lighting, and computers.)

Cost
Lower initial cost options like asphalt shingles may end up costing as much as higher initial cost options over their lifecycle. This is demonstrated with the installed cost per year of expected product life column in the chart above. While standing-seam metal roofing may initially cost twice as much as lightweight asphalt shingles, over the life of the product it is actually cost-competitive at $0.05/sf/year, while asphalt shingle options cost $0.05 - $0.07/sf/year. This is due to the durability and longer service life of the metal roofing. (Note that this metric does not include maintenance costs associated with the product, if any.)

Life Cycle Analysis
(measures are given per square foot of roofing)

(measures are given per square foot of roofing per year of expected life)

Energy Consumption
Concrete and clay tiles require large amounts of energy to manufacture and their substantial weight increases the energy required for transportation. Fiber-cement composites, which use fillers like wood fibers or other waste products, reduce this energy consumption by reducing the amount of virgin cement, concrete, and aggregate material required. They also weigh less than concrete tiles or shingles and therefore require less energy to transport. Comparing organic and fiberglass asphalt shingles, organic shingles have nearly 6 times the embodied energy. When the relatively short lifespan of organic shingles is taken into account, the embodied energy impact further worsens to almost equal that of clay tile. Wood shingles and shakes have the lowest embodied energy because they come from a renewable resource and require less processing before installation. If maintained, they can also have a relatively long service life, further reducing their lifecycle impacts.

Water Pollution
Mining for metal can have long-term negative impacts on surface and subsurface water quality. These impacts vary substantially according to the particular metal deposit being mined, but are often difficult and expensive to address. If metal roofing is used, seek products made with high recycled content to reduce water pollution impacts.

Indoor Air Quality
Roofing materials are an exterior application and do not directly affect indoor air quality. However, installation of these materials may create dust (primarily from fiber-cement products) or emissions of petroleum-based chemicals (asphalt and fiberglass shingles), which may prove allergenic to some individuals with heightened sensitivity. Precautions should be taken to prevent dust or odors from permeating the rest of the house.

Future Recycling
Metal roofing materials (aluminum and steel) have high recycled content and are readily recyclable. This reduces their high initial impacts by closing their production loop. Asphalt shingles may use some recycled content in their paper base and/or make use of recycled aggregate. Recently, recyclers have found a use for shingle scrap and discarded shingles as road base. However, recycling programs for used shingles may not exist locally. Some wood composite products can be ground up and reused or recycled, but many cannot. Generally, plastic-based composites cannot be recycled. Fiber-cement products have limited recycling use, but can be ground up and reused in fabrication. In general, products that mix bio-based materials with inorganic materials (metals, plastics, etc.) are difficult to recycle. Wholly organic materials are compostable and non-hybridized metals and plastics are relatively easy to recycle.

Practice
Fiber cement shingles, concrete and clay tiles, and some standing seam metal roofing systems require special training for installation or certified installers. Asphalt shingles, wood shingles, and wood shakes are common roofing materials and have standard installation methods.

Other Resources

Web Sites

1 Cushman, Ted. "Have Asphalt Shingles Improved?" ServiceMagicPros website. Provided courtesy of Journal of Light Construction. Accessed September 2009.