MINNESOTA GREEN AFFORDABLE HOUSING GUIDE

Promoting Sustainable, Healthy, Durable & Energy Efficient Housing

Components: Roofing

Materials

Fact Sheet»

Description

Roofing, whether it is asphalt shingles, metal roofing, wood shakes or shingles, plastic/composite shingles, or fiber-cement shingles, protects a house from the elements. Light colored roofing materials can reduce cooling costs and energy by reflecting the sun's rays and reducing thermal gains. The following analysis examines the relative economic, energy, and environmental impacts of the following roofing options: self-healing asphalt shingles, organic asphalt shingles, fiberglass asphalt shingles, clay and concrete tiles, standing seam metal roofing, metal shingles and tiles, wood shakes and shingles, composite/synthetic (plastic and rubber) shingles, and fiber cement shingles.

Recommendations:

Although asphalt shingles have the lowest first cost, they require more frequent replacement than other options resulting higher lifetime costs. Asphalt shingles also make a significant contribution to landfills. Metal roofing and fiber cement shingles last longer than asphalt shingles without adding weight to the structure. Because metal has high recycled content and can be recycled after use, it has a favorable environmental impact.

In selecting roofing materials, consider the weight and whether additional structure is required. If so, factor the environmental impacts of that increased structure into the overall impacts of the roofing. Also consider how the roofing material affects the quality of water falling on it. For example, will it contribute sediment that may plug gutters or catchment containers?

Roofing Alternatives

alternatives cost/sq. ft. (materials & labor) expected product life (years) life cycle thinking practice
asphalt shingles, self-healing .62 20-35 typical standard
asphalt shingles, organic .72 15-30 typical standard
asphalt shingles, fiberglass .81 15-30 typical standard
clay and concrete tiles not available 30-50 typical trained installers
metal roofing, shingles, tiles, and tile panels not available 50+ good some training required
metal roofing, standing seam not available 50+ better some training required
wood, shakes and shingles 2.61 30, 40-50 good standard
composite/ synthetic (rubber & plastic) shingles not available 40-50+ typical standard
fiber cement shingles 2.21 40-50+ better some training required

Criteria Summaries

Cost: Lower initial cost roofing options, like asphalt shingles, may end up costing as much as higher initial cost roofing options over their life cycle.

IAQ: Roofing materials are 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 construction.

Expected Product Life: Asphalt shingles have the shortest life of any roofing products. Natural slate, clay or concrete tiles, and fiber-cement products have the longest. Metal products, if properly coated and maintained, can also last for decades and are highly recyclable into similar products at the end of their use. Wood shakes and shingles, if properly maintained, will last longer than organic asphalt and most fiberglass shingles and can be composted at the end of their usefulness.

Life Cycle Thinking:

  • Energy consumption (non-renewable, fossil fuel energy):
    Clay tiles, because manufacturing processes require firing, consume the most energy; they are also heavy and require more transportation energy to ship. Concrete, which is a very resource and energy intensive product, also has high embodied energy. Fiber-cement composites, which use fillers such as wood fibers or other waste products, reduce the energy consumption by reducing the amount of virgin cement, concrete, and aggregate material required. If wood or other lower-quality fibers are used in cement products, they reduce total embodied energy. Asphalt shingles, both organic and fiberglass, have a higher embodied energy than wood or composite products, even considering their shorter life cycle. Wood products have the lowest embodied energy of any roofing materials because they come from a renewable source and require less processing before installation. They also weigh less than tiles or shingles and require less energy to transport.
  • Pollutants generated in production: Clay tiles and fiber cement products generate the most pollutants. Producing clay is an energy-intensive process, which generates pollutants through energy used and the manufacturing process of kiln-firing clay to hardness and durability requirements. Because fiber-cement shakes, shingles and panels rely primarily on cement, they generate more pollutants due to the resources used and the process for manufacturing a finished product (cement production and pressing/curing operations.) Asphalt shingles come next in pollutant generation since they are petroleum based.
  • Potential for off-gassing in the building: Because these are exterior products, their effects on the indoor environment are minimal.
  • Durability of the product: Natural slate, metal roofing, and concrete, clay and fiber-cement products have the longest use cycle. Asphalt shingles, both organic and fiberglass, have the lowest use cycle and need to be replaced most often.
  • Potential for future recycling: Metal roofing materials (aluminum and steel) have high recycled content and are readily recyclable, reducing overall higher impacts because of their more closed-loop production cycle. Asphalt shingles may use some recycled content in their paper base, and some manufacturers may use recycled aggregate in their production. Some wood composite products can be ground up and reused or recycled, but many cannot. Plastic-based composites cannot be recycled either. Fiber-cement products have limited recycling use, but can be ground up and reused in fabrication. However, there are no current programs in place to collect and reuse materials, and much of it may end up in landfills.

Practice: Slate, concrete and clay tiles, and fiber cement shingles may require training for installation. Asphalt shingles, wood shingles, and wood shakes are common roofing materials and have standard installation methods.

Environmental Context

Roofing systems with shorter life spans (asphalt shingles and some wood shingles and shakes) generate more negative impacts over time because they must be replaced more often. Although they may have significantly lower first costs, over time they can cost as much as the more expensive products which last longer. Wood products, in general, have lower environmental impacts than metals, but if they come from slow growth forests or non-sustainably harvested forests, the impacts are high as well. Products from certified forests reduce the impacts of erosion, soil loss, and habitat destruction. Natural slate and clay or cement tile shakes are expensive and heavy, often requiring additional structural support; however, they have an extended life cycle, which may reduce their overall impacts, depending on the type of building construction. Asphalt or fiberglass shingles, made from petroleum-based products, have lower first costs, and do not at present contain much recycled content, except in the paper base. Programs for recycling asphalt shingles (into road asphalt as one option) are only recently becoming available at the local level. Fiber-cement products have high embodied energy and create significant negative impacts related to water quality and air and water pollution from their extraction phase through manufacture and transport. They are very durable, however, and where they incorporate waste or low-quality wood fiber products, produce lightweight, long-term installations that reduce those negative impacts.

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