Last Updated: Jul 22, 2021
Roofing is sometimes overlooked when considering sustainable home projects. But, roofs are a major part of the home and deserve consideration when the time comes to replace them. As with many products, some are "green" simply because they are better than the alternative. Many of the most popular roofing products on the market today are better than those used in the past. These new materials last much longer, and some can be recycled.
More sustainable roofing options last longer than average, can be recycled at the end of their lives, have lower embodied energy, or are sourced from non-mined or fossil fuel-based materials. Below, we look at some of the most popular roofing products before turning our attention to the top five more sustainable roofing options available today.
The vast majority of roofs in the United States are made of asphalt shingles. Asphalt shingle roofs are the preferred option for most homeowners because of their low upfront cost and relative ease of installation. So what's the problem? First, durability. Many asphalt roofs only have an estimated lifetime of between 15 and 20 years. This means that homeowners will most likely have to invest in a new roof at least 2-3 times during the home's lifetime. Second, asphalt shingles are estimated to make up 5% of the total construction-related waste each year, to the tune of 11 million tons of asphalt shingles thrown out each year. In context, a 2020 report conducted by the EPA, stated that 17% of construction waste to landfill stemmed from roofing materials. Even though asphalt shingles can be recycled, these shingles' raw material contains polycyclic aromatic hydrocarbons (PAHs), a known carcinogen. Asphalt shingles contain bitumen, which is a petrochemical and thus, a non-renewable material.
Metal roofing is another popular roofing option and is growing in popularity in North American home construction. While these roofs are extremely long-lasting and durable, they have a high embodied energy rating. Aluminum, the primary roofing material, has a much higher embodied energy rating between 170 and 230 MJ/Kg. For comparison, cement has a rating of 6 MJ/Kg. (Editor's note: embodied energy estimates vary widely. These estimates are based on the sources cited here.) So, while your metal roof might help increase your home's thermal performance and make a steady place to mount your PV panels, there is a lot of hidden energy required to mine, manufacture, and transport this roofing material.
EPDM—Ethylene Propylene Diene Monomer, a synthetic rubber derived from oil and natural gas (ethylene propylene)—is the most common roofing material for homes and commercial buildings with flat roofs. In general, EPDM is marketed as an "environmentally friendly" roofing option. Its dark color helps reduce heating costs in the winter because it absorbs the sun's heat. That is a questionable assumption, though, because the dark hot material increases cooling costs in the summer. This heat absorption adds to the urban heat island effect. In cold climates, it is often covered by snow—eliminating any warming benefit. For hotter climates, EPDM roofs are available in white to reflect rather than absorb the sun's heat. EPDM roofing is recyclable. In addition, the materials used to make EPDM are derived from fossil fuels, and they may only last about 15 years. The longevity of EPDM is variable, depending on climate, care, installation, etc.
Are you planning to build a new home or renovate an older, leaky roof? Take a look at the roofing options discussed below. They all offer unique, sustainable, and more environmentally friendly hats for your home.
Terracotta tiles have been used in housing for thousands of years. This natural roofing option is sourced from a renewable resource (the clay beneath your feet). It can be manufactured locally anywhere clay soil can be found. Terra cotta tiles are extremely durable. A well-maintained roof can last at least 50 years; there are terra cotta roofs that are centuries old in Europe. While this roofing option will most likely cost you a bit more upfront, the fact that this roofing option will most likely last for a lifetime will save money and time in the long run. Unlike asphalt shingles, terra cotta tiles will not warp or decompose, and the color is virtually fade-proof. In terms of energy efficiency, this is one of the most highly insulating roofing materials on the market. While you will need to apply a waterproofing sealant periodically, maintenance considerations are otherwise low throughout the year.
Sod roofs have been used by different cold-weather cultures worldwide (and especially in Scandinavia) for hundreds of years because of their high insulating properties. With this type of roof, your home will benefit from the insulation that a layer of soil and grass or plants provides. While you will need to install a waterproof polyurethane membrane (such as pond liner), all other parts of a living roof can be sourced from renewable resources. The aesthetics of a green roof can be beautiful. The plant growth will actively sequester carbon from the atmosphere, making your roof a carbon-negative element of your home.
Cedar-shingled roofs are beautiful, and when properly cared for, can last a lifetime. With proper maintenance, cedar shingles or shakes could last upwards of 30 years. Double the average lifespan of asphalt shingles! When a cedar shingle roof does need replacing, these natural shingles can be passed through a wood chipper and applied to your garden as mulch. With this excellent option, you avoid the need to ship large volumes of non-renewable roofing materials to the local landfill.
One of the most expensive roofing options on the market is slate roofs. While the main disadvantage of this elegant stone roofing material is its upfront cost, there are numerous benefits. First, durability: the estimated lifespan of slate tiles is 200 years. The natural color variations of the different colored rocks will give your roof a truly unique appearance. Other benefits of slate roofing include inherent fireproof qualities, zero VOCs or other pollution during the manufacturing process, and excellent thermal performance that can help lower your energy bills.
Over 290 million car tires are discarded each year in the United States alone. Many of those tires end up in landfills. However, a few innovative companies turn those tires into rubber roof shingles made to look like slate. EcoStar is one company producing such shingles. Their Seneca Shake Shingles line looks like cedar shingles but is made from 80% post-industrial recycled materials. In addition, they come with a 50-year warranty. These unique recycled shingles are a great way to recycle used tires into a durable roofing alternative.
While roofing is usually an afterthought in the design, planning, and construction of sustainable buildings, these five more sustainable roofing options will allow you to increase the durability and resiliency, as well as decrease the carbon footprint of your home.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.