The Low Down On Green Living
April 6th, 2008
As a passionate green designer, I find few things more boring or environmentally-challenged than standard asphalt shingles on a residential roof. Thankfully there are lots of green roofing materials that have a variety of eco-friendly attributes such as being Energy Star rated or containing recycled content. Oh and by the way, they look great too!
In this piece we’ll focus on roofing material selection rather than on alternative roofing systems such as green (living) roofs or solar PV roofing tiles. You can read more about green roofs in this recent blog posting, and we’ll soon be doing a piece on solar roofing tiles.
When considering a new roof, the two key dimensions you should think about are the material and the color (and, of course, cost!).
First, Materials. A high performance roofing material coupled with a well insulated attic will help to keep your home warm in the winter and cool in the summer. Your roofing material is the final layer of protection from the outdoor elements and from indoor heat loss. When deciding what’s green and what’s not, you should consider several aspects of a given material. These include the raw material source and composition, durability / life cycle, maintenance, and disposal. Often there are tradeoffs: a very durable and efficient material (such as metal) might require more energy to produce. Cost and ease of installation are not necessarily green attributes, but will always be factors in your decision.
Next Color. It should be no surprise that a light colored roof reflects heat and a dark roof absorbs it. Due to overdevelopment in urban areas, an abundance of dark colored roofs (often asphalt) can raise outdoor temperatures. Elevated temperatures impact communities by increasing peak energy demand, air conditioning costs, and air pollution levels. Light colored roofs, often referred to as “Cool Roofs”, are roofing materials that have a high solar reflectance rate and thus help to reduce outdoor temperatures and reduce heat transferred into a house. This happens because cool roofs reflect the sun’s energy and keep the roofing material cooler on those hot summer days. If you live in a heating-dominated climate outside of the city, dark roofs may be the way to go since they will capture more of the sun’s energy during cold weather. But in most urban and cooling-dominated places, light is right!
Color is closely related to solar reflectance, which is measured on a scale from 0 to 1, or 0% to 100%. For roofing materials, the higher the value, the more sun reflected and the cooler the roof. This link to ENERGY STAR makes it very easy to select a cool roof and provides a list of products that pass their standards. Approved products must meet minimum initial and aged solar reflectance values in order to qualify. For those of you that want to take it one step further, visit the US Department of Energy website to calculate the impact of your current roof.
We’ll now cover a variety of roofing materials and discuss why they are green or not.
More than 75% of American roofs have asphalt shingles due to low cost, ease of installation, and resiliency. Unfortunately, asphalt shingles have a low insulative value, a shorter lifespan than many other roofing materials, are made from petroleum products (and release pollutants during application) and are often not recyclable due to the layer of fiberglass between the asphalt minerals. Standard asphalt shingles come in a variety of colors, longevity options, and price points. They are always going to be your cheapest option for your roof, but they have the worst environmental track record. They may make sense in the short run, but over the life of your roof many of the options below are better for the environment and for your savings account.
Wood shingles, such as cedar shakes, are natural, have twice the insulative value of asphalt, and become more beautiful as they age. However, wood is expensive to purchase and install, and it often doesn’t pass fire code unless treated with toxic fire retardent chemicals, which defeats the original intent of using wood. The natural swelling and shrinking of wood can also result in cracks and moisture damage, which will cause decay over time. Historically, many roofing shingles came from old-growth cedar trees, so they were a poor environmental performer. Today, though, you can buy Forest Stewardship Council-certified shingles from companies such as True North Cedar and Koenig Cedar Company.
Metal roofs are some of the coolest roofs around, both in temperature and in looks for homes. Metal roofs are available in copper, aluminum, and stainless steel, and often have a high percentage of recycled content. They have a high insulative value, solar reflectance, and durability, often lasting twice as long as wood or asphalt. They also come in many profiles from standing seam to corrugated. However, metal roofs made from virgin (vs. recycled) metals require huge amounts of energy to transport and manufacture, and metal roofs can be expensive. Some leading manufacturers include Zappone Manufacturing (copper and aluminum shingles from recycled material) and Classic Metal Roofing Systems.
Slate is probably the most durable roofing material, but it can be expensive, with high-end installations ranging between $50 - $100 per square foot. Slate will last a long time, but the fasteners that adhere it to the roof deck will wear out after about 100 years. As a natural material, slate is extremely durable and also recyclable. It comes in a variety of colors and the variation of color is what gives it its unique character. Since slate is extracted from the earth, it is a non-renewable resource, and the embodied energy taking it from quarry to rooftop leaves a large footprint. However, you can find reclaimed / salvaged slate roofing from such companies as The Durable Slate Company and the Roof Tile and Slate Company.
Clay tiles invoke a certain Mediterranean flair, have a lisfespan of 50+ years with good insulative value, and are Class A fire rated. Clay roofing tiles can come in lighter colors which adhere to the cool roof standards and can reflect well over 50% of the sun’s solar energy. Clay roofs are often a little pricier than conventional roofs, but if you like the look and not the price tag, try using them in accent areas like doorway overhangs or only visible areas of the roof. Leading providers of “green” tile products include the previously mentioned Roof Tile and Slate Company, Custom Tile Roofing, and MCA Tile (not reclaimed, but Energy Star / cool roof products).
One last set of options if you like the look of slate or cedar but not the environmental impacts are new recycled roofing materials that look like their natural counterparts. Companies like EcoStar by Carlisle, Re-new Wood and Authentic Roof have products that contain recycled rubber and plastics, are half the weight of real slate, and have a 50 year warranty. They also have a variety of colors and profiles that look like the real thing.
There are MANY other roofing options out there, so speak with a green builder, preferably one that is familiar with the energy star standards like those found here, for more information on alternative roofing and cool roofs. Don’t be an asphalt– put on a cool roof today!
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