Is white the new green in roofing options?
Iris Price | Improvement Center Columnist | May 18, 2015
When someone mentions green roofing, do you envision the distant spires of the Emerald City? If so, you might be living just a little too far off the grid. If you said the Hanging Gardens of Babylon, however, you'd be closer to the real thing. True green roofs grow. As for the other kinds of green roofing options, they can be any color, but white is actually the new green.
The meaning of green
Whether you live in the boonies, the 'burbs, or the big city you likely have heard by now about the trend toward green building products and materials. Like other green building options, green roofing must meet one or more of these criteria:
- limited or no health risks
- greater product longevity
- superior energy efficiency
- recyclable to reduce landfill
- manufactured using processes that conserve water
- reduced carbon footprint throughout the product's life cycle
These standards for green building and green products have encouraged manufacturers, builders, architects, designers, contractors, and building suppliers to continually improve the green factor for products and materials they offer for use.
In addition, roofing products may be evaluated for properties such as thermal emittance (how effectively a surface can cool itself) and solar reflectance (the ability to reflect solar energy back into the atmosphere). Rating these properties helps determine a roofing product's relative effectiveness to insulate a building, and at the same time, keep the planet cool. The Cool Roof Rating Council (CRRC), a non-profit educational organization established in 1998, provides test results of performance ratings to roofing surface manufacturers, who may then pass the information on by labeling their products.
Green roofing: options for everyone
Until recently, cost has typically deterred some homeowners from green building and remodeling. The expense of a new roof, green or otherwise, scares homeowners into "going cheap" instead of going green, but the price of green roofing options has started coming down. Manufacturers are streamlining processes as building codes continue to up the requirements for products and building systems that provide better conservation of energy and resources. With this increased demand for green building, supplies are no longer as rare as they used to be. Manufacturers have ramped up production.
As you consider some of the following green roofing options, look at cost also over the lifetime of your roof. Factor in potential energy savings for the same period of time, and weigh the benefits of a product that meets the criteria for green roofing options:
"Green roofs" or "living roofs" refer to roofs that are covered in vegetation ranging from sod to entire gardens. A flat expanse of living roof can improve urban environments not only with its natural aesthetics. It can insulate a home or commercial building and help manage storm water runoff in a community by as much as 65 percent, according to the U.S. General Services Administration (GSA), which manages 2 million square feet of green roofs.
The GSA also maintains that the vegetation on a living roof can cool its surface by 30 to 40 percent and reduce heat transfer from the roof to the building by as much as 72 percent. It can also more than double the longevity of a flat roof. Recent research published in the March 2014 issue of Energy and Buildings, however, finds that the expense of installing a living roof, which is more than other green roofing options, cannot compensate for the energy savings over the extended life of the roof. The study concludes that white roofs actually provide greater cooling potential for Earth's environment and offer a better return on investment during the life of the product.
For buildings in hot climates, a cool roof can reduce the temperature of the roof's surface by 50°F, thereby increasing the comfort of the indoor temperature and extending the lifetime of the roof. Roofing products used today to convert a roof to a cool roof include white paints and other types of coatings that reflect sunlight as well as protect the roof from UV and water damage. Environmental benefits in areas where many buildings have cool roofs include counteracting the "urban heat island effect," by reducing the temperature of an entire community.
There is nothing new about cool roofs. White roofs in hot climates traditionally served the same purpose. However, you should consider a different type of roofing if you live in either a cool or a hot, humid climate. Homes in cool climates with cool roofs lose the benefit of solar heat gain through the roof in winter, and accumulate condensation. Those in hot, moist climates risk mold and algae growth.
You may be considering metal roofs for any number of reasons, including their lighter weight, fire- and pest-resistance, as well as durability. Metal roofs also meet a number of green roofing criteria: longevity -- they can last 40 years or more; recyclabilty; and energy-efficiency. With various coatings as mentioned above, they can qualify as cool roofs. Coatings such as natural stone granules applied to the metal can create the appearance of other types of roofing including shakes and tiles. Stone-coated steel roofing is considered a cool roof because of its reflective and highly emissive properties.
Other types of green roofing
You can choose green options from almost any traditional roofing materials.
- Clay tiles. Look for recycled content; recyclability; local sourcing; sustainability; cool roof-compliant colors.
- Concrete tiles. Traditional concrete contributes up to 10 percent of global CO2 emissions, but you can find more sustainable forms of concrete using recycled materials such as wood chips and crushed glass.
- Green asphalt shingles. Asphalt shingles, popular because they are the cheapest option, are a petroleum-based product. If you plan to use them, choose those with greater longevity, recycled content and reflective coating.
- Solar shingles. Thin-film photovoltaic solar energy cells are now manufactured as roof shingles, so instead of installing solar panels, you can have your shingles produce energy from the sun to lower your power bills.
- Repurposed/recycled materials. Roofing manufactured from recycled rubber tires and plastic keeps these materials out of landfill. The resulting roofing products emulate the look of slate, but are much lighter weight and last as long as clay, slate, concrete, and metal roofs.
When looking for the right green roofing product for your home, ask contractors and suppliers about how the materials fulfill the criteria for green building. If cost is important to you, be sure to calculate what you can save long-term.
Photo credit to Kevin Irby