Are cool roofs affordable? 

Yes.  Many cool roof varieties cost the same amount as other comparable roofing materials, and for those that cost slightly more, the difference can usually be quickly recovered in savings from reduced energy costs.

What is Emissivity?

The emittance of a material refers to its ability to release absorbed heat. Scientists use a number between 0 and 1, or 0% and 100%, to express emittance. With the exception of a metallic surface, most roofing materials can have emittance values above 0.85 (85%). One example is a metal wrench left in the sun, which is hot to the touch because it has a low emissivity value.

Link Between Energy Savings and Emissivity

Solar reflectance is the most important characteristic of a roof product in terms of yielding the highest energy savings during warmer months. The higher the solar reflective value the more efficient the product is in reflecting sunlight and heat away from the building and reducing roof temperature. This is particularly important in areas of the U.S. where peak load is a concern.

Emissivity can also contribute to a cool roof. In warm and sunny climates highly emissive roof products can help reduce the cooling load on the building by releasing the remaining heat absorbed from the sun. However, there is also evidence that low emissivity may benefit those buildings located in colder climates by retaining heat and reducing the heating load. Research on the benefits of emissivity is ongoing. Discuss reflectance and emissivity with your roofing contractor to determine what characteristics matter most given your unique climate.

ENERGY STAR Requirements

ENERGY STAR qualified roof products must meet minimum initial and aged solar reflectance values. Emissivity is not currently a requirement for ENERGY STAR qualification. However, starting December 31, 2007, EPA will post emissivity values for all products on the ENERGY STAR Qualified Products List to assist consumers in their purchasing decision. Longer term, EPA plans to revisit the possibility of adding an emissivity component to the ENERGY STAR specification.

Will I save money by using reflective roof products if my home or building already has a high level of insulation?

An energy-efficient home or building has both reflective roof surfaces and adequate insulation. But, you will notice greater savings on your cooling bills if you install ENERGY STAR qualified roof products on a building with a lower level of roof insulation. However, when installing a reflective roof while constructing a new building, doing a major renovation, or replacing your whole roof system, you should consult with your contractor to maximize savings by making sure an optimum level of insulation is installed.

Can I expect the same level of savings over the entire lifetime of my roof?

Due to normal wear and tear, some degradation of roof reflectivity can be expected, particularly within the first few years after installation. Flat roofs may accumulate more dirt and debris because their slope is not great enough to allow washing by rain. Following maintenance procedures minimizes degradation and maximizes energy savings. Consult your roofing contractor or product manufacturer to learn more about recommended maintenance procedures and schedules.

How do ENERGY STAR qualified roof products compare with standard roof products in terms of durability?

ENERGY STAR understands that the water tightness, durability, and longevity of a roof are the primary concerns of building and homeowners. These participating manufacturers must back their compliant roof products with warranties that are comparable to their other roof products.