Why Cool Roofs?

According to the Environmental Protection Agencies Energy Star website:

Americans spend about $40 billion annually to air condition buildings — one-sixth of all electricity generated in this country.

Benefits of Cool Roof products such as Elastikote™ include:

• Saves Money and Energy. According to EPA, about $40 billion is spent annually in the US to air condition buildings — one-sixth of all electricity generated in a year! Cool roof products reduce the amount of air conditioning needed in buildings, and can reduce energy bills by up to 50 percent.

• Downsizes Cooling Equipment. A reflective roof can reduce peak cooling demand by 10-15%. As a result, the home or building owner may be able to purchase a smaller, more efficient, and less expensive cooling system.

• Green Roof Ready. Over the last decade, green roofs have become a more common feature in urban environment. At the heart of any green roof is a roofing membrane; Elastikote's™ unique properties make it an excellent choice for this role. Read more about Green Roof Components.

• Decreases Pollution in Urban Areas. Reduced energy demand means less burning of fossil fuels, which results in less pollution from power plants. Also, cool roof products help to reduce the “heat island effect,” in which dark, heat-absorbing buildings and paved areas make the air in urban areas hotter, and more smoggy. Read more about Urban Heat Islands.

• Resists Thermal Shock. Cool roof products maintain a more constant temperature and reduce thermal shock, which occurs when cool rain hits a hot roof, causing a sharp drop in temperature. During temperature changes, a roof expands and contracts, causing stress and degrading the roof. Read more about Thermal Shock.

• Protects Against Water Pooling Damage. The collection of water on a roofing deck can cause structural failure not only due to the weight of the water, but also due to penetration of the deck by the water. The freeze/thaw cycle exacerbates the problem. Elastikote™ has extremely low permeability, which reduces the risk of deck damage due to water permeation.

Reflectance and Emittance

A high solar reflectance - or albedo - is the most important characteristic of a cool roof as it helps to reflect sunlight and heat away from a building, reducing roof temperatures.

-- EPA Reducing Urban Heat Islands: Compendium of Strategies

A high thermal emittance also plays a role, particularly in climates that are warm and sunny. Together, these properties help roofs to absorb less heat and stay up to 50-60°F (28-33°C) cooler than conventional materials during peak summer weather.¹

Building owners and roofing contractors have used cool roofing products for more than 20 years on commercial, industrial, and residential buildings. They may be installed on low-slope roofs (such as the flat or gently sloping roofs typically found on commercial, industrial, and office buildings) or the steep-sloped roofs used in many residences and retail buildings.

Through the ENERGY STAR program, EPA and the Department of Energy (DOE) help consumers and other purchasers identify the most energy efficient roofing products.

Roofing materials with the ENERGY STAR label have met the minimum solar reflectance and reliability criteria. Based on 2006 data from more than 150 ENERGY STAR partners, shipments of cool roof products have grown to represent more than 25 percent of these manufacturers' commercial roof products and roughtly 10 percent of their residential roof products.

Source: EPA's Reducing Urban Heat Islands: Compendium of Strategies

ElastiKote™ Exceeds the Standards

Minimum Acceptable Values

* Although voluntary, many state and local authorities are requiring designers to adhere to these guidelines for specific building types, for example government funded projects.

Definition of Terms

Thermal Emisivity (emittance) is a measure of solar radiation (sun's rays) that is first absorbed and then radiated from a roof, expressed as a number between zero and one. The higher the value, the better the roof radiates heat. Any solar radiation that is not reflected (rejected outright, as with a mirror) is absorbed; this absorbed energy is then either radiated (i.e., emitted as infrared) or retained (adiabatic heat). In theory, the surface temperature of a material with 100% thermal emissivity would be equal to the ambient temperature (i.e., that of the surrounding air). Heat that is not released via the relatively efficient mode of infrared emittance is retained by the roof, which causes a buildup of heat. That heat is then released to the surrounding atmosphere via the less efficient (and slower) mode of conduction and convection.

Solar Reflectance Index (SRI) indicates the roof's ability to reject solar heat, and is essentially the combined value of reflectivity and emittance. It is defined such that a standard black is zero (reflectance 0.05, emittance 0.90) and a standard white is 100 (reflectance 0.80, emittance 0.90). Because of the way SRI is defined, very hot materials can have slightly negative SRI values, and very cool materials can have SRI values exceeding 100.

ASTM C1549 Standard Test Method for Determination of Solar Reflectance Near Ambient Temperature Using a Portable Solar Reflectometer (i.e., field testing).

Energy Star states that a "product shall be tested [for initial solar reflectance] using ASTM E 903 Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres (i.e., lab testing), but that a "product may also be tested using ASTM C 1549 (see above)¹; "maintenance of solar reflectance" is field tested in situ after three years using "either ATSM E 1918 Standard Test Method for Measuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in the Field or ASTM C 1549.²

¹ Energy Star Program Requirements, p. 02.

² Energy Star Program Requirements, p. 04.