Article Title: Cool Roof Product Guides

Excerpt: Reflective Roofing Materials There are four broad categories of roofing materials that can be used to upgrade a roof's reflectivity to ENERGY STAR levels of efficiency: metal, tile, roofing membranes and reflective coatings.

Excerpt: Metal Roofs are durable, fire retardant and almost maintenance-free. They reflects heat and block its transfer into the building's top floor. Research by the Florida Solar Energy Center in 1985 showed that metal absorbed 34% less heat than asphalt shingles, and homeowners switching to metal roofing reported saving up to 20% on their energy bills. The one drawback to metal roofs is that they have a low emittance, which means they trap solar radiation and don't emit the heat. Metal roofs typically have solar reflectance values between 0.50 and 0.70 but their overall efficiency is reduced by their low emittance levels. They perform better when combined with a polymeric coating that helps to offset the low emittance of the metal. These coatings, which are similar to paint, can be factory-applied.

Excerpt: Roofing Tiles can be ceramic or fabricated from cement concrete. Some of the lighter-weight types contain fibers (e.g., cellulose) for added strength. The color of a tile may be applied as a coating or dispersed throughout. Perhaps the most common type of roof tile is the Spanish-style red barrel tile made from fired clay. The modern version of this tile is sometimes a cement tile with a suitable coating. They can have respectable reflectance ratings if they are of a light color. They also have enhanced air circulation compared to other roofing types, because ambient air can circulate below as well as above the tile. Enhanced air circulation helps the roof shed solar heat more readily. Solar reflectance levels for tiles range from a low of 0.18 for red concrete tile to a high of 0.74 for white concrete tile. Tile is more appropriate for steeper-sloping roofs.

Excerpt: Roofing Membranes are fabricated from strong, flexible waterproof materials. They may be applied in multiple layers, as in the venerable built-up roof (BUR), or they may consist of a single-ply membrane. Membranes usually contain a fabric made from felt, fiberglass or polyester for strength, which is laminated to or impregnated with a flexible polymeric material. The polymeric material may be asphalt, synthetic rubber known as EPDM, or synthetic polymers such as PVC. The color of the polymer ranges from black to white, often depending on the amount of carbon present. The upper surface of the membrane may be coated with a pigmented material which determines the color and solar reflectance, or it may simply be ballasted with roofing gravel. When a dark membrane is surfaced with roofing granules, the membrane has the appearance (and solar reflectance) of asphalt shingles and is less effective in reducing cooling loads. Roofing membranes generally have high reflectance and emittance levels (above 0.60), as long as it is of a light color.

Excerpt: White Reflective Coatings contain transparent polymeric materials, such as acrylic, and a white pigment, such as titantium dioxide (rutile), to make them opaque and reflective. These coatings typically reflect 70 to 80% of the sun's energy. Despite the white appearance, these pigments strongly absorb the 5% or so of the sun's energy that falls in the ultraviolet (UV). Thus, the pigments help protect the polymer material and the substrate underneath from UV damage. As long as the coating is white or light-colored, the roof will have high reflectance and emittance levels.

Article Title: Roofing Comparison Calculator

Excerpt: This calculator helps you estimate how much energy and money you can save by installing an ENERGY STAR® labeled roof product on your home or building.

Excerpt: The building should be an air-conditioned residence (assumed to have a roof with 20% slope), office, or retail/commercial building. No savings are available for a building that is not air conditioned, although a reflective roof can make it cooler.

Excerpt: The calculator asks you to supply the equivalent flat roof area. If you are calculating the savings for a building with a sloped roof you should specify the area of the floor space covered by the roof. For multi-story building give the square footage under the roof (usually the top story).

Excerpt: This calculator calculates net savings for buildings, balancing cooling savings with minor increases in heating costs. The calculator works for buildings heated by gas or an electric heat pump.

Excerpt: To correctly calculate cooling savings and heating costs, this calculator takes into account the amount of insulation in your roof. Savings from cool roofs are largest for lightly insulated roofs.

Article Title: What Can Be Done - Cool Roofs

Excerpt: Cool roof materials have two important surface properties: a high solar reflectance and a high thermal emittance. Solar reflectance is the percentage of solar energy that is reflected by a surface. Thermal emittance is defined as the percentage of energy a material can radiate away after it is absorbed.

Excerpt: Solar reflectance and thermal emittance have noticeable effects on temperature. Conventional roof surfaces have low reflectance (0.05 to 0.25) and high thermal emittance (typically over 80%) and heat up to 150 to 190°F (66 to 88°C) at midday during the summer. Bare metal or metallic surfaced roofs have high solar reflectance (0.5 or higher) and may have low thermal emittance (20 to 60%, depending on their surface treatment) and warm to 140 to 170°F (60 to 77°C). Cool roofs with both high reflectance and high emittance warm to only 100 to 120°F (38 to 49°C) in the summer sun.

Article Title: PG&E Offers the Coolest 'Cool Roof' Rebates to Homeowners: Financial News - Yahoo! Finance

Excerpt: "Cool Roofs" are made from highly reflective material that keeps roof surface temperatures relatively cool in the hot sun, which reduces attic temperatures, which reduces ceiling surface temperature, which means homeowners don't need to use the air conditioner as much. Reduced AC usage means lower energy bills.

PG&E customers who purchase a "Cool Roof" will not only get a rebate, they will see immediate energy savings. On average, customers with cool roofs reduce their air conditioning usage by an average of 10 to 20 percent, which will reduce their electric bill by 5 to 10 percent during the warm summer months.