Quality First Home Improvement Newsletter
Sept 2009 - Issue 102
In some areas on a hot summer day, the temperature of the roof of a house can climb above 160°F. The hot roof radiates heat across the attic air space to the insulation below. As the temperature of the insulation increases, more heat is conducted through the ceiling into the home. This results in higher cooling bills for the homeowner.
Insulation and good attic ventilation are necessary to keep your home cooler in the summer. However, these are topics for another day. Today, let's discuss the main source of the transferred heat, your roof.
Emissivity and Reflectivity
These are the two factors that contribute to the amount of heat your roof absorbs and reflects. According to Energy Star, "The emissivity 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 have poor emittance values, averaging around 0.85 (85%)." The higher number means it has low emissivity, or the inability to released heat efficiently.
Solar reflectance is the most important characteristic of a roof product in terms of yielding the highest energy savings during warmer months. Scientists use a number between 0 and 1, or 0% and 100%, to express reflectivity. 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.
Note: Currently emissivity is not a requirement for an Energy Star rating on a roof. However, the EPA posts 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.
Types of Cool Roofs
Energy Star roofs, also known as "cool roofs" are now available to home owners. Today cool roofs are manufactured from nearly all types of roofing materials. These include asphalt roofing, metal, cement, and clay tiles. There are reflective coatings that can be applied to certain roofs that may qualify for local utility company rebate programs, but these are not eligible any Federal tax credits.
Asphalt Cool Roofs
New advancements in solar reflective materials being used on asphalt shingles are making the roofing material even more attractive. Energy Star rated asphalt shingles are readily available. They are only available in light colors, white being the most reflective. Besides lowering energy costs, asphalt "cool roofs" will last much longer than a standard asphalt roof, as they reflect more of the damaging effects of the sun's heat and UV radiation. Energy Star asphalt roofs qualify for a Federal tax credit of 30% of the cost of materials, up to $1500. Some local utility companies may offer a rebate as well. Check with your local utility company.
Metal Roofing
Metal roofing has come a long ways since the days of corrugated roofing and its problems with rust and corrosion. Today metal roofing is made from steel, and can be found in numerous designs such as tiles that simulate wood or slate, color tiles, and Spanish tile designs.
Cool roof metal tiles are very reflective, and come in an array of colors. Energy Star metal roofs qualify for a Federal tax credit of 30% of the cost of materials, up to $1500. Some local utility companies may offer a rebate as well. Check with your local utility company.
Cement and Clay Tiles
These types of roofs have excellent reflective, and emissivity characteristics. They come in wide variety of colors and designs. Standard tiles are heavy in weight, however, there is a good selection of light weight designs available. Tile roofs are more costly than other types of roofing material, but a properly installed tile roof is beautiful, very durable, and both standard and newer "cool roof tiles" will definitely help you cut costs on summer cooling bills. It is unfortunate that the Federal government has not created a tax incentive for purchasing these types of roofs. Doesn't make any sense to me. Fortunately, many local utility companies are offering a rebate. Check with your local utility company to see what they offer.
Clean Green
Even if you select a cool roof product that doesn't qualify for the Federal tax rebate, you will still save energy, help lower the carbon footprint, and help to create a greener environment.
Quality First Home Improvements Inc offers cool roofs in a wide range designs and styles.
More News Articles
Author - Roland G. Ludlow