How would you like to come home on a hot summer day and not run to your AC thermostat because you can barely breath in the stifling heat? You may not be aware of it, but the high temperature inside is in great part caused by the dark colored roof of your home or office. This happens because the dark color of the roof attracts the sun and traps this heat inside the house instead of reflecting it back into the atmosphere, in a much the same way as dark clothing makes us more sweaty and hot during the summer. Such heat is particularly an issue and even a health hazard for the elderly and children, especially if they are not able to afford high cooling costs in the summer. If instead you would like your house to be a comfortable 80 degrees F when it is 100 degrees outside, a white color roof is the perfect solution.
What is a white roof?
Dark roofs are typically made of asphalt, tar and modified bitumen, or asphalt-based roofing shingles. These roofing materials absorb as much as 90 percent of the sun’s heat energy. On the contrary, white roofs, which can be made from different types of roofing materials, deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun), and high thermal emittance (the ability to radiate absorbed, or non-reflected solar energy). As a result, a white roof can absorb as little as 10 percent or 15 percent of the sun’s heat.
Benefits of a white roof
In terms of energy savings for your home, if you use a white roof and you have air conditioning, depending on the geometry of the building, you can save as much as 15% on energy bills by just simply having a white roof. Because white roofs reduce the use of air-conditioning during the day’s hottest periods, the energy savings occur when electricity demand is at its peak. Consequently, if you are a home or building owner and pay for your energy based on the time of use, you save energy when it is at its most
In case you are not ready to replace your old dark roof with a new white roof, but still want the benefits of a white roof, consider installing a white roof coating. There are a number of coatings that will substantially improve an existing roof’s reflectance. Additionally, coatings protect and seal, potentially extending the life of your roof. The installed cost of coating a roof is about $0.50 to $1 per square foot. You will definitely see a return on your investment with lower energy bills and the extended life of your roof.
From a more global perspective of helping combat global warming, white roofs and white colored pavements also change the reflectivity or the so called obidal of the earth. The sun comes in and its reflected back into space. There is no green house cap on this. The department of energy has calculated that if you replace all the building roofs today with white roofs and you go to cement style pavement instead of black tops, it would create a reflection of sunlight back into space that would be the equivalent of taking off all the automobiles in the world for 11 years!
If that is not convincing enough, research by the California Department of Energy has found that turning all of the world’s roofs “light” over the next 20 years could save the equivalent of 24 billion metric tons in carbon dioxide emissions. This number is equivalent to what the entire world emits in one year.
White Flat Roofing materials
Most common types of cool white flat roofing materials are PVC and TPO roofing membranes, and to a lesser degree White EPDM (rubber roof) membrane, and white roof coatings (Urethane, Acrylic, etc.).
All of these white roofs are “cool” naturally, because they are white, and reflect a lot more sun light vs black or dark-colored roofs. However, among these white roofs, some actually have COOL Roof label – that is US Department of Energy and other rating agencies and organization consider them to be COOL roofs, which means they meet the criteria for reflectivity and emissivity, and have special reflective pigment in the top coating.
PVC flat roofing membranes offer the longest life-cycle out of the above flat roofing materials. With its hot-air welded seams, a PVC roof can withstand ponding water, and all roof penetrations are flashed with special pre-fabricated roof flashing components. PVC roofs have been installed in US for over 35 years with very impressive track record (except for Trocal PVC roof fiasco which was exclusive to that particular manufacturer).
TPO Roofing are similar to PVC roofs in the way they are installed (also use hot-are seam welding method), but is a much newer system and have spotty track record with many reports of multiple roof manufacturers changing the formulation of their product.
White EPDM roofing is the same ad traditional BLACK rubber roofs, but have white pigment (either throughout the membrane or just top layer). White EPDM roofing has same inherited “problems” of traditional rubber roofs, in that all seams and flashing is sealed with adhesives (chemicals), which fail over time, causing roof leaks. Read more on rubber roofing problems
Government support for White roofs
White roofs have been championed by the US Department of Energy since the 80’s and the trend is slowly catching on. Large corporations such as Wal-Mart have taken advantage of the benefits of white roofs, as more than 75 percent of its outlets in the United States have white roofs. To rein in soaring energy costs, states like California, Florida and Georgia all have adopted building codes that encourage white-roof installation for commercial buildings. Moreover, many state energy offices often offer special financing for white roofs, drawing on federal funds allocated for energy-efficiency projects and green architectural design.
The best part is that if you are educated about white roofs and their benefits and are ready to make the switch, the cost of white vs black roofs is about the same. This is something very simple and something we can start doing immediately to save on our energy bills, improve our health, and help save our planet one white roof at a time.