Solar Reflectance and Thermal Emittance
Did you know that one-sixth of the electricity produced annually in the United States goes to air conditioning buildings? It’s amazing how inefficient roofing can cause your heating and cooling costs to soar. A building’s roof can heat up to 150 degrees on an average day in the summer allowing heat absorption inside the building making it almost impossible to adequately cool the interior.
So how can we make a roof cooler and stop wasting money on cooling and heating?
Many times a pre-existing roof can be prepared to reduce heat transfer and save 20-70% in annual energy costs as well as qualify for tax incentives. Regardless of the type of roof material you have. looking at the solar reflectance and thermal emittance will help you determine how to manage your building’s roof.
Solar reflectance measures the roofs ability to reflect sunlight on a scale of 1 to 10. Ability to reflect sunlight includes visible, infrared, and ultraviolet wave lengths reflected from the roof surface.
Thermal emittance measures the heat radiated away from the roof surface once it has been absorbed by the roof and then released. The absorbed heat release is also measured on a scale of 1 to 10.
- Asphalt roof surfaces with low solar reflectance (5 – 25%) and high thermal emittance (over 80%) can reach 150 -190 degrees in the summer sun.
- Metal roofs have a higher solar reflectance (50% and higher) and low thermal emittance (2 – 66%) and can reach 140 -170 degrees
- Cool roofs have higher solar reflectance and high thermal emittance and only measure 100 to 120 degrees in the hot summer sun.
Once you have determined your roofs reflectance and emittance you can access what type of roof repair or roof replacement is needed.
If you have questions about your large roof or commercial building, call Pat Kohls of Kohls Foam Systems at 612-708-4111. An expert with decades of experience with flat and low slope roofs, Pat can help you determine if your roof just needs minor repairs or energy-saving insulation, or if you should repair the entire roof with an energy efficient cool roof coating.
