For Home and Building Owners

A building with a cool roof and/or walls can significantly reduce a building’s cooling costs by lowering the need for air conditioning, especially in warmer climates. The average energy savings for a cool roof range between 7% to 15% of total cooling costs. A cool roof can also help prolong the life of an air conditioning system by reducing the strain on the system during hotter times of the day and year.

For air-conditioned buildings, cool exterior walls can reduce annual HVAC energy use in single family homes between 3% and 25%, medium offices between 0.5% and 3.7%, and stand-alone retail stores up to 9% (California Energy Commission).

A cool roof and wall decrease a building’s air conditioning use by reducing the amount of heat that enters into the building. In urban areas, the combination of many cool roofs can also help reduce air conditioning use by reflecting solar radiation away from buildings, which helps lower the surrounding outdoor air temperature. Therefore, with cooler daytime temperatures, buildings and vehicles use less air conditioning, which saves energy and reduces carbon dioxide emissions from electricity-generating power plants.

For buildings without air conditioning, cool roofs and walls help the inside of the building feel cooler and more comfortable during hot months.

Since cool roofs and solar reflective-walls reduce air conditioning use during the hottest periods of the day, the associated energy savings occur when the demand for electricity is at its peak. Therefore, cool roofs and walls reduce the stress on the energy grid during hot summer months and helps avoid shortages that can cause blackouts or brownouts. In addition, building owners that pay for energy based on the time of use are able to save energy when it is at its most expensive.

Cool roofs and walls directly reduce greenhouse gas emissions by lowering the energy demand from air conditioning, which results in fewer carbon dioxide (CO2) emissions from power plants. Cool roofs and walls also cool the world independently of avoided carbon emissions by reflecting the sun’s energy back to the atmosphere, thereby mitigating global warming. A Lawrence Berkeley National Laboratory study found that world-wide reflective roofing will produce a global cooling effect equivalent to offsetting 24 gigatons of CO2 over the lifetime of the roofs. This equates to $600 billion in savings from CO2 emissions reduction (Akbari 2008).

Cities can be 1–7°F warmer during the day and 2–5°F warmer at night than in rural areas, due to heat-absorbing materials, such as dark roofs and pavements (US EPA). This phenomenon, called the urban heat island effect, creates islands of heat within urban areas where higher temperatures are sustained for longer than surrounding areas because of a lack of vegetation and darker, heat-absorbing surfaces. By immediately reflecting solar radiation back into the atmosphere and re-emitting some portion of it as infrared light, cool roofs and walls result in cooler air temperatures for the urban environment during hot summer months.

Cool roofs and walls improve air quality by slowing the formation of ground-level ozone, the main component in smog. Smog is created by photochemical reactions of air pollutants and these reactions increase at higher temperatures. Therefore, by reducing the outdoor ambient air temperature, cool roofs and walls decrease the rate of ground-level ozone that contributes to smog formation.

Lower ambient air temperatures and improved air quality also result in a reduction in heat-related and smog-related health issues, including heat stroke and asthma. Lower outdoor and indoor temperatures also help prevent heat-related deaths during heat waves. This is particularly important for cities that are experiencing an increased number of extreme heat events each year, as well as cities that lack the necessary infrastructure (e.g., air-conditioned homes, cooling centers) and/or awareness of how to behave and acclimate to extreme heat.