Белая краска на крыше школы в Флориде снизила энергопотребление кондиционеров на 35%

The school's roof was unremarkable at the start: an unexceptional 10,000-square-foot roof of gray modified bitumen over a plywood substrate, with a solar reflectance of only 23%, according to the Florida Solar Energy Center's baseline monitoring. Researchers on the 'Demonstration of Cooling Savings of Light Colored Roof Surfacing in Florida Commercial Buildings' project monitored the school's thermal performance for a full year before and after the roof was coated, tracking roof and ceiling temperatures, weather conditions, and the electricity use of the chiller and air handlers. The initial year was crucial for the research. Without that year of data, there wouldn't be a way to distinguish between the effect produced by the roof coating and any particular mild summer season. What changed once the roof turned white The roof coating using an acrylic white elastomeric finish was done in May 1995. In just three coats, reflectance increased to 68%, while after a year, in spite of weathering and dirt accumulation, it remained at 63%. This appeared to have an immediate effect on the chiller's performance. When comparing the same summer weekday hours across the two years, the chiller's electrical demand during the 3-4 p.m. EST peak window fell by 35%, dropping from 16.2 kW to 10.6 kW, according to the Florida Solar Energy Center's report on the monitoring project. On an annual basis, the chiller's energy usage has been reduced on average by 10%, which equals 13,000 kWh in annual savings. The 10% reduction in chiller energy usage is notable on its own, and the 35% reduction in peak-hour demand is also significant for utilities because peak demand can drive infrastructure costs and higher rates. Why the findings extend well beyond one school While results from a single building, regardless of the quality of the data, do not imply results in the real world at scale, a different body of work by Ronnen Levinson and Hashem Akbari at Lawrence Berkeley National Laboratory’s Heat Island Group is highly informative in this respect. Their 2010 paper, ‘Potential Benefits of Cool Roofs on Commercial Buildings: Conserving Energy, Saving Money, and Reducing Emission of Greenhouse Gases and Air Pollutants’, published in the journal Energy Efficiency, simulated the effect of converting 80% of U.S. commercial roof area to white, high‑reflectance roofs. Form of climate engineering. Image credits: Wikimedia Commons The outcome of their analysis was a potential reduction in cooling site energy use of 10.4 terawatt‑hours annually (about 37 petajoules), along with energy cost savings of almost $735 million. The study estimated that these net savings held despite the winter heating penalty associated with reflective roofs, since in most states the summer savings were estimated to exceed the penalty. Together, the two studies suggest a pattern: an individual Florida school demonstrated double-digit percentage reductions in chiller energy consumption, while the nationwide model, based on the same principles, points to projected savings in the hundreds of millions of dollars. The trade-offs a reflective roof still brings However, all this does not imply that whitening is a solution for every situation. According to the U.S. Environmental Protection Agency, cool roofs can increase heating expenses in colder regions because, along with reflecting excess summer heat, they also reflect winter sunlight that might otherwise help warm the building, a ‘wintertime heating penalty’ noted in EPA’s 'Reducing Urban Heat Islands: Compendium of Strategies'. Reflectivity is also not a permanent property: coatings lose reflectance as dirt, fungal growth, and other environmental factors accumulate, apparently the case in Cocoa Beach, where reflectivity dropped from 68% to 63% after one year, according to the Florida Solar Energy Center’s Our Savior’s School report. Climate and construction type matter as well. The savings at Our Savior’s Elementary School likely reflect Florida’s long cooling season and heavy air‑conditioning use, as noted in the Florida Solar Energy Center’s (FSEC) report on the project. What the data actually supports However, these data do not support the view that painting a roof white can replace insulation, energy‑efficient equipment, or effective building‑envelope design; rather, cool roofs function best as a complement to those measures. Instead, both the individual case study and the nationwide model suggest a relatively inexpensive, low‑tech option that can reduce cooling load and tends to work best in sunny, hot areas with high air‑conditioning demand. (Catch all the US News, UK News, Canada News, International Breaking News Events, and Latest News Updates on The Economic Times.) Download The Economic Times News App to get Daily International News Updates. (Catch all the US News, UK News, Canada News, International Breaking News Events, and Latest News Updates on The Economic Times.) Download The Economic Times News App to get Daily International News Updates.