DOE Awards $224,000 to PPG to Develop New Class of Pigments for Cool Coatings

PPG Industries’ industrial coatings business, Pittsburgh, has received a $224,000 award from the U.S. Department of Energy (DOE) to help to develop dark-colored pigments for cool metal roof and façade coatings that incorporate near-infrared (NIR) fluorescence and reflectance to improve energy performance.

The award is part of a $530,000 project that includes a $250,000 award to the Lawrence Berkeley National Laboratory (Berkeley Lab) to partner with PPG on the research and $56,000 in cost-sharing by PPG.

According to PPG, while painting a metal roof white is the simplest way to keep the sun’s energy from heating a building’s interior, it usually is done only if the roof is flat. For sloped roofs, darker coatings that absorb more visible light are preferred, including many that also absorb more invisible NIR solar radiation. Because colors absorb more solar energy as they get darker, buildings with dark-colored roofs are warmer and more expensive to cool than buildings with white roofs.

To combat this problem, PPG makes products such as ULTRA-COOL® coatings that reflect invisible NIR radiation, but dark ULTRA-Cool coatings still absorb visible light energy that ultimately is converted into heat.

The goal of the PPG/Berkeley Lab program is to develop a more advanced class of dark-colored pigments that can convert a portion of the absorbed visible light energy into NIR energy that is radiated away from buildings.

The new pigment technology under investigation would be an advance over current cool-coating pigments, PPG and Berkeley Lab say, estimating that cool coatings based on the new pigment technology could achieve effective solar reflectance (ESR) values of 0.5 to 0.7 compared to ESR values of 0.1 to 0.3 for standard pigments. An ESR improvement of 0.4 and widespread deployment of coatings with these pigments for residential applications in warm and hot areas of the U.S. could save up to $1.3 billion annually in related energy costs.

PPG recently partnered with Berkeley Lab’s Heat Island Group to study the effects of dirt build-up on cool roof coatings and with Berkeley Lab’s Windows & Daylighting group to examine energy-efficient window designs.