Beating the heat with a Temperature-lowering Exterior Coating System :
University of South Florida
With 246 sunny days, an average UV index of 6.9, and 74 days of 90-plus-degree temperatures a year, Tampa, Florida sees its fair share of high cooling costs for commercial and institutional buildings. Finding a way to reduce those costs was the goal of a recent dormitory refresh project at the University of South Florida (USF), where an infrared, heat-reflective, water-based coating system called TEX-COTE® COOLWALL® with Kynar® Aquatec® PVDF is helping to reduce building surface temperatures and related cooling costs.
PVDF-Based Field-Applied Coating for Metal Panels
Kynar Aquatec® PVDF resin is a tough, engineered thermoplastic polymer that promotes excellent weatherability, color retention, and abrasion resistance thanks to carbon-fluorine bonds that do not break down under exposure to the elements. It has extreme weatherability like that of Kynar 500® PVDF resin-based coatings, which have been used in factory finishes on exterior building materials for six decades. Side-by-side southern Florida weathering testing of Kynar 500® and Kynar Aquatec® based coatings over the past 24 years show similarly superlative performance with respect to color fade and chalking.
Kynar Aquatec® PVDF resin helps APV Engineered Coatings’ field-applied water-based NeverFade® Exterior Paints resist extreme UV rays, high temperatures, humidity and abrasion from salt spray, sand and other windblown particles. It also hinders mold, mildew and dirt pickup for over 20 years a much longer lifespan than the five-year lifecycle typically seen with high-performance urethanes and acrylic latex paints. In climates such as Florida’s, traditional high-performance paints break down under UV exposure, eroding over time and eventually leaving the building’s substrate bare and open to damage from the elements.
Cool Walls Reduce Energy Use
Traditionally, white paint has been used to keep the exterior of buildings cool, because white reflects much of the sun’s radiation back into the atmosphere. Dark colors, while aesthetically pleasing, have traditionally led to heat buildup.
With COOLWALL® with Kynar Aquatec® technology, buildings don’t need to be white to achieve solar reflectance benefits. For the USF dormitory, TEX-COTE® supplied shades of amber, gold, tan, and red COOLWALL® coatings that matched the color scheme used throughout campus.
After coating, surface temperature readings on the tilt-up concrete dorm coated with COLLWALL® were up to 40 degrees cooler than before being coated. Ongoing energy monitoring continues to display a reduction in cooling energy use compared to energy use before the COOLWALL® coating.
Durable Coatings Resist Fading
Heat accelerates the degradation and fading of exterior coatings, especially in hot, humid locations like Florida. COOLWALL® with Kynar Aquatec® Coatings are much more durable and fade-resistant than typical acrylic or elastomeric coatings and they undergo significantly less thermal cycling-related expansion and contraction stress. Their color, adhesion, and other physical properties also are greatly extended, thanks to use of water-based Kynar Aquatec® PVDF resin. For decades, architects have trusted the long-term, fade-resistance performance of Kynar 500® PVDF-based finishes, which are baked onto metal surfaces of exterior building products like aluminum doors and window frames in the factory. Kynar Aquatec® does not need to be baked, allowing it to provide the same long-term weathering performance in an air-dry, field-applied coating.
Kynar Aquatec® PVDF resin features incredibly strong carbon-fluorine bonds that prevent film erosion when exposed to the elements, keeping the film thickness consistent – and the coating’s IR-reflecting pigments protected – over time. These bonds allow its protective properties, including solar reflectance, dirt shedding, algae and mold/mildew resistance, color and gloss retention, and chalking and fading resistance to last significantly longer. Dirt shedding and algae/mold resistance properties are particularly important as dirty surfaces reduce solar reflectance.
Most common architectural coatings technologies degrade in the harsh Florida sun. They chalk and film erode quickly within a few years and have to be repainted every 5-7 years. The resistance to film erosion provided by Kynar Aquatec® allows the specialty heat reflective pigment technology to remain in place, helping to maintain lower surface temperatures across the coatings’ extended lifespan.
Decision-makers at USF agreed that the cost-benefit analysis of COOLWALL® with Kynar Aquatec® comes out solidly on the side of COOLWALL® for its cooling benefits and increased longevity. Five years post-application, the coating maintains great film integrity, excellent color and gloss retention and no mold or dirt buildup.