Over the past several decades, there have been many changes to traditional low slope roofing materials and substrates. Many of these changes have been driven by environmental initiatives to reduce energy cost, lower CO2 emissions, address climate change concerns, and lower volatile organic compound (VOC) emissions.
Solar reflective roof coatings are a part of a building’s envelope, acting as a protective barrier against inclement weather, damaging UV rays and water permeation. They must also be flexible enough to withstand extreme temperature changes and resist cracking and delamination from the substrate.
These lifespan-extending coatings are popular due to their ease of application, optimum cost-to-performance balance, energy efficiency and sustainability.
“People choose solar reflective acrylic roof coatings because they’re able to reflect the heat energy of the sun,” says Dr. Sridhar Iyer, Technology Expert at BASF. “They have a huge impact on the building in terms of reducing its energy consumption while also cooling the environment around it to mitigate the heat island effect.”
The shift in substrates
One of the formidable challenges that solar reflective roof coatings encounter is the need to adhere to diverse roofing substrates that can vary substantially in the chemistry of their composition. These substrates include metal, spray polyurethane foam, asphaltic, built-up roofing (BUR) and membranes such as TPO, PVC and EPDM.
TPO membranes have been the predominant choice for low slope roofing in the past several years. They’re installed as a rolled membrane that can be either mechanically fastened to the roof or adhered with a roofing adhesive. Adhesion to TPO is a significant challenge for water-based solar reflective roof coatings due to its very low surface energy.
One approach to address this challenge is to use solvent-based primers to achieve adhesion. Because these primers present handling and environmental hazards, the industry prefers water-based alternatives.
“There’s a significant challenge in getting a water-based coating to stick to a low-energy substrate because of the two contrasting surface energies,” explains Iyer. “It's very difficult to get adequate wetting on a low-energy substrate.”
Low energy? No problem.
BASF develops water-based acrylic coating solutions with a focus on adhesion to difficult substrates, including TPO, EPDM, asphalt and smooth APP, with more planned for the future. These solutions offer strong all-around performance and a sustainable value proposition with minimal environmental impact.
“We currently offer select polymers and primers that adhere well to low-energy and HFC-free foam substrates, and we have ongoing developments to meet the challenging demands in the roof coating industry,” says Michael Guibault, Business Manager of Roof Coatings in BASF Construction Solutions.
Aside from TPO and HFC-free foam, there’s another ultra-low-energy substrate that poses an even greater adhesion challenge: silicone coatings.
Although silicone coatings are recognized for their water-repellant properties, they come with a host of problems. Its impermeable nature prevents entrapped substrate moisture from readily escaping, resulting in blisters that can deteriorate the life of the roof. Silicone coatings are also prone to tears that can cause moisture intrusion and subsequent damage to the roof.
Silicone coatings generally lose their reflectivity prematurely and tend to discolor within a relatively short period of outdoor exposure. Subsequently, building owners do not reap the energy reduction and cost savings benefits expected from such coatings. These are some of the reasons building owners wish to recoat silicone roofs, which is presently difficult to do with a simple recoat of the acrylic coating.
“Currently there is not an acrylic water-based coating solution that sticks to silicone in the market,” says Guibault. “We want to be the first. Silicone's the most difficult challenge for us, and we’re working on new product concepts designed for adhesion to silicone while addressing the aforementioned silicone coatings challenges.”
A smarter, more sustainable roof
Changing regulations and policies are one of the key drivers for innovation. New regulations are gradually phasing out HFC blowing agents used in certain polyurethane foam applications, and several states are looking at the prospects for ultra-low-VOC coatings.
BASF’s Brilliance line of water-based polymer chemistry solutions offer sustainable benefits over solvent-based solutions. They’re safer to work with, emit lower VOCs, and are easy to apply.
Initiatives such as The Cool Cities Network and Million Cool Roofs Challenge are focused on proliferating the use of solar reflective roof coatings globally to achieve sustainability goals, and they are gaining traction as the benefits of solar-reflective roof coatings become more widely known.
Down the pipeline
BASF has been recognized as an industry leader for innovations that offer features such as early rain resistance, high-build coatings in a single pass, and coatings with superior asphalt bleed resistance.
The challenge for BASF is to continuously innovate and deliver creative solutions that meet the needs of our customers. By using BASF’s global research capabilities and collaborating with external partners, new technologies and innovations are being created for the ever-changing world of roof substrates.
For more information on BASF’s water-based flexible roof coatings, Click Here.