Adhesion of cool roof coatings to mudbrick and corrugated metal roofs: manual peel adhesion testing

Cool roof coatings are a potential climate change adaptation technique to reduce indoor temperature and energy needs. Little is known, however, on how cool roof coatings adhere to mudbrick and corrugated metal sheets, roofing substrates that are common in climate hotspots such as the African Sahel. To determine adhesion, we used manual peeling tests of cool roof coatings on mudbrick and corrugated metal sheets using heat chambers conditioned to 40 °C, and heat/humidity chambers conditioned to 35 °C with 90 % humidity. We found that cool roof coatings showed no blistering or delamination when exposed to heat and humidity. Adhesion of product to substrate was strong for the corrugated metal, even when rusted (manual peel test, level 3), and minimal on the mudbrick samples (manual peel test, level 1). Application of a primer resin consolidated the powdery mudbrick substrate, improving ease of cool roof coating application and slightly improving adhesion. We recommend three modifications to increase longevity of cool roof coatings to the mudbrick roofs: (i) extending the cool roof coating over the lip of the roof onto the wall, (ii) using fiberglass reinforcement or mechanical fixation on the edges, and (iii) using a primer resin to consolidate the powdery mudbrick prior to application of the cool roof coating.