Juliette in CA asked:
I have a modified bitumen roof. In 2011 Karnak #97 AF Fibered aluminum roof coating was applied. It is no longer effective in controlling the temperature in the house. We just received a quote to use Tropical 921 refex white elastomeric coating. My question is . . .will the Tropical 921 be as effective in controlling the temperature as the Karnak was? Or, would you recommend something else.
Hi Juliette, I do not know what part of California you live in – but choosing the right coating does require a consideration of the weather that is typical for where you live as well as a consideration on which coating might provide the best reflectivity and help keep the roof system cooler. I say this because if you are in an area of California where temperatures changes between cold in the winter and warm in the summer, the roof is being “temperature cycled” all the time and that is stressful on a roof system – as well as the coating system over it. Your current coating (Karnak #97 AF fibred aluminum roof coating) appears to have held up for 13 years so far, and that speaks well of the coating’s performance in your climate zone. Most coatings like aluminum and acrylic begin to degrade by about 10 years of life and start to show signs of their aging – many times in a decrease of reflectivity ability. While both of the coatings you mentioned are generally good coatings, the actual reflectivity of each coating is different – at least when first applied.