Problem Solving Forum
June 11 - June 15, 2018
How can I determine if my urban hospital building would benefit financially by installing a reflective roof coating on top of the current flat black roofing substrate?
Allen Zielnik of AMETEK Corp on
June 15, 2018:
Many factors will contribute to potential cost ben ...read more Many factors will contribute to potential cost benefits. Assuming the roof is not shaded by other buildings or objects, the ratio of the roof area to building volume is important, as the purpose of the cool roof is to limit heat penetration into a building. So this also means, are you in a hot, sunny location or a cooler temperate, less sunny location? It typically costs more to cool a building with electricity than to heat it with fossil fuels like natural gas. So if you can avoid some of the cooling cost, that's an ongoing savings if the roof area to building volume is large (penalty for high rise buildings). If in a less favorable climate where cooling costs are lower with a short summer and lower cost heating is more of the year, a cool roof may actually provide a heating penalty as you lose some solar heat load and increase fuel use. The Cool Roof Rating Council (www.coolroofs.org) has some resources to check out before speaking with certified contractors for a site evaluation.
Zenith Czora of Durotech Industries, Inc. on
June 14, 2018:
Consult with cool roof coating manufacturers.They ...read more Consult with cool roof coating manufacturers.They usually have conducted studies and collected data on how cool roof coatings provide benefits in reducing the cooling energy consumption. Some studies claimed that roof that is coated with white cool roof coating reduced the cooling energy consumption by 50%. This is because white pigments, TiO2, used in the coating has very high total solar reflectivity (TSR). From 100% sun radiation that hits on the surface, 92% being reflective back leaving 8%of the heat being absorbed. The effectiveness of a cool roof coating is dependent on its measured solar reflectance index (SRI), which is a composite measurement for surface solar reflectance and emissivity. The higher the number, the greater the reflectivity and the less heat being absorbed into the surface.But if the coating has poor dirt pick-up resistance and tends to retain dirt over time,it can lead to a significant decline in TSR, which also leads to less saving on energy consumption.