A case study on the impact of solar reflectance attenuation and roof cleaning on a cool roof return on investment

Research has shown roofing systems with high solar reflectance and thermal emissivity lead to less heat absorption, a consequential reduction in cooling load demand, and a resultant reduction on energy expenditure. Studies on energy savings from cool roof coatings have been conducted for decades and when compared to more traditional roofing systems have demonstrated energy savings ranging from 2-40%, with average savings estimated at 20%. The 20% average is widely used by cool roof industry professionals, designers, and contractors to market and sell the technology in the commercial sector to owners and owner representatives researching new roofs. While the 20% energy savings is a documented average, unfortunately there is no average roof. Each roof is unique considering size, materials, and location to name a few. In addition, the ability of the cool roof to maintain the original solar reflectance is integral to realizing energy savings. The case study calculated project payback for a 20-year cool roof design using both 30% and 20% estimated annual energy savings. In addition, building material specifications and solar reflectance attenuation in respect to reductions in cooling energy were projected into the payback calculations. Lastly, the cost impact of cleaning maintenance was added to the calculations to provide an analysis on affect to anticipated payback schedules. The results showed cleaning costs only added 1 year to project paybacks and saved over 262,244 kWh over 20 years.