Sherwin, John; Sonne, Jeffrey; Barkaszi, Stephen
Roofs; Cooling; Data Analysis; Buildings
Architects and designers have long known that light-colored building roofs can reduce cooling needs. Recently, monitoring studies in Florida have made an effort to quantify these savings. Experiments in existing residences have shown that a white reflective roof can reduce cooling requirements by an average of 20%. However, until now there has been no investigation in Florida's climate to examine the potential in commercial scale buildings.
To remedy this need, a two year study was performed on a private elementary school building in Cocoa Beach, Florida. Our Savior's Elementary School was monitored for an entire year in a base line condition beginning in May 1994. Detailed 15-minute data was obtained on building thermal conditions, weather and chiller and air handler electrical demand.
The 10,000 square foot facility had a gray modified bitumen roof over plywood decking with a measured solar reflectance of 23%. The dropped ceiling above the classrooms was insulated with R-19 fiberglass batts, although the insulated chilled water lines were located in the hot roof plenum space. In May, of 1995 the roof of the facility was covered with an acrylic white elastomeric coating. The measured solar reflectance after the third application was 68%; measured after one year of exposure the solar reflectance had only diminished to 63%.
Data analysis of the year pre and post the roof resurfacing revealed that the roof surface, roof plenum and classroom air temperatures were significantly lower during the second year of monitoring. In addition, chiller electric power use was reduced by an average of 10% from one year to the next, totaling 13,000 kWh in annual savings. However, peak electrical demand was much more strongly impacted than energy. Daily average annual demand reductions of 1.5 kW were observed between 9 AM and 4 PM on an annual basis. Confining the analysis to weekdays and during the summer greatly magnified observed differences (see E-1). Summer weekday utility peak coincident electrical demand of the cooling system between June and September from 3 - 4 PM EST was lowered by 5.6 kW -- a 35% reduction over the previous year. Beyond the cooling energy and demand savings, the school staff noted that interior comfort conditions were noticeably improved by the white roofing system. Based on these initial results, we conclude that reflective roofing shows considerable promise for peak demand and energy savings in Florida's school buildings.
Buildings - Cooling; Data Analysis; Buildings - Roofs
Florida Solar Energy Center and Parker, Danny, "Demonstration Of Cooling Savings Of Light Colored Roof Surfacing In Florida Commercial Buildings: Our Savior's School" (1996). FSEC Energy Research Center®. 771.