Staying Cool
Jun 1, 2001 12:00 PM, By Mike Kennedy
For a school or any other facility, the most important function of a roof is to keep out the elements—wind, moisture and leaks that could damage a building’s infrastructure and the property inside.
But once that basic need has been met, school officials should consider other characteristics of roofing materials that could enhance a building’s value and improve an institution’s bottom line.
Roofs can make the buildings they protect susceptible to significant heat gain because of their prolonged exposure to the sun. That exposure can weaken roofing materials and lessen the life expectancy of a roof, and it can increase the burden placed on a building’s cooling system.
In recent years, schools and universities constructing new facilities or renovating old ones have been turning to roofs that use insulation, reflective materials and lighter colors to ward off heat and keep buildings cooler with less reliance on climate control.
"We haven’t found a down side," says Tim Nelson, director of maintenance and operations for the Antioch (Calif.) Unified School District, which has installed several energy-efficient roofs on its schools.
The white choice
In Alexandria, Va., temperatures can climb to 100 degrees in the summer. The Jefferson Houston Elementary School, with little or no insulation and an electrical heating and cooling system, was one of the worst energy guzzlers of all the buildings in the Alexandria City Public Schools system.
"The electric heating units on the roof were like toaster ovens in the summer," says Mark Krause, supervisor of design and construction for the district.
So in 1994, when it was time to replace the roof of the 83,000-square-foot, one-story building, Krause knew that the right material could make a noticeable dent in the school’s utility bill.
"One of the primary goals was to reduce the energy cost," says Krause.
Krause chose to install a white polymer roof that provided more insulation and reflected more of the sun’s rays away from the building. Another factor in the decision: the material could be heat-welded in place, which Krause found was a more reliable seal than having the roof glued into place.
"The heat-welded option was what convinced us to go with the (white) roof," says Krause.
The reflectivity of Jefferson Houston’s roof increased from less than 20 percent to 78 percent, and the insulation value increased from R-10 to R-20. That translated into dramatic savings: Energy costs dropped to $90,000 a year from $120,000 a year, even though the school had added classrooms that increased the energy load.
"A couple of years after that, we changed the rooftop HVAC systems and were able to replace them with units that have smaller compressors," says Krause.
That helped the school slash costs even more. By 1997, energy costs at the school were $60,000 a year.
Buoyed by that success, Alexandria has installed white reflective roofs on several of its schools. "We are doing two more buildings this summer," says Krause.
Reflective coatings
Schools can improve the energy efficiency of their roofs without having to install an entirely new roof. Reflective coatings, applied like paint, can repel heat that a building would otherwise absorb.
In 1994, the Florida Solar Energy Center asked officials at Our Savior’s Elementary School in Cocoa Beach, Fla., to take part in a study on the effect of reflective roofing surfaces on energy consumption.
The 10,000-square-foot building had a gray modified bitumen roof over plywood decking. The Center collected energy data for a year, and then applied an acrylic white elastomeric coating on the roof in May 1995.
Roof and classroom temperatures were significantly lower after the coating was applied. "Chiller electrical power was reduced by an average of 10 percent," the center’s report says. During summer weekdays, when electric power rates were highest, the peak electric power demand had fallen by 35 percent.
"The school staff noted that interior comfort conditions were noticeably improved by the white roofing system," the report says. "Reflective roofing shows considerable promise for peak demand and energy savings in Florida’s school buildings."
In Antioch, Calif., the school district has used both foam roofing and reflective coatings to improve energy efficiency as it upgrades its roofs. The differences can be measured in years: Foam roofs can be sprayed over old roofs and form a watertight seal "that will last for 30 years," says Nelson. Reflective coatings can be applied to existing structures and extend the life of the roof by as much as 10 years.
But the difference a reflective roof makes also can be measured any hot summer afternoon.
Sidebar: Be careful up there
Reflective roofs can bring welcome coolness and cost savings to schools, but officials say there can be some pitfalls.
In Alexandria (Va.) City Schools, Mark Krause, supervisor of design and construction, says the roofs can be susceptible to damage from workers who must get on the roofs to maintain equipment.
"A lot of them weren’t very careful about where they dropped their tool chests and damaged the roofs," says Krause.
To solve the problem, the district installed four-foot-wide protective walk pads around heating and cooling units on school roofs.
Tim Nelson, director of maintenance and operations for the Antioch (Calif.) Unified School District, notes that many people who deal with roof installation think foam roofs are "scary," but the best way to safeguard against trouble is to ensure the installers know what they are doing.
"It’s critical that the foam is properly applied, with well-written specifications," says Nelson. "If it’s not properly applied, it’s not going to last."
Acceptable Use Policy blog comments powered by Disqus
