Overhead savings

The solution to urban heat island effects may well be over peoples' heads, I would say.
That is to say, their roofs.
Good candidates for lowering temperatures and energy costs in the built environment of towns and cities come in the form of flat roof structures, such as schools, big box superstores and traditional urban buildings like those found in downtown Hillsville and Galax and the core of larger cities across the country and the world.
Black tar roofs — sealed to keep out water leaks — also absorb the heat from the sun's rays and can at times make the roof temperature almost boiling hot.
A cost effective solution, for both new construction and roof replacement, is to choose the "cool roof" option.
What it amounts to is creating a more reflective, i.e. white, roof surface with the goal of cutting down solar heat gain.
The Environmental Protection Agency says while the reflective roofing systems costs about the same, they can lower energy usage in a building by about 10 percent.
Right here in Virginia, an Energy Star roof replacement project at Jefferson Houston Elementary School in Alexandria showed the electricity saving possibilities.
When replacing the roof on the school built in 1970, administrators realized that a reflective roof could cut down on cooling costs, especially as the mercury in summer typically rises to 100 degrees in the eastern Virginia locality.
The old surface on the 83,000-square-foot facility was replaced in the 1990s with — to use the jargon — a white ethylene propylene single-ply membrane as part of a more insulated and reflective roofing system.
"The reflectivity of the new roof, compared with the old roof, increased from less than 20 percent to 78 percent," said the case study.
The insulation value of the roofing was doubled at the same time to stop the heat gathered at the surface from raising the temperature inside the school.
While the cost of the cool roof was "no higher," the school started seeing immediate savings after the installation was finished.
The total cost of the replacement came to $330,000, or about $3.87 per square foot, the EPA said. The electricity costs for the year fell by $31,000, or 37 cents per square foot.
Electricity savings totaled a whopping 514,000 kilowatts for that one elementary school for the year.
That's a reduction of more than 1.2 million tons in carbon dioxide emissions, equal to taking about 122 cars off the roads, according to the EPA information.
"These savings are due to both greatly reduced electric power demand and lower electric energy consumption," the case study said.
On top of that, the school saw these electricity use reductions despite adding to the square footage of the facility by enclosing an interior courtyard and turning it into classrooms.
"The white EP membrane accounted for approximately 30 percent of the realized savings," said the EPA. "Based on their energy-saving potential and ease of installation, white, reflective, single-ply membrane materials have become the roofing product of choice for Alexandria City Public Schools."
With that good introduction to energy efficiency as a starting point, the school also received further upgrades to lights and air conditioning and heating systems and a new energy management system, the EPA added. These improvements combined with the new roof cut the school's electricity usage by a total of half.
Sunny California has long known the benefits of reflective roofs, seeing the systems as not only relief from the heat but as a way to stretch the available power supply and prevent electricity shortages in the summertime, according to a California Energy Commission news release dating back to 2002.
Peak temperatures can range from 150 to 190 degrees at the surface of a traditional roof, but the temperature on a cool roof can be on average 50 to 60 degrees lower.
Other benefits touted by the CEC include: extended life of air conditioning units due to less cycling and operations; improved comfort for workers in buildings and on the roof; and reduced air temperatures surrounding the cool building, lessening the heat island effect.
So, it seems there are considerable opportunities to save on overhead electricity costs and some continuing maintenance simply by installing a white tinted roof.
As building continues and as rooftop surfaces in cities expand, the benefits to installing cool roofs should accrue.
The Heat Island Group, at http://eande.lbl.gov/HeatIsland/CoolRoofs/, conducted a study in 11 cities to estimate the net savings by using the reflective roofs, for example.
Considering both summer cooling savings and increasing needs for heating in winter, this study still found the Windy City of Chicago with its winter chill saw decreased power costs in the seven figure range.
Hot spots savings were considerably more, of course. The study calculated the impact of white roofs in Los Angeles to total $35 million a year, $37 million in Phoenix, $27 million in Houston and $20 million in Miami and Fort Lauderdale.
Heat Island Group took these findings and expanded them to forecast nationwide savings, which the researchers said came to $750 million worth of energy reductions a year.
All this means that there's abundant acreage overhead that could be tapped to lessen the impact of our buildings on the environment.