Two research engineers are claiming to have developed prototypes of energy-efficient roofs and attics.
These `Green' roofs could keep you warm in winter and cool in summer.
"From seasonal simulations that I've been able to do, it could mean up to an eight percent reduction on a cooling bill," said research engineer William Miller.
Miller and another research engineer Jan Kosny developed the technology at Oak Ridge National Laboratory in Tennessee.
While on the surface 8 percent might not seem like a huge number, if just half of the homeowners in the United States installed the new roof system, they could save 100 trillion BTUs of energy combined - the equivalent of more than 800 million gallons of gas.
According to Miller, the prototype system combines four different technologies into one high-efficiency roof: pigments that reflect infrared light, barrel-shaped tiles (instead of shingles), radiant barriers, and phase-changing materials.
The radiant barriers are thin layers of metal or aluminium foil that help limit the amount of heat that transfers into the attic.
In the current design, those barriers sandwich the fourth technology: a layer of phase-changing material. This is made up of tiny beads of wax with interiors designed to melt at particular temperatures.
During the day, the beads absorb heat from the sun and melt. At night, as the surrounding air cools, the beads give off the heat and solidify.
The neat part is that it uses standard materials already available to contractors, but getting people to adopt a new kind of roof could be a challenge.
"It's a very simple process but the politics and the realism of it is the most difficult part," he said.
Miller and Kosny found that the roof system helped reduce attic temperature by 22 degrees Fahrenheit during a typical summer afternoon.