U.S. Environmental Protection Agency (EPA) has determined that nearly $40 billion is spent to air condition buildings in US, which amounts to one-sixth of the total electricity generated annually. In order to cut down these costs, EPA has come up with different roof materials and plans.
Roofing products should meet two specific conditions namely (1) They must be reflective, referring to the amount of light energy being reflected away instead of absorbing and (2) They must have high emissivity, referring to the quickness of how the absorbed energy is emitted into the atmosphere again.
By research, it has been found that light colors are effective in reduction of peak demand for cool energy in buildings. Normally, the roof system is the heavily exposed part of a building to sun and it tends to absorb energy, serving as a large heat sink. Hence based on the color of the roof and its reflective nature, the temperature rise within the roofing system can be altered. When the roof is enveloped by a white reflective material similar to a single ply membrane, plenum air space temperature lowers to 90ºF unlike 120ºF in the case of dark-colored roofs.
The building owners will be able to save between 20 and 70% of the cooling energy used in the building. These reflective roof coatings can also slow down the aging process of the underlying roof materials, thus contributing to savings in roof replacements. Reflective roofs along with insulation can lower the energy consumption drastically. In addition, if it is a low-slope roof, it is more beneficial.
Owing to less heat being absorbed by the roof, energy consumption as well as thermal shock is minimized. Since less heat is absorbed and even the absorbed heat is emitted back, the energy or fuel necessary to air condition the building is reduced.
Another type of roof that helps in saving money and energy is a green roof, which comprises a vegetative layer grown on the rooftop. Such a roof is able to offer shade and avoid heat through evapotranspiration, leading to reduction of temperatures of roof surface as well as surrounding air. These roofs act as insulators, thus reducing the demand for energy necessary to cool and heat the building. Therefore, based on the nature of roof materials, money can be saved.