As we become more energy efficient and environmentally conscious, our awareness of products like radiant barrier systems become greater. You may have previously heard of the technique, but you may not have fully understood how the process works, and how it can help you in the long run. Generally, radiant barriers are installed in the home to deflect heat, thus lowering the costs to keep your home cool in the summer. It is most commonly installed in the attic, but can also be installed within the roof. These barriers will actually deflect (actually re-emit) radiant heat, as opposed to absorbing it.
Radiant heat travels in a straight line and becomes absorbed by any solid material. What does this mean to you? Typically, without radiant barriers, when the sun is heating up your roof, it’s the sun’s radiant energy that is causing this. Then, via conduction, that heat travels through the roof materials and into your attic. Conduction occurs when heat travels from hotter areas to cooler areas. Additional heat travels into your house through the roof’s radiant heat at this point, and travels to your attic’s interior and floor. Point being, your house is being penetrated by large amounts of heat in two different ways, from the roof alone! Radiant barriers reduces the radiant heat transfer from the roof to the interior of your attic.
Radiant barriers are graded on three levels:
- Emmisivity – This is expresses as a number between 0 and 1, and it is the amount of radiant energy that is emitted back onto a black surface of equal area and temperature. The higher the number, the greater the amount of radiant energy being emitted.
- Reflectivity – This is either expressed by a number between 0 and 1 or as a percentage between 0% and 100%. It is a measurement of how much radiant energy is reflected by the barrier. A higher number or percentage means that more radiant heat is being reflected back.
- Angle – The angle at which the radiant heat strikes the surface. Perpendicular (aka a right angle) is the best.
Obviously, these types of barriers are more effective in warmer climates, and can lower your cooling costs by 5-10%.
Radiant barriers come in a variety of forms. The reflective material, which is usually aluminum, is applied to either one or both sides of the material that is being used as a barrier. This can be roof shingles, reflective chips, roof sheathing, etc. Since these barriers don’t provide additional thermal insulation, they can be combined with insulation to achieve the desired result. Installation of the barriers, particularly in roofs, is best done during new home construction, but houses can be retrofitted to have this capability. While you are certainly able to install a radiant barrier yourself, it does require special skills and tools, which is why a professional is recommended.