The How, What, and Why about Radiant Barrier insulation
How Radiant Barriers Work: Reflective Paint vs. Foil
Those of us with dark-colored roofs know how hot it gets up there during the summer. Intense solar heat radiates indoors through the rooftop, baking the attic like an oven. The hot attic, in turn, conducts unwanted heat to the rest of the house, pressuring cooling systems to work harder and driving up utility costs.
It’s one reason your bills are so high during the dog days of summer. How do you prevent this scenario? How do you ensure your insulation is performing with maximum efficiency? The trick is to ease the load on your A/C system by reducing heat gain. That’s what radiant barriers are for.
Radiant barrier foil vs. paint
Radiant barriers use aluminum to minimize solar gains by reflecting the sun’s rays back, away from the air-conditioned building. This action increases energy efficiency and lowers the associated cooling energy costs. Radiant barrier insulation makes good sense in hot and sunny climates where it supplements conventional insulation.
There are two main types of radiant barriers: paint and sheets of foil. Radiant barrier paint is simply ordinary water-based paint intermixed with pure, powdered aluminum. Radiant barrier foil isn’t quite like what you find in your kitchen, although it is made of sheeted aluminum.
Commercial-grade aluminum foil acts as a near-perfect thermal mirror, reflecting around 95 percent of radiant heat. In contrast, paint reflects 75 percent, under ideal conditions. Unfortunately, the ideal conditions under which radiant barrier paint is effective aren’t usually found in the real world.
As a result, barrier paint products are not technically considered effective enough to be called radiant barriers, according to research published by the Reflective Insulation Manufacturers Association (RIMA).
Where does radiant foil help the most?
Radiant foil barriers only work where there is sufficient airspace between the foil and the surface to which it is attached. This airspace is a key performance factor. For this reason, the ideal foil barrier installation tends to be in the attic. Happily, the attic also happens to be where the most unwanted thermal gains occur in the average home.