I’m going to explain how an installed radiant barrier works?
All of the heat from the sun is transferred to Earth in the form of radiant heat. This is heat transfer without actual contact with the heat source. When your roof absorbs radiant heat from the sun, it heats up. About half of the heat, or energy, will transfer into the attic. Radiant heat is the invisible part of the light spectrum; it’s the part you feel, not the part you see.
For example, if you stand near a fire on a cold night, you feel the radiant heat on your front side, but your backside may still be cold since it’s not receiving any radiant heat. Radiant heat travels at the speed of light until it’s either absorbed or reflected.
Normally your attic insulation will absorb all of this energy and it too will start to heat up. Eventually, this heat will make its way through the attic insulation and into the home. Traditional attic insulation will only slow down the heat transfer process. When you install a radiant barrier between the roof and the attic insulation, by either stapling it to the bottom of the roof rafters or laying it out over the attic insulation, it breaks this path by reflecting the radiant heat back towards the roof and helps keep the attic insulation from getting as hot.
By keeping the attic insulation cooler, we can significantly reduce the amount of heat transfer entering the home by making the regular attic insulation more effective. So think of it this way: the radiant barrier is your FIRST line of defense against radiant heat, and traditional attic insulation is your second line of defense against conductive heat flow.
Since your home is exposed to both types of heat, you need a different product for each one. A lot of people talk about a COOLER ATTIC, which is nice but really what we want is cooler attic insulation.
This means less heat will enter the home. If less heat enters the home, then you spend less money to get the heat out and your home will be more comfortable. It’s really that simple.