Radiant Barrier is material that is installed in attics to reduce summer heat gain and winter heat loss. This reduces building heating and cooling energy usage, saving money on monthly energy bills. The potential benefit of attic radiant barrier is primarily in reducing air-conditioning cooling loads in warm or hot climates.like we have here in San Antonio, Texas. I prefer the HeatBloc75 product. It is a spray on paint based spray that is retrofitted to the underside of the roof. We spray this product from inside the attic.
How is radiant barrier installed in an attic?
HeatBloc75 is applied to the underside of the roof decking from inside the attic. We use a Paint Sprayer to apply the product. Or, you could install it yourself with the foil product that blocks 97% of the sun’s radiant heat with: Foil Radiant Barrier. (this link is where we purchase our foil radiant barrier online – it is cheaper than buying from our local stores). It will take some time for you install the foil product, but you will save money not having to hire a professional. It is fairly simple to install can be done in one day (two at most), depending on the attic space you have to move around in.
How do radiant barriers work?
Radiant barriers work by reducing heat transfer by thermal radiation across the air space between the roof deck and the attic floor, where conventional insulation is usually placed. All materials give off, or emit, energy by thermal radiation as a result of their temperature. The amount of energy emitted depends on the surface temperature and a property called the “emissivity” (also called the “emittance”). The emissivity is a number between zero (0) and one (1). The higher the emissivity, the greater the emitted radiation.
On a sunny summer day, solar energy is absorbed by the roof, heating the roof sheathing and causing the underside of the sheathing and the roof framing to radiate heat downward toward the attic floor. When a radiant barrier is placed on the attic floor, much of the heat radiated from the hot roof is reflected back toward the roof. This makes the top surface of the insulation cooler than it would have been without a radiant barrier and thus reduces the amount of heat that moves through the insulation into the rooms below the ceiling.
Under the same conditions, a roof mounted radiant barrier works by reducing the amount of radiation incident on the insulation. Since the amount of radiation striking the top of the insulation is less than it would have been without a radiant barrier, the insulation surface temperature is lower and the heat flow through the insulation is reduced.
Radiant barrier can also reduce indoor heat losses through the ceiling in the winter. Radiant barrier reduces the amount of energy radiated from the top surface of the insulation, but can also reduce beneficial heat gains due to solar heating of the roof. The net benefits of radiant barriers for reducing winter heat losses are still being studied.
How does a radiant barrier differ from conventional attic insulation?
Radiant barriers perform a function that is similar to that of conventional insulation, in that they reduce the amount of heat that is transferred from the attic into the house. They differ in the way they reduce the heat flow. A radiant barrier reduces the amount of heat radiated across an air space that is adjacent to the radiant barrier. The primary function of conventional insulation is to trap still air within the insulation, and hence reduce heat transfer by air movement (convection). The insulation fibers or particles also partially block radiation heat transfer through the space occupied by the insulation. Purchasing some Solar Attic Fans will help get rid of the heat trapped in the attic. Well worth the investment!!!
Conventional insulation is usually rated by their R-value. Since the performance of radiant barriers depends on many variables, simple R-value ratings have not been developed for them.
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