While results will vary from climate to climate, attic installed radiant barrier will reduce heat gain through the ceiling by roughly 40%, which translates into a 17% average reduction in heating & cooling costs. The local climate and the installation technique chosen, will affect the performance of the radiant barrier, so be sure to choose the right installation for your local climate.
While this 17% figure holds true for many climates using a typical installation, it will vary from place to place. Many independent studies and radiant barrier users have tested their results and reported energy savings varying from as low as 12% up to as high as 39%.
Below is one such independent study in which the attic temperature of two similar neighboring houses where tracked over the course of one day. As you can see from the image below, the attic with radiant barrier(blue) performed quite nicely and stayed very close to the ambient temperatures outside(green) when compared to the house with no radiant barrier(red).
Factors Determining Radiant Barrier Effectiveness:
- Attic Ductwork – If ductwork or air handlers are located in the attic, the temperature of the attic area will affect the efficiency of the HVAC system. Using a radiant barrier to control attic temperatures will increase the HVAC system’s efficiency, thus reducing energy costs.
- Existing Insulation – If existing attic insulation is less than a R39, a radiant barrier installation will help to stop excess radiant heat. Homes with a R39 or higher ceiling-insulation, and have no ductwork in the attic will not achieve much energy savings from a radiant barrier installation.
- Cold Climates – In climates where the majority of annual energy usage goes towards heating the structure, a radiant barrier on the floor of the attic, above the insulation and ductwork will provide substantial energy savings.
- Hot Climates – In climates where the majority of annual energy usage goes towards cooling the structure, a radiant barrier stapled to the bottom of the roof rafters will provide maximum energy savings.
- Mild Climates – In more mild climates where neither heating nor cooling is used much, a radiant barrier installation will not create massive energy savings. However, the radiant barrier will increase the overall comfort of the structure while providing small to moderate energy savings.