|Installing a radiant barrier in the walls is done just like the cathedral ceiling method. When you are trying to keep heat from escaping, it is best to have the foil closest to the inside of the room as possible, while still maintaining an air space on one side of the foil. You will add the foil over the insulation in the walls, then create an air gap and finish with the Sheetrock.|
Primary Goal: Keep Heat INSIDE
This method is used primarily in colder areas that are concerned about keeping heat inside the room/home.
Just like the other wall method for keeping heat out, think in terms of layers and how the heat is flowing from the INSIDE of the home through the wall to the OUTSIDE of the home. The purpose of adding radiant barrier to the wall is that the radiant barrier will act as the first line of defense against radiant heat loss, and then the regular insulation will be the second line of defense against conductive heat loss.
Here are the layers as they should be installed:
For similar installation instructions, read Installing Radiant Barrier in a Cathedral Ceiling to Keep the Heat In.