Radiant Barrier can be attached to the attic (exterior) side of a knee wall to cut down on radiant heat gain or heat loss in the winter. It is recommended that insulation be encapsulated on all six sides with a rigid air barrier like sheathing or foam board. If possible install sheathing on the attic side first and then cover with radiant barrier.
1. You should use a perforated material (ARMA FOIL™) for this application.
2. If there is no air barrier installed on the attic side, consider adding sheathing or foam board to encapsulate the insulation on all six sides.
3. Unroll the Radiant Barrier and staple to the exterior side of the wall facing the attic, overlapping each run by about 2 inches.
4. You should tape the seams to help reduce air infiltration.
Vapor Barrier:
If your local climate or building code calls for an interior vapor barrier, Non Perforated Radiant Barrier can be used as a vapor / radon barrier. It will reduce moisture inside the house from passing through into mass insulation.
1. You must use non-perforated (ARMA FOIL-VB™) material for this job.
2. Unroll the Radiant Barrier and staple to the interior side of the wall studs and insulation.
3. Overlap each run by about 2 inches.
4. To create a true vapor barrier, you must tape all seams and penetrations.