How to Install Rigid Insulation in a Reflective Wall

Install reflective insulation first in new construction, before any rigid foam or other sheathing is applied. Tape it to roof decking inside roof rafters or truss chords, and install rigid foam board on the outside of the decking; foam board typically is nailed to decking with broad-headed nails. Place it inside wall studs and add rigid foam exterior sheathing. Use a tape supplied by the reflective insulation manufacturer.

Put reflective insulation over foam board if the rigid insulation has already been installed. Tape it to the foam board or put it on the other side of the roof or wall; if rigid foam has been nailed to roof decking, put reflective insulation underneath the roof in an attic or between joists in a ceiling. Avoid using foam board with a foil or barrier face in combination with reflective insulation; two barriers create a trap for moisture, which can create condensation problems.

Use rigid foam insulation as an electrical barrier around reflective insulation. Avoid direct contact of reflective insulation with electrical boxes or wiring; its aluminum is highly conductive of electricity, and can lead to shocks or fires. Putting rigid foam between the reflective insulation and wiring will block conductivity of current.