Installing foil insulation in an attic is a good way to reduce heat loss through the roof. The foil reflects radiant heat back into the attic, using plastic mesh coated with aluminium foil. It is important to use foil insulation with a government-approved Energy Star rating to show that the product is fit for purpose. Choosing a multilayered laminate foil insulation product is additionally important to negate the effect of attic dust and to prevent the need to install more than one layer of foil insulation.
Roll out a sheet of foil insulation between the undersides of two roof rafters with the foil facing down into the attic. Start 3 inches up from the base of the rafter to provide a gap to vent moisture.
Staple each edge of the foil insulation sheet to the rafters at 6-inch intervals, using a staple gun. Leave a 6-inch gap at the top of the rafters to allow moisture to vent from the roof at the ridge line.
Join end pieces of foil insulation together in between the rafters, using reflective metallised tape. Continue to staple foil insulation sheets to the rafters in the same way as before until the rafter installation is complete.
Roll out perforated foil insulation over fibreglass insulation in between the floor joists in the attic. Face the foil surface upward into the attic space.
Before starting, check that the roof has adequate ventilation to the outside to allow moisture to escape and prevent condensation inside the attic. Ensure no sunlight penetrates the attic where it could reflect off a foil insulation installation and cause a fire. Make the perforation holes larger on the foil insulation between the floor joists if you notice wetness in the underlying insulation over time.
Do not install foil insulation over attic lighting. This could create a fire hazard.