Radiant Barrier Foil DIY

Place a sturdy ladder under your attic access hatch and remove or slide the access door ajar, to provide entry. Put on respirators (for yourself and an assistant). Armed with a bright flashlight and a tape measure, climb into the attic space, making sure you keep your footing on the floor joist beams. Have the assistant pass up small sheets of 3/8-inch plywood that will fit through the access opening. The sheets can be 3 feet to 5 feet long, and they will serve as platforms to lay or stand on over the support beams.

Measure the length and width of the attic space by stretching your tape along the side and vertical expanses. This includes the sloping slides of the roof area, or just the vertical sides and top roof section of a square attic. Include the triangular sections at each end of the structure, if it has a V or gabled roof.

Use pen and paper to tabulate how much barrier foil you will need by multiplying the length times the width for both angled sides or the vertical areas, for the rectangular design. If you wish to place barrier tape between the joist beams, and not over the rafters, you will need 24-inch-wide barrier tape instead of the 48-inch width. Stapling over the rafters with the larger role is recommended, rather than cutting individual 24-inch strips. Use the plywood sheets to lay or stand on as you move along.

Cut your strips of barrier foil to the length of your attic space. You can trim the excess length (or height) after you have worked from the bottom up. For over-the-rafter installation, stretch the 48-inch strip between yourself and your assistant from end to end, starting at the bottom and about 2 inches above the floor. Use a staple gun to staple the foil to the end rafter, using about four or five staples (evenly spaced) in the support beam. Staple the foil strip to the end.

Instruct your assistant to stretch another 48-inch strip of foil from the opposite end, and repeat the process for the next level up. Use a 1-inch to 2-inch overlap over the previous strip. If you come to a support beam, use a utility knife to cut a slit in the middle of the beam, so the foil wraps around the support beam and continues on the other side. Make the same type of slit for a vent pipe and a larger cutout for any type of chimney flu or wind turbine ventilator. Cut out any vent profiles on the walls of the attic, once you have the strip stapled in place.

Cover the side, or angle roof section, with successive strips until you reach the top roof support beam. If you have excess foil when you reach the top, let the excess hang. Then use a utility knife to trim the excess off, but leave a 1-inch to 2-inch gap from the edge of the foil to the roof support beam, which will serve as ventilation.

Cover all sides of the attic with foil, meaning the end walls, sloping walls or vertical square walls. You will not need to install the barrier foil over the floor space, only the surface that is subjected to overhead or horizontal, direct sunlight on the roof panels.