Radiant barrier foil is a newer product that is growing in popularity when it comes to increasing your home's energy efficiency. The three main types include two-sided with micro perforations, two-sided without micro perforations, and two-sided with bubble wrap in the center. In this article, we will look at applying two-sided, micro perforated radiant barrier foil to an attic floor.
The first thing to consider in all home improvement projects is safety. Potential hazards in this project include low clearance areas where you can hit your head on a rafter or nail, areas that lack flooring where you might accidentally put a foot through the underlying ceiling material, extreme heat that could induce heat exhaustion or heat stroke, and loose wiring that could deliver a nasty shock when contacting the foil product.
You may want to wear a hard hat for protection, and you will need to take note or mark where the attic flooring is and is not. Use four-foot lengths of board to safely walk on joists that lack floor material. If you must work in heat, realize that extended time in higher temperatures can make you very ill, and take preventive measures. Put a yard sprinkler on the roof to run water and cool the attic temperature. Run fans in the attic to move the air, or remove an air conditioning duct to make it blow cool air in the workspace. Inspect all wiring, cables, and junction boxes for loose wire or loose connections, and repair or have an electrician repair the faults. Also take note of any exhaust fans and canister lights or any other heat source. These areas must have a clearance of four to six inches on all sides for proper venting. If you have any waste vent that vents to the attic space, temporarily plug these vents with rags. The methane and other exiting gases should not be breathed.
You will need a space to mark out and cut lengths of foil. If you have adequate vertical clearance, you can suspend the foil roll from a rafter with a jig and note how high above the floor the roll is. That will be your standard length in feet that you can work with. Alternately, have a large space downstairs or in a garage to lay out, measure, and cut the foil. The cut foil lengths can then be rolled like carpet or folded accordion-style to make it easier to take to the attic space. Try to work from the points farthest from your attic entrance, to help avoid tearing or moving your previously laid pieces.
Some attics will allow the installation of the foil to run perpendicular to the joists, and this is the best direction. If your roof pitch is too shallow to allow running the foil perpendicular to the joists, it will need to be cut to run parallel to them. Most radiant barrier foil rolls are four feet wide. If your joists are 24 inches on center, simply cut the foil lengthwise to allow it to be placed on the insulation easily. While a four foot wide roll cut in half will not lie flat in the 46.5 inches of space between three joists or trusses, this is acceptable. Joists which are 16 inches on center will simply need to be cut in thirds width wise. In all other areas, allow for two inches of overlap on all sides. Also keep the foil 12 inches away from end walls and soviets or rafter vents to allow for proper ventilation.
The foil does not need to lie flat against the insulation. It works best with an airspace, so the natural peaks and valleys in the insulation are helpful. It also does not necessarily need to be taped or stapled on the seams. If it will be later walked on over a flooring surface, staple or tape it in enough places to prevent displacing the foil. For long runs and tight spaces, the challenge is how to put the foil where it belongs. Place a nail at the end of a length of thin wood trim or plastic pipe. Use the nail to move the foil into place. If you are running the foil from the center of an attic area in both directions, put a nail in each end of the wood or plastic pipe to prevent having to turn the tool around for the opposite side.