Foil Insulation Installation Tips, Tricks & Techniques
Radiant Barrier Foil Installation Info
Generally there are two methods of installation for radiant barrier insulation.
Warm Climates like Houston and Dallas.
the rafters (bottom of the roof) inside attic or laid out over the top of the insulation.
Cold Climates
laid out over the top of the insulation.
There is also a "HYBRID" method for very steep or tall attics and very low hard-to-reach attics.
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Which installation Method is Best?
Warm Climates - In places like Dallas and Houston, we are generally more concerned with KEEPING THE HEAT OUT. Therefore, it makes sense to put it as close to the heat source as possible. When applied to the bottom of the rafters on the roof deck the foil will make the attic significantly cooler. This is ideal since your ducts are probably in the hot attic. When you drop the temperature in the attic the A/C system will work less because of reduced heat gain into the ducts. Also, since most duct systems have some leakage, your system will be pulling in cooler attic air into the mix.
The other method is to lay the foil across the insulation in warm/hot climates. This method works very well and is often the only only option in attics that have a very high or low pitch roof. In fact, I was in an attic yesterday (7/07/07) and the temperature on top of the insulation was about 122º F. But, on the section that had the radiant barrier laying accross the insulation the temperature (when you lift up the foil) was about 108º F. This method of installation is usually pretty quick and easy compared to stapling to the rafters. As with any efficiency upgrade be sure to have proper attic ventilation and to check for leaky air ducts in your HVAC system.
Cold Climates - We are more concerned with KEEPING THE HEAT IN. Therefore, putting the Radiant Barrier Foil on top of the insulation works fine. Foil insulation helps in two ways. First, it will reflect the radiant heat loss BACK into the living space. Second, it will reduce the internal convection within the existing insulation. Warm air rises inside the insulation, and cold air rushes in to replace it. The foil (IT MUST BE PERFORATED) will reduce this transfer of air by "sealing" the insulation. And, allow for moisture to pass through the perforated material. CRITICAL NOTE: You must be careful NOT to cover any source of moisture from inside your home such as a bathroom exhaust fan. It is very important that bathroom and kitchen fans are vented to the outside of the attic or at least past the foil insulation.
Rafter Application
- Run foil ACROSS the rafters. Measure out long pieces. A helper works best.
- Start at the bottom near the eve and work your way up. Use 1/4" or 5/16" staples.
- Staple BOTH ENDS first, the foil will stay up, it is very strong. Then staple the rafters in between the ends.
- Use 3 - 5 staples for each 48" section of rafter
- You MUST leave a gap/opening at the top of EACH rafter run (see pictures) for the heated air to escape out of the attic
- Don't worry if your actual attic vents are BELOW the top edge of the foil. Hot air will all end up in the top of the attic and find it's way out EVEN if it goes down a foot or two to get to the wind turbines or roof vents.
- Cut holes in foil below wind turbines, attic vents or other "holes" for air to exit the attic.
Attic Floor Method for WARM climates.
- Existing Insulation should be level and have no bald spots.
- Start in the corners of the attic and work towards the exits.
- Roll out sections and cut around supports, ducts, and other penetrations. If ducts are on the attic floor, cover them too.
- Use a pole with nail (see install pics) to push into far corners, low spaces, vaulted ceilings or difficult to reach areas.
- Overlap the foil at least 2-3 inches. You can secure the pieces together with foil tape.
- Mark decking, or walk paths with colored tape or spray paint.
Attic Floor Method over insulation: For COOL climates
- Existing Insulation should be level and have no bald spots.
- Start in the corners of the attic and work towards the exits.
- Roll out sections and cut around supports, ducts, and other penetrations. If ducts are on the attic floor, cover them too.
- Use a pole with nail (see install pics) to push into far corners, low spaces, vaulted ceilings or difficult to reach areas.
- Overlap the foil at least 2-3 inches. You can secure the pieces together with foil tape.
- Mark decking, or walk paths with colored tape or spray paint.
- Be sure NOT to cover any exhaust fans from bathrooms or kitchens.
