How does TechShield® compare to AtticFoil®? I get this question just about everyday. First, what is Techshield®? Techshield® is a roof decking material – usually OSB that has a sheet of aluminum foil laminated on one side. Techshield® is made by LP Building Products or Louisianna-Pacific Corporation and is probably the most popular brand of radiant barrier decking. Other brands are Solarboard by Norbord and Thermostat by Georgia-Pacific.
The main difference between Techshield® and AtticFoil® is that Techshield® is used almost exclusively for new construction or whenever a roof deck is being replaced. AtticFoil® is most commonly used inside the attic of existing homes.
For most new construction projects, I recommend using TechShield® (or another brand). The products work well, the cost of upgrading from regular OSB decking to radiant barrier decking is pretty minimal and there is NO additional labor cost since the Techshield® is installed just like a regular OSB roof deck. The foil side MUST face the attic air space (foil facing DOWN). If you install the foil facing up and then put roofing felt and shingles on top, you will get NO benefit.
Do they work the same? Yes and No. Techshield® works off a quality called EMISSIVITY. Basically, this is the ability to NOT convert energy to radiant heat. The roof deck will get hot and would normally want to emit radiant heat both upward and downward. By putting the foil on the bottom of the roof deck, it greatly reduces the ability of the deck to radiant heat downward. This is similar to taking two HOT baked potatoes and wrapping ONE with foil. The potato with foil will stay hot longer since the foil will reduce or slow down the amount of energy (heat) emitted.
If you were to wrap only half the hot potato with foil, then you have something similar to TechShield®. In this case, the potato would emit more heat upward through the area without foil compared to the side with foil. By reducing the heat emitted into the attic, this causes the attic contents (wood, insulation, framing) to be cooler. Combined with adequate attic ventilation the attic air temperature will also be significantly cooler.
AtticFoil® works off the quality of REFLECTIVITY since there is an airspace between the source of heat (the roof deck) and the foil. The radiant heat is STILL emitted by the roof deck, but hits the foil and is reflected back keeping everything below the foil cooler since the items never get a chance to absorb the radiant heat coming off the roof.
Don’t worry about overheating the roof deck – it will only increase between 2º-10º degrees.
By stapling to the bottom of the rafters, you will usually achieve a greater reduction in overall BTU’s coming into the attic compared to radaint barrier decking.
Can I make my own radiant barrier decking like TechShield using AtticFoil®? You can and it is VERY easy! Simply roll AtticFoil® Radiant Barrier foil out on standard 4’x8’ sheets of OSB or plywood. Then use a hammer staple and ¼” staples to tack it down. When installed over the rafters it will jut like a piece of radiant barrier decking. Or, if you want to install a radiant barrier for new construction, you can run the foil across the rafters and let it “droop” down about 4-5” between the rafters. By doing this method, the AtticFoil® will work off the reflectivity quality compared to the emissivity quality of foil. Be sure to leave a gap at the top and bottom of each rafter run for air to find its way up and out of the attic.