We are renovating/finishing the attic on a 1925 "craftsman" style bungalow house. The roof consists of true 2X6's. Because of ceiling height issues we are not able to make the roof rafter space deeper. Right now, we are planning to install "Dura-vent", then 4" of kraft paper backed fiberglass (R-13 or 15), then a 1/4" foil-foam-foil type insulation before sheetrock goes up. Do you all think this will work well? The foil stuff is a little expensive, will it be worth it? The foil company claims R-14.5 but I am skeptical because they only talk about "radiant heat". Any other suggestions?
I'm sure there will be other opinions, but putting foil in to work as a "radiant barrier"-which it does- it MUST be in a "free air" situation. It cannot be touching anything else- sheetrock, insulation, whatever. Anybody that tells you otherwise is lying or dumb. If it touches anthing it will go from radiant barrier to conduction freeway.
Also- putting foil directly above the ceiling is NOT a good idea. It needs to go up closer to the roof to reduce dust and dirt collection.
If you are replacing your ceiling- just concentrate on sealing ALL infiltration holes and put as much insulation as you can reasonably get up there.
Yes, what you are proposing will work well. Radiant barriers do not have to have an air space next to them as proven by several products with foil bonded to OSB that works well. The problem with putting a radiant barrier on top of attic floor insulation is that dust settles on the top surface and decreases the reflective qualities of the barrier. Your proposal should reduce the dust problem.