I almost hate to ask this question after reading the 65+ answers on Insulated Windows, but I'm a little bewildered on this one. I'm preparing to install the roof on our house that we are building and have been proposed "double bubble" aluminum foil as the best solution. But it is only 1/4 inch thick!! And the "R" value is only 1.5. This is insane. I get that the foil will reflect back the conductive heat generated by the metal roof, but geez, the R value is miniscule. Does anyone know of the best way to insulate the underroof and the area above the ceilings? I've looked into the blown in cellulose insulation, fiberglass insulation batts like what is used in the USA, and that could be a viable solution as long as I can make sure the underroof area is water tight sealed. I will make sure that there is sufficient are flow from the under soffit vents and am thinking of a small wind turbine on the roof to aid the air flow as long as I'm confident that it can be installed without leakage of water. Any experts out there that can provide suggestions? Thanks.
