The federal stimulus plan's energy tax credits for insulation are based on the 2009 IECC, which raises the wall insulation requirement for climate zones 5 and 6 from R-19 to R-20. To meet this requirement, the R-value of the cavity insulation must be at least 3.63 per inch. Does this mean that standard R-19 fiberglass batts used to insulate 2x6 walls would not qualify for the tax credit? How about Icynene, an open-cell spray foam with an R-value of 3.6 per inch?
Q: I built a lot of homes in upstate New York in the 1980s using 2x6 studs, fiberglass batts, and a poly vapor retarder for the shell. Given the rising cost of heating and cooling, the owners are asking about energy upgrades to their walls. I'd like to suggest adding 1 or 2 inches of rigid foam on top of the existing OSB or plywood sheathing, followed by new siding. Would the presence of polyethylene vapor retarders make this a risky retrofit strategy?
Q: My painting subcontractor is recommending Thermo-Tek, a paint the manufacturer says is a radiant barrier. What can you tell me about products like this one or similar coatings made with something called ceramic microspheres that claim to have thermal characteristics and promise significant energy savings?
Understanding energy consumption and moisture movement in the homes we build is hard enough; rampant half-truths and misconceptions only make it harder.
Q: I'm building a house in North Carolina, which has a mixed-humid climate (climate zone 3). My local building inspector - backed up by his boss - requires a polyethylene vapor retarder on the interior side of cellulose-insulated walls. My insulation contractor says that interior polyethylene is not only unnecessary in this type of climate, but it may create condensation problems. What should I do?
