What is the best option for my ceiling project?
Luke writes from Portland, Oregon: “I have 2×8 rafters in my ceiling (16″ centers) and I’m wondering what the best insulation would be. I’m considering 2 layers of r-15 fiberglass insulation. Would that give me r-30? Would a layer of 2×6 insulation and a layer of 2×4 insulation give me more r value? I know that I could attach a 2×4 furring strip and put the R-30 2×10 insulation in, but I don’t want to do that if possible.” Answer: Yes. Two layers of R-15 uncompressed will give you R-30. Adding R-19 and R-13 insulation without furring out the rafters would compress to approximately R-25. Furring out with 2×4’s would be the proper way to do this. This would allow the proper space for sufficient R-Value.
