I’m considering buying and building a kit house. The only problem I have with it: The largest roof rafter they’ll put in is a 2x10, which only allows for R-30 fiberglass batts in a cathedral ceiling. I would like to fur out the underside of the rafters with 2x2s or 2x3s to allow for R-38 batts (which need a 2x12). [I’ve already considered and rejected rigid foam insulation on the ceiling, for reasons of cost and final ceiling finish.]
Is the added weight of the furring strips (well … furring boards) going to be too much of a strain on the roof structure?