I have a modular home with a 3-1/2 -12 roof pitch in northern Indiana. Straight 28X44 gabled roof with 18 year old original asphalt shingles. When I need to reroof I would like to add insulation over the existing roof. I have cathedral ceilings and scissor truss construction, so this is my only option to add insulation. Can anyone reccomend the best way to do this? I already have R-20 , but want more
Should I use Rigid foam? With furring strips or just long screws all the way through to the old roof?
Or the foil and bubble wrap type insulation?
Would I be better off to go over the insulation with plywood and shingles or metal roofing? What about venting? is it necessary if I go over existing roofing?
I don't have a preference except I want to do it myself and get the best bang for my buck$$$ ANY IDEAS ARE WELCOME
you should vent the upper roof system,the original roof work work as a separator ,if you like,I feel you would be fine with insulating over the top with R-38 or better(or if you can afford it seal with closed cell insulation/super R-values),just be sure to leave room for proper venting channels,as well as venting,bathroom +dryer vents up to vent thru the upper roof so as not to create condensation problems----(ed call me)