Whole House Renovation – Insulation Question
We just purchased an early 90’s single story slab on grade home near the beach in northwest Florida. The house was originally built by a production builder, so the build quality is somewhat subpar. That being said, our plan is to gut it to the studs, remove all roofing and siding and essentially start with the frame, sheathing and decking. I havent confirmed the wall sheathing used, but I suspect its 7/16″ OSB because that is what is used on the roof. The house utilizes a standard combination of trusses for the various roof pitches and the attic isnt conditioned.
One of my main focuses initially with the home is what we are going to do to reinforce the structure in combination with modern insulation techniques and a fully conditioned building envelope. Being from central Texas and this being my first venture into building in Florida, I was shocked to see this home had standard OSB everywhere. It certainly wouldnt stand up to even a small category hurricane in my opinion. Its 600 ft. from the gulf, so I wanted to do something about that.
TLDR: My questions are as follows:
– If I repair the existing roof and wall sheathing (with like material), throw a few inches of polyiso on top, then layer it with 5/8 zip system (or just do Zip-R sheathing) and fasten it to the studs with screws, will I have enough sheer to handle what mother nature can dish out? It would be decking, rigid insulation, decking (with waterproof layer) in a sandwich fashion. I intend to insulate the cavity with mineral wool. Suggestions?
– Assuming my above sandwich config is suitable, can I attach my windows to the external sheathing or am I going to need to attach to the interior sheathing and build a buck? Again, open to suggestions.
Look forward to hearing from you fine homebuilders.
Spray closed-cell foam on the underside of the roof and into the stud bays and you get the great insulation plus a lot of structural support to boot. If you seal the entire attic you can turn it into conditioned space and use a smaller AC. Faster, easier cheaper and will save you money over the life of the house.
Understood, the problem is that my wife doesnt like the offgassing and environmental impact of closed cell, so its off the table for us.
Offgassing should be a temporary problem, and there are blowing agents available (if you can find a contractor who uses them) that have a GWP about the same as CO2.