What to do with a thermal disaster?
I am trying to determine a cost-effective strategy for improving the efficiency of my home, specifically the roof.
It is a 1969 ranch in Tucson, Arizona. The house is a thermal disaster if there ever was one.
Here is how the roof is constructed: Low-slope (half inch per foot), 2X10 rafters (built-up membrane roof above, drywall ceiling below), insulated with foil-faced batts of a whopping R-9.6. There are eave vents but no ridge vent. Ceilings are code-minimum low at the eaves, 8′ at the ridge, with ductwork in a dropped soffit under the ridge. I guess you’d call it a vented cathedral attic but with ceilings this low, “cathedral” is not exactly a word I would choose. The closest thing the house has to an “air barrier” would be the drywall, which of course is poked with a million holes and leaks air like a sieve.
I’ve thought of three options. Option 1 is to attempt to pull as much of the foil-faced batts out as possible, dense-pack the rafter bays with cellulose, close the vents, move the air barrier to the exterior, and pray. Tucson is in climate zone 2B so an unvented attic like this can work pretty well. It’s simple and the work is easy-peasey lemon squeezy. Unfortunately I won’t be able to remove all the foil; some of the rafter bays are 20 feet long. I should be able to get maybe half of it out without removing drywall. Just how concerned should I be about the foil facing that gets left?
Option 2 is to leave the assembly more or less alone, and use my insulation/air sealing budget to install extra solar panels to cover the ridiculous heating/cooling load.
Option 3 is to remove all the drywall ceilings and replace all the insulation. I don’t think this option has a payback period, ever. It’s also not nice to the landfill.
I’m leaning strongly toward Option 1 but I have this nagging fear that it could be a Really Dumb Thing, which is why I am posting this here.
Thank you for any ideas or thoughts you might have!
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