I'm looking for help in insulating my 1950s San Diego house. A second story was added in the 70s and a gas furnace + A/C was added about 10 years ago in the unconditioned space above the downstairs bedrooms. This space is also right next to my master bedroom.
I'm in IECC Zone 3B/C. Highs here are between 60-85F year round and it never gets below 50F at night (rough I know). The problem is that when it does get to 85F, the vented attic can get to 120-130F since the roof gets a lot of sun. That means at midnight, the outside air temp is 70F and my master bedroom is 90F+. The air conditioning can run all night and not get it below 80F. Then again the next day, the master bedroom is a comfy 75 all day until around 4:00PM.
The wall between my bedroom and the unconditioned attic space is R13 fiberglass (crappy piecemeal) with the insulation faces pointing both directions. The other side is exposed to the attic. I have air sealed all electrical boxes with spray foam. The attic only has pull-down stairs to get in, so a full 4'x8' board will not get in without major destruction. The attic has multiple soffit and gable vents and no fan besides a plug-in stand fan I've been using.
I've done my research and asked around and come up with these options:
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Put up a perforated radiant barrier on the attic rafters and gable walls.
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Fix the insulation so all faced batts point towards the living space and put up additional, rolled fiberglass insulation. I was thinking unfaced R30 horizontally across the studs.
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Put up an air barrier (Tyvek / house wrap) behind the fiberglass insulation on the attic side of the wall.
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Spreading loose cellulose around the attic to bury the ducts, while staying away from the furnace.
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Install a temperature-controlled attic fan.
My gut usually tells me to overdo things and to do #s 1-5 on this list, but what would you do here?
Best Answer
I am not clear at all from your description how your rooms are laid out. One thing I'd try is not on your list I'd install an attic fan on one of the gable vents with a thermostatic control. This will keep the attic from getting much over the outside ambient temperature. This will probably be money well spent even if you have to add insulation etc. as well.
Outside the box - solar on the roof might give actually take that radiant energy and turn it into electricity and money, rather than nuisance heat in your attic. I don't know what the current situation is in California but I think at one point the subsidies / incentives made solar a good buy for the homeowner.