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:
Put up a perforated radiant barrier on the attic rafters and gable walls.
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.
Put up an air barrier (Tyvek / house wrap) behind the fiberglass insulation on the attic side of the wall.
Spreading loose cellulose around the attic to bury the ducts, while staying away from the furnace.
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?