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in reality it's hard (and probably expensive) to proactively cool house with AC during summer at hot/sunny regions. I live in a house with rather good insulatio
by tguvot 4y ago
in reality it's hard (and probably expensive) to proactively cool house with AC during summer at hot/sunny regions. I live in a house with rather good insulation (the one mandated by code) in south bay, yet all the walls getting rather warm and even if you try to precool air with AC walls with bring temperature back quickly
My solution was to install whole house fan which runs through the night when temperature drops to 16C-14C. It allows to both replace air with colder one multiple times and due to improved air-flow to cool off the walls.
After I shut windows close at morning most of the houses stays within comfort zone ( < 22C) till 6-7pm even on 40C days
- mrguyorama 4y agoIf you can feel that your walls are warm I don't think that's good enough insulation. The whole house fan solution is great though.
- tguvot 4y agoi have walls insulated according to california build code. it's not really possible to add more insulation to them, unless you rip them off and do spray in insulation. insulated attic with radiant barrier and insulated floors. i just checked with IR camera, most of surfaces in the house are now 22C-24C. After a few days of 40+C walls ill go to 25-26. some walls (south side of house) even higher. There are few little spots where insulation doesn't sit properly - it will be around 28C. The biggest offender is skylight. Temperature near top of it can get to 60C. Edit. I think most people simply do not realize what temperature have internal and external walls in houses and how it interacts (or counteracts) AC. If you will go to read greenbuildings/passive houses forums, there are a bunch of discussions about thermal mass of the walls
- reaperducer 4y agoit's not really possible to add more insulation to them, unless you rip them off and do spray in insulation. Actually, it's possible to inject foam insulation into walls without ripping them off. It goes in through small holes, or through utility boxes. Plenty of companies do that. I've even seen it advertised on TV in California.
- tguvot 4y agoI know. But injectable foam insulation usually going into empty walls. I already have butted fiberglass in there. I don't think it's viable to make laparoscopic wall surgery to remove fiberglass . I did a quick google, and looks like you can do injectable foam over fiberglass. But I am not sure how much R it will add, but I am sure that for cost of of injectable foam + wall repair, I can get another hvac and run it for next 10 years... I did consider recently to double walls on sunny side of the house with few layers of foil backed foam boards.
- mrguyorama 4y agoDo you have any actual numbers for what is up to code insulation in California? California is a very temperate climate. I wouldn't exactly expect their code to have the highest insulation requirements. Also, building codes should be considered the minimum. I am keenly aware of how much thermal mass walls hold. My apartment is 3 external walls that are constructed pretty much only of a few inches of concrete, bare. The result is that after a full day of summer sun, even though it drops to 64 degrees outside at night, my air conditioner cannot keep it 76 degrees or lower inside. It's crazy. It's worse in the winter when I can feel the walls sucking heat out of my apartment.
- tguvot 4y ago>Do you have any actual numbers for what is up to code insulation in California? California is a very temperate climate. I wouldn't exactly expect their code to have the highest insulation requirements. R-15 for 2x4 or R-21 for 2x6. Not highest numbers in USA I guess and after you buy house that already "exists", it's expensive to change it. >I am keenly aware of how much thermal mass walls hold. My apartment is 3 external walls that are constructed pretty much only of a few inches of concrete, bare. The result is that after a full day of summer sun, even though it drops to 64 degrees outside at night, my air conditioner cannot keep it 76 degrees or lower inside. It's crazy. It's worse in the winter when I can feel the walls sucking heat out of my apartment. Whole house fan is the way to go. If you can't install one, I think a couple of strategically placed window fans over night to create some air flow through the house might work better than AC I did some research on preventing walls from getting too hot (my room wall on the outside hits 170F i think). Narrowed it to - Transparent paint with some particles that reflect sun/reduce heat gain - Awning - Shade sail - Trellis and grow some vine to cover the wall.
- rsync 4y agoWhole house fans are really great. It’s cheating, a bit, to live in a place that drops 20-40 F at night … but even if we didn’t, the ability to turn every open window into an air conditioner is a great trick.
- tguvot 4y agoYes. It's really amazing. First thing that I did after bought house last summer was to install whole house fan. Due to it we used hvac to cool house for less than 36 hours in July-October timeframe (only at days when temperatures were above 40 for few days in a row or when night temperatures didn't went down below 20)
- bluGill 4y agoI'm going to tear mine out. It helps a little, but it leaks so much conditioned air when not in use i'm convinced it is a negative overall.