Useful products to reduce summer indoor heat without air conditioning?
I live in northern part of Los Angeles County where summer highs are typically in the 90’s and can get over 100 degrees. Our home is a single story home with a north/south facing gables without an air conditioner yet with energy efficient windows & shades plus R-30 attic insulation laying on the attic floor.
During the summer I manually open the windows and shades in the evening and close them in the morning. The roof is supported with 2×4 rafters running in east & west and the attic is 6 feet tall. I wonder if there is more I can to reduce indoor summer temperatures?
I read the bad news about radiant barriers and the like such as reflective insulation . Yet can this or another system be effective and cost efficient for me if certain guidelines are followed?
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Replies
Ken,
Your house might be a good candidate for a whole-house fan.
For more information, see Fans in the Attic: Do They Help or Do They Hurt?
I can think of four general kinds of things you can consider:
1. Improve the speed and effectiveness of getting the house down to the outdoor temperature in the evening--the whole house fan Martin suggests.
2. Decrease the rate at which the outside heat gets inside during the day. Lighter colored roofing material, sealing air leaks in the envelope, and more attic insulation even though you already have a pretty good amount would be examples of things in this category. It's hard to tell without visiting whether there are good opportunities in this category.
3. Reduce the amount of heat generated inside during the day. For example, if you have electronic equipment turned on that doesn't need to be on during the day, turning it off could help a little.
4. Increase the thermal mass inside the house. For example, if you like the look of a giant slab of granite for a coffee table, it would get cooled off at high when you have the whole-house fan running, and then would stay cool during the day helping keep the house cool.
Of those four, it sounds to me like the first is the most likely to be practical and significantly effective.
You'd have to beef up the rafters to something better than 2x4s to support it but shading the west facing pitch of the roof with a solar array would both bring down the peak cooling load, and offset the evening CAISO grid peak load. The west side gets the highest gain during the afternoon when air temps are already peaking and the house has been soaking up heat all day. Shading the roof lowers that PM gain.
The peak output of the array also occurs during the PM grid load ramp, and is still delivering power near the evening peak, which is all good for power grid stability & longevity, far more useful than mid-day gain of south facing panels in an already well developed solar market like L.A.. The net total kwh produced by the array is lower than south facing panels, but the value of that power is higher. (Not that they would pay you more for it under current net metering rules.)
http://dqbasmyouzti2.cloudfront.net/content/images/articles/4CAISO03-16-2014.jpg
If you wanted do use some of that power to run a mini-split air conditioner during the array's peak output times it would reduce the export to the grid during the evening ramp but you'd still be reducing the grid peak rather than adding to it.
If you don't want to spend the money on the solar there are many third party solar companies competing for roof space at no cost to the homeowner. A third party ownership power purchase contract at a modestly reduced price and no annual increase usually works favorably in the long term- don't get sucked into big discounts now, with 3% annual rate hikes or you'll be paying more than retail within 10 years.