Attic Insulation and/or Venting in the Southwest

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WhiteTea77581 wrote:

As hot air rises *and* the hottest air is in the attic, how do you propose it "migrate" to lower parts of the house?
My understanding (and what I did via an attic roof fan) is to cool the attic air so that living spaces adjacent to it are not next to as-hot attic air and thus reduce the AC demand in those living areas.
If there's one or more active fans on the attic vents (as I indicated and previous responder suggested) then the hot attic air would escape (i.e. be blown out) as cooler air, pulled into the attic via a fan entered. Thus lowering the attic air temperature. Thus lowering adjacent living space heat. Thus lowering AC demand. Thus lowering AC costs.
Typically, these are thermostatically controlled so that once they reach some "reasonable" temperature level, you don't continue to blow living space air into them.
~Mark.
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Woody wrote:

Attic/gable fans can make a big difference in the Arizona desert, lowering the attic temperature form 150+F to closer to the ambient 115F summer temp.
My unvented cardboard box solar cooker can reach close to 300F in the summer months. Was telling a former AZ resident about the solar cooker and he wondered why I bothered as I could probably accomplish the same thing by placing the cooking vessel in the trunk of the car...
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Andrew Barss wrote:

For energy efficiency I would recommend more insulation above the ceiling rafters.
Roof venting will lower the temperature in the attic crawl space but the main advantage of proper roof venting is that it extends the life of the roof. If you do vent the roof at the ridge you should also add soffit venting at least equal in area to that of the ridge vent for proper air flow. See:
http://www.roofhelp.com/ventilation_main.htm
http://www.cor-a-vent.com/pdf/balancedventilation.pdf
and
http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic 390
--
Jack Novak
Buffalo, NY - USA
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Nova wrote:

Almost totally non-applicable to the OP: * "Water vapor will condense..." Not in 0% relative humidity * "Frost will form....." In Tuscon? * "... problem of mildew..." Meh. * "Ice dams..." Again, in Tuscon?

Commercial brochure on ridge vents. Good explanation (except for the bit about exhausting hot, HUMID, air).

http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic 390
Typical government simplistic check-list. Superficial, but good, suggestions.
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Heh, heh. Absolutely right, HeyBub. Mr Barss, There are some folks here with excellent ideas. Namely: Make sure you've got soffit vents if you're installing ridge vent. Make sure your insulation doesn't cover the soffit vents. If it's worth doing, overdo it (insulation- wise). I'm not sure about those radiant barriers, as the underside of the decking _must_ breathe very well. I roofed for twenty-plus years in MI, and I'm looking at re-doing my roof here in Tucson pretty soon. I'm probably going with painted standing seam metal. I wish copper was more affordable, or I was richer... Tom
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HeyBub wrote:

I think people in Tucson still cook, take showers, etc. All produce moisture that will rise until stopped by a vapor barrier, often the roof. If there no venting...

Although I didn't write the article I'll give you this one.

See cooking, showering above.
<snip>
--
Jack Novak
Buffalo, NY - USA
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Andy,
More insulation, vent along the entire roof ridge, and vented bird blocks.
cm

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Soffit vents are 'required'. Use the rigid foam panels that keep a clear air path over the insulation where it meets your walls.
Also, if you use a swamp cooler, install a vented access door somewhere in your living space that vents into the attic. When the cooler is on, the air flows up into the attic (no need for an open window). With the cooler off, the vent flaps close and block attic air from returning into the house.
A 'whole house fan' installed in the same way can be used to flush cool air into the attic in the early morning and flush hot air out in the evening.
-Bruce

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Bruce wrote:

Where do you get those flap vents, and how well do they seal ?
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On Fri, 19 Jun 2009 09:44:47 -0600, RB wrote

I can't find a manufacturers name on mine, but its aluminum and has felt seals at the edges of the slats. Sealing has never been a problem (no bugs or other things get back through), but during the winter when I'm not running the cooler, I place a plastic cover over the vent to stop all air movement.
Here is a link to a similar vent:
http://houseneeds.com/shop/vent/qmark/qmarkatticshuttersbuy.asp
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I posted the product name on the 17th. Google lists the mfgr as the 2nd hit. Art

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Google "upducts". Tom
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