Attic Insulation and/or Venting in the Southwest

[tom]

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

[Joe]

It's called Accuvent. We installed a bunch of it on a current project. Local Home Depot didn't stock it, so had to order from HD online and pay some shipping. Neither Lowes nor Menards has anything like it. Goes up fast and will work with R30 easily. Highly recommended.

Joe

[clare]

Inadequate attic insulation WILL be the largest heat gain that can be reduced economically. 15 inches of insulation and good ducted soffit vents with adequate roof ventilation (I'm partial to full length ridge vents for hot arid locations myself) is the best way to keep the heat out.. An insulated, reflective roof surface is a secondary method. Asbestos cement roof panels were very effective in Central Africa in the '70s - but are no longer an option here.

Large overhangs to shade windows, along with properly installed Low-E glass will also help. Large roof overhangs also shade the walls (which should also be well insulated).

Also a good idea to keep concrete driveways and patios well away from the house to avoid heat radiation and reflection into the house from them to a minimum. Grass isn't an ideal solution in Phoenix but is quite effective in reducing reflected/re-radiated heat.

[cm]

Andy,

More insulation, vent along the entire roof ridge, and vented bird blocks.

cm

[Woody]

reports:

>>> ~Mark.

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.

[Nova]

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.

[Doug Winterburn]

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...

[Bruce]

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

[RB]

Where do you get those flap vents, and how well do they seal ?

[Bruce]

On Fri, 19 Jun 2009 09:44:47 -0600, RB wrote (in article ):

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:

[Artemus]

I posted the product name on the 17th. Google lists the mfgr as the 2nd hit. Art

[tom]

Google "upducts". Tom