Attic Insulation and/or Venting in the Southwest

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I'm looking for advice and ideas for improving energy efficiency in my house, especially heat from the roof and attic.
I own an older house in Tucson, and we are trying to do what we can to decrease our electricity (mostly air conditioning) bills. The house has a peaked roof, with a low attic that has minimal access. The attic has some blown-in loose insulation between the ceiling joists, and nothing on the underside of the roof itself (and putting anything there is essentially impossible). We have some degree of venting -- there are small vents on the two end walls near the peak, and two passive vents (rotary type) on the roof, about four feet down from the peak.
I've heard various things, some conflicting, about how to better the situation:
a) blow in a lot more insulation. b) increase airflow using soffet vents (aka birdboard). c) do both d) do both, but with some sort of a channel up from the soffet vents to above the insulation.
e) tear the roof off, put a lot of money into a high-tech roof treatment. The curent roof is light-colored shingles, and in quite good condition.
    Anyone living in the Southwest have advice on what the best move is?
Thanks,
Andy Barss
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I'd put more insulation in then the vents. I wouldn't mess with the roof. Too expensive for your return.
Consider a ridge vent. They are not that expensive and supposed to be the most effective.
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Master Tang wrote:

If you don't have the soffit vent the ridge vent doesn't help all that much--air has to come in before it can go out.
The channel from the soffit to above the insulation is easy--you get it in premolded plastic from Home Depot for not much money.
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I'd assume (?) the installer of the ridge vent would know that. The one that installed mine did.
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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
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Pay for an energy audit and get a blower door test done. There are many ways to increase efficency that will be outlined by an audit, you may find windows or another issue more important.
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ransley wrote:

Maybe Tucson is big enough so he can find somebody who will do that. I tried around here- none of the Utility, Insulation, or HVAC companies offer the service. I'd have to pay hundreds of dollars to have somebody come over from the Big City to do it.
-- aem sends...
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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.
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You definetly need a powered roof mounted Attic Fan which comes with its own thermostat that you typically set at 95 f. (on) . I wouldnt be without one in the South. Ive had them on ALL of my houses with tremendous improvement..plus it makes your roof deck last longer. The Attic Fan would pull in cooler outside air thru your two end grilles and exhaust the superheated attic air very very well. You can get them at any Lowes, Home DePot, or Menards store. About $80 . Forget about static Ridge Vents...they are virtually useless -- you need to FORCE the air out of the attic . Further, I would lay batt insulation in your attic on top of the blown in insulation after you smooth it out so its level. Use R30 batt insulation which will come 24' long and 15" wide (also available 24" wide) and is 9.5" thick. I just did mine and immediately noticed the difference. These two improvement done together will make your inside much more comfortable as well as reduce the runtime of your cooling system (as much as 30%) thereby saving you money . Ive vacationed in Tucson 7 times over the years and almost moved there in 1980 . I spent my honeymoon on Mt. Lemmon at SummerHaven .
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On Jun 17, 4:16pm, "Stormin Mormon"

Absolutely. Nothing else will help as much as a Powered Roof Mounted Attic Fan with adequate makeup air via perforated soffits / gable vents.
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I have seen about a one-third reduction in electricity bills by blowing in insulation in the attic. Make sure you cover electrical fixtures before blowing in the insulation.
If you don't have thermostatically controlled blowers in the attic, get some.
Solar screens also help a lot.
Andy
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Andrew Barss wrote:

"d", although not the whole story, is probably the closest for old construction.
Some other things to take into consideration for hot climates:
Vented roofs reduce the total solar heat gain by roughly 3 to 5%. Consider installing ridge vents instead of the passive rotary vents along with your vented soffits. Clay or concrete tile shingles can reduce the solar heat gain by 10 to 15% in a vented roof. Color is not a big an overall factor as you might think; material is, however. Dark colored clay or concrete tile shingles outperform light colored asphalt shingles, but in general light colored roofs do perform better than dark, although it may not be significant taking material into account.
Radiant barriers can have a significant effect on reducing solar heat gain on asphalt shingled roofs, not so much on clay or concrete shingles. Best is a product like "tech-shield" used as decking, better than none at all is the spray on radiant barrier paint. Keep in mind that you need at least 1" of void space below the radiant barrier for maximum effect. Radiant barriers do perform significantly better on vented roof systems.
Basically, unvented roofs with clay or concrete tile shingles and R-19 insulation or greater; and vented roof systems, with mechanical equipment and ductwork within the conditioned space, and R-19 or greater ceiling insulation, perform the best in the Southwest.
If you do decide on "e", your best bet for hot climates is a design that incorporates AC ductwork and air handlers within the building thermal barrier, and a vented roof with clay tile or concrete tile shingles and an R-30 or greater ceiling insulation.
If the AC ductwork and air handlers must be located in the attic spaces, then go with a design that incorporates an unvented roof, creating a conditioned attic space for the mechanical equipment.
Do your homework and find some "green" building seminars in your area ... the woods are full of them.
--
www.e-woodshop.net
Last update: 10/22/08
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Snip .

To add to what Swingman has mentioned here, my parents had the rediant barrier sprayed into their attic and had 8 more inches of insulation blown in. This was done last year in July. So far this year they have averaged a 20% savings in hours used on the months that they have been using the air conditioning.
I can tell you right now that pay back will be a long process if you only consider your electricity savings to the cost of the improvement. I can tell you that you will probably save money on equipment repairs and or equipment replacement. The AC simply does not have to work as hard. My parents keep the thermostat at 76-77 degrees all summer long and the temperature stays there. Last year before the improvements the inside temp stayed at 79-81 degrees. Additionally there are no longer any "Hot Spots" in the house. Regardless of which room you are in the temp seems to be the same.
Last, I built a wood and Hardiplank store room about 5 years ago. I chose to use Radiant Barrier Decking over standard Decking. The cost was about $4 per sheet more. The store room has one door that stays shut and no windows. It has sofit vents only. The store room does not feel any hotter in side than the out side temperature. IMHO well worth the small additional expense as Christmas candles do not melt nor do I when I am inside the store room.

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I used to live in Tucson for 25 years and have seen many ways to cool the attic. The rotary vents can only exhaust air if there is a wind and by having them mounted lower than the intake vents convection is against you. You'll need to force vent the attic. A powered vent, either AC or solar powered, is the best solution if you have only air-conditioning. If you also have a swamp box there is a product called "Up-Dux" made in Phx that installs in your ceilings and lets cool air inside the house exit up into the attic. This helps immensely and costs nothing to run. Another less effective option is to paint the roof white, which usually is the only option for flat roofed houses. Art

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Andrew Barss wrote:

In addition to the other wonderful suggestions, I'd offer the following:
1. Light-colored roof. A good idea, BUT... drive around your city. Do you see any? No? Why not? The reason is that they discolor in a ghastly fashion from the junk in the air. In places like Rome, they have permanent pressure-washer crews prowling the city cleaning off the marble statues. IF you're lucky, one side of the roof may be completely unseen by the picky-public and you could get away with a white roof there.
2. You can't have too many soffit vents. If your ENTIRE soffit is a vent, that's good. I'm not sure what birdboard might be, but if it's anything like the perforated Hardiplank, it's probably insufficient. While the holy plank stuff has a lot of holes, their total combined area is miniscule.
Experts agree that the unobstructed soffit vent area should be 1 sq in for each 1 sq ft of attic space (again, more is better).
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"Andrew Barss" wrote:

As the old saying goes, "Advice is usually worth what you pay for it."
As someone else suggested, contract with a reputable firm and have a total energy audit performed.
It will cost a few $, but it will save many times that cost.
Otherwise you are flying blind.
Lew
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On Wed, 17 Jun 2009 18:06:57 +0000 (UTC), Andrew Barss

    I would suggest blowing in more insulation for now. In the future your shingles will fail and then you can remove them, add a ridge vent and open up the soffits as much as possible. At that time I would consider adding a layer of insulation (high efficiency foam) on the current roof, after removing the shingles, and then the new roof over that.
    The cost of energy is just going to continue to climb.
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Andrew Barss wrote:

attic. I'd also add a whole house fan, mounted in the floor of the attic (ceiling of the living area) to pull cooler air up from the house into the attic. This air will be cooler than the outside air and will create a cool airflow throughout the house.
Here's a fact sheet from consumer reports: http://blogs.consumerreports.org/files/whole-house-fans-1.pdf
~Mark.
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So he should suck in the 113 degree heat and pump it into his house?
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My parents had one of those in the 1950's before they had AC.
In hot, humid weather the who house fan basically blows the hot air around.
I think the goal is to blow the hot air out of the attic so it doesn't migrate into the house.
Andy
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