Attic Insulation and/or Venting in the Southwest

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

Reply to
Andrew 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.

Reply to
Master Tang

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.

Reply to
ransley

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 .

Reply to
ilbebauck

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

Reply to
WhiteTea77581

"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.

Reply to
Swingman

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).

Reply to
HeyBub

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.

Reply to
J. Clarke

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

Reply to
Lew Hodgett

I'd assume (?) the installer of the ridge vent would know that. The one that installed mine did.

Reply to
Master Tang

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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.

Reply to
sligoNoSPAMjoe

I'd go one better than just adding active fans at either end of the 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:

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~Mark.

Reply to
Woody

So he should suck in the 113 degree heat and pump it into his house?

Reply to
Master Tang

A couple years ago, it was summer time. The company I was working for, we had been installing an air handler and AC in the attic of a house. We had a roof company install a power vent. After they installed, I temporary wired it in, and turned it on. You could feel the difference almost immediately, with the fan dumping the hot, humid attic air out. I'm a believer in roof power vents based on that.

Reply to
Stormin Mormon

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:

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Reply to
Nova

Absolutely. Nothing else will help as much as a Powered Roof Mounted Attic Fan with adequate makeup air via perforated soffits / gable vents.

Reply to
ilbebauck

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

Reply to
WhiteTea77581

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...

Reply to
aemeijers

How thick is the insulation now? Blown insulation will settle over time and perhaps not have the same R value.

In a pinch, staple cardboard from the vent and above the blown in material,

Spend a little time and find out why your doors and windows, leak most energy. Smoke pencil, exotic incense helps show a draft.

DIY home audit

Reply to
Oren

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).

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Typical government simplistic check-list. Superficial, but good, suggestions.

Reply to
HeyBub

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