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Old 03-26-14, 07:28 PM   #1
leaning
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Question Using attic heat and crawlspace cool.

Hello!

I having been lurking for awhile, but I figure I'm going to stick my neck out there and see what happens:

Stats:
House in NW GA. 1 story, brick exterior, crawlspace, and attic that is 1/2 finished and 1/2 not. We like to keep 1st story at 69F year round. Attic gets up to 120F in summer. Crawlspace stays at 60F with high humidity and some mold (!)

Projects:
1) We have a company coming that is going to do the attic and crawlspace:

  • a) Attic : General air sealing (reduce air leakage from living space by seal/insulate recessed lights, seal/insulate attic access door, seal major attic bypasses. Seal chaises, top plates as needed, sealing around light fixtures, electrical penetrations, caulking door frames or window frames that may leak, etc.).
  • b) Attic: Fiberglass insulation 10" (open blow): place tape measures thru out attic that will remain in attic. L77 encapsulated pro pink fiberglass, Certainteed
  • c) Attic knee walls: Add Foam (high density) & 1'' Polyiso - Rigid Board
  • d) Attic: Vent & Insulate existing two bathroom exhaust fans through roof (vice to attic space)
  • e) Crawlspace: 1.5" Closed cell foam on Crawlspace walls
  • f) Crawlspace: Encapsulate rim joists with 2 Foam (high density)
  • g) Crawlspace: 12 mil Duraskrim liner Waterproof/Vapor Barrier
2) Door blower test showed our house is "too tight", so I installed a passive air intake (backflow flap, filter, damper pipe) going to HVAC intake. http://contractingbusiness.com/site-...0000053450.gif

3) Attic has exhaust fan that turns on at approx 100F and runs all the time in summer.

4) Crawlspace vents are shut and sealed.

Thoughts I would appreciate feedback on:

1) Attic gets way too hot and crawlspace is way too cold and moldy. Maybe I can run a pipe with fan to suck air from attic and send it to crawlspace. Makeup air to attic from soffit vents and gable vent. Excess air in crawlspace out CS vent hole in other side of house farthest from fan.

2) Use radiant barrier in attic attached to roof joists. This would reduce temp in attic, so making insulating attic floor not so necessary. Company doing attic work doesn't like whole radiant barrier thing. Says that with reflectics there is little reduction in temperature, and they have gone back and replaced/removed several of these systems from houses over the years, and not to waste money on those.

3) We seriously would like to take advantage of the hot attic (in the wintertime) and the cold crawlspace (in the summertime). That's some good temperature air that it we could be filtering and using in the living space and turn off the air conditioner and heater to save money.

Interested in everyone's thoughts and ideas.

Regards,

Leaning

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Old 03-27-14, 07:49 AM   #2
gasstingy
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Talking

Good morning Leaning, and welcome aboard. Lot's of fine people here, plenty more knowledgeable than I, but here goes anyway. We do have a little in common, the climate and damp crawl space being most obvious. I live in North Alabama in a single story brick home and suffered with a damp crawl space and mold issues.

I have automatic damper foundation vents and they are nearly worthless in my opinion for moisture control. I installed the heavy vapor barrier material including running it up the foundation walls about 12", taped the seams and noticed no significant improvement. Since I was mostly tired of the mildew on the floor joists in the crawl space, I pulled out all the fiberglass insulation and threw it away. Then I wiped down all of the exposed lumber with a mixture of ~ 90% hydrogen peroxide and ~ 10% distilled vinegar. The lumber all looked brand new when it was done. The very next day, I had all the wood under the house sprayed with 2" of closed cell foam. Don't try this with open cell foam as moisture can pass through open cell, not closed cell. Now, I don't worry about mold anymore. {In many cases, professionals recommend sealing up the crawl space and insulating the floor and around the perimeter and then including this in the conditioned space.}

I'm not a huge fan of fiberglass insulation. Personally, I'd use cellulose. The energy audit guy recommended I used suggested we install 5" additional insulation in my attic when we were talking about down-sizing our central unit, so we added 10". All blown insulation settles, after all.

As all things mechanical break down eventually, have you considered installing a continuous ridge vent? I don't know if you can do this yourself or have to hire it out, but it's an option. Our last house was an inferno in the attic and the attic fans ran from daylight to hours past dark before they'd shut off. Our present house has a continuous ridge vent and continuous soffit vents all the way around the house. This attic is cooler, but to be fair, the roof is more steeply pitched and is galvalume versus black asphalt shigles. Still, there is nothing to break down, and no rumbling in the attic from the fans.

More will surely welcome you soon and we all wish you well. When you make changes, please document the changes so you can share your experiences, and take pictures. We all like pictures!
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Old 03-27-14, 10:01 AM   #3
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Quote:
Originally Posted by leaning View Post
...Use radiant barrier in attic attached to roof joists. This would reduce temp in attic, so making insulating attic floor not so necessary. Company doing attic work doesn't like whole radiant barrier thing. Says that with reflectics there is little reduction in temperature, and they have gone back and replaced/removed several of these systems from houses over the years, and not to waste money on those...
Here is a success story regarding the use of a radiant barrier in the attic.

Another possibility is a white roof. Some people are prevented from doing this by their home owners association, for you it might be possible.


Best,

-AC
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Old 03-29-14, 07:40 AM   #4
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Why would a home owners assoc. not want white roofs?
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Old 03-31-14, 08:56 AM   #5
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Home owners associations set rules on a bunch of stuff, and typically don't allow anything that differs from said rules.
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Old 03-31-14, 02:04 PM   #6
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I'm with you on using attic heat for winter. You might get some good ideas from what I've been doing, described here:

http://ecorenovator.org/forum/solar-...bottom-up.html

It has the advantage of using a radiant barrier which keeps the attic (and house) cooler in summer. It also uses that same radiant barrier to collect and concentrate any hot air collected up there and brings it down to the house via a fan in winter. The control and construction regime for using a system like this has to be well thought out ahead of time. It's not something you do over a weekend or two.

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