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Home Air Direct 03-14-2009 09:35 AM

AH In Extreme Cold Attic Question
Beenthere, hvaclover, yuri and others,

A question was asked on one of my blogs that I would like some thought on. Below is the question and my response. Am I thinking about this correctly? What have I missed? My knowledge base comes in part with experience in my geographic region (Midwest). Do any of you Nanooks of the North have any experience here that would help?

Thanks Guys (and gals if appropriate).


  1. David on March 14th, 2009 1:17 pm Can you install an air handler up in a non-insulated attic here in Quebec where night temp often goes down to minus 30? This also would include about 160 feet of flexible ductwork insulated with 2-inch fibreglass leading to 7 ceiling vents into the rooms.
    The manual says “for indoor installation only” and I don’t trust the sales rep who says there’s no problem putting the thing “up there”.
    Thanks for the info
    a worried David
  2. Home Air Direct on March 14th, 2009 1:48 pm David,
    The answer is Yes and No. An electric furnace (air handler) with strip heat will work fine in an attic. Usually the biggest concern is evaporator coil condensate freezing, but I assume AC is not your concern at -30. So, considering the heat, your thermostat will only know that the inside of your home needs to meet your specified temperature. Therefore it will run the unit in your attic until it satisfies that requirement. The problem will come from the invasion of extreme cold at the air handler. At -30, this will be an extreme loss of efficiency due to your run times being longer to finally satisfy the indoor temps that will ultimately result in higher utility bills. Insulating the air handler will help this greatly.
    So, your salesman is right. It will work. It just will not be as efficient as it should be.
    Good Luck
    Home Air Direct

yuri 03-14-2009 10:29 AM

It can work but I would not recommend it. The cabinet on an electric furnace has minimal insulation, probably R2 so it would lose heat like crazy. It is also hard on the motor to start when it is -30 and the unit may rust internally in the off season if it is humid up there. I would probably refuse to go up there for any amount of time if it was that cold and it would be hard to get some techs to service it.

Home Air Direct 03-14-2009 05:24 PM

Yuri, thanks for the response.

After considering it some more, I responded back to the OP and said that under his circumstances, I would not recommend the attic installation:no:.

Another more serious thought comes to mind, and that is since the attic is not insulated, the heat loss from the air handler and the ducts themselves could cause snow to melt, run and refreeze, causing ice dams. He indicated that in his area this can be a serious problem.

I also can only imagine how much humidity would form if heat is escaping into -30 temps. I can see it snowing inside of his attic:santa:

-30 and "Feet" of snow. I am so spoiled living in the lower Midwest, unless you factor in the every-other-day tornado warnings for the next 3 months.


yuri 03-14-2009 05:34 PM

Tornadoes, snakes and all kinds of problems we don't have up here, HaHa. Gotta watch out for roaming polar bears for a couple more weeks. Then the mozquitoes take over.:)

beenthere 03-14-2009 06:24 PM

Actually, heat escaping into the attic through the duct insulation. Would lower the humidity in the attic.

It would only be heat, not moisture that was escaping.

Insulation, looses a great deal of its R value at -30.

So better to have the furnace and duct work in a conditioned space in those temps.

Home Air Direct 03-14-2009 06:40 PM


Originally Posted by beenthere (Post 244625)
Actually, heat escaping into the attic through the duct insulation. Would lower the humidity in the attic.

It would only be heat, not moisture that was escaping.

Thanks.....I stand corrected on the humidity. Sometimes the mouth just goes off without thinking:oops:
The final advice I gave this guy was to give up some conditioned space for this installation. He apparently has a contractor that is about to create a problem for him, telling him it will be fine:no:

biggles 03-14-2009 09:02 PM

attic installations are considered an indoor installation, they mean actual outdoor in the weather might be worth it to keep the air handler in a closet with a vertical installation.the resistance heating is only rated for a certain temp rise when it runs the truer the return from the space is the more efficent is will run.

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