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  1. #1
    Join Date
    Jan 2006
    Posts
    25
    I am about to request the trane XL16i for my
    home, and a variable speed air handler? Is this
    o.k. for a foam insulated conditioned attic? Or
    are these units normally placed in other areas
    like garage, inside the house, etc.?

    My builder has reservations about the attic
    not being vented in Oklahoma City. Is there
    a way to make sure that moisture does not
    become a problem there?

    My guess is leaks from ducting would be the most
    probable source of humidity or moisture, and then
    maybe condensation?
    I will have 5-6 inches of foam on attic roof
    underside, with the walls also foamed. Next problem is choosingopen vs closed cell foam. Open is more able
    to transfer vapor, and closed cell is not.
    What do you "the experts" recommend? thanks

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,318
    Friend of mine is a foamer, I can refer you to him with foam questions. As long as you have good access to the attic, planking down, lights, the attic would be fine for the air handler. It will be very comfy up there. You won't have the usual duct loss/gain of a traditonal attic.

  3. #3
    trane 19xli does not cost that much more and the benefits would greatly be worth it. install some soffitt vents.
    most furnaces are installed in attics. whoever invented them
    never worked on one an texas. oklahoma is really just far north texas. wouldnt have a football team with us.

  4. #4
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    Originally posted by airworx
    install some soffitt vents.
    The type of construction he is talking about makes the attic part of the conditioned space. Ventalating it would defeat the purpose.
    If more government is the answer, then it's a really stupid question.

  5. #5
    Join Date
    Mar 2004
    Posts
    1,042
    Ask your builder if he has ever built a walk-in closet without putting supply and return vents in there.

    You can do that and get away with it just fine because there's no humidity source, and you don't really try to keep that space at exactly the same temperature as the rest of the house. If you want to do even better, you put a supply or return vent in there.

    This is not a traditional attic; those are basically outdoor spaces except that they have a roof on top to keep the rain out. The ventilation in a standard attic is meant to let the heat out of the attic- the heat that radiates in from the hot roof- and in the process they bring in humid air. What you are asking your builder for is only loosely an attic, then. The way it's being insulated, you should call it a height-restricted mechanical room, or a utility space. The only thing that will make it different from any interior room in the house is that you probably won't put up drywall, and it won't be quite as roomy.

    There will be no moisture source at all in the attic. The ducts won't sweat because 1) they're still going to be insulated and 2) it's going to be about the same RH in the attic as it is in the house. Just to be safe, set it up with a little supply and return venting (maybe 50-100 cfm) from the ventilation system that will be in that space. That will keep the "mechanical room" almost as well conditioned as the rest of the house, and that should be plenty.

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