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  1. #40
    Join Date
    Apr 2002
    Posts
    11,808
    Quote Originally Posted by paul42 View Post
    That sounds good in theory, but is harder for some of us to do in practice.

    Any time an exhuast fan or the dryer runs (unless you have a condensing dryer), you are bringing in outside air to replace the exhaust. You may be able to confine most of that input to a fresh air intake provided for just that.

    But, that outside air comes in whether the AC is running or not, and if the AC is not running, it doesn't get conditioned. For my house, the AC is not running about 75% of the time on a hot day, and much less on cooler days.
    Intermittent exhausts are not a problem, constant exhausts can be disasterous. Look at my graph, some humidity spikes, they go right back down.

    The induced infiltration is coming in through path of least resistance not likely all 160 CFM for a clothes dryer comes in through your 6 inch intake even when the AHU is running, so you are sucking some through your walls as well as in from that vented attic of yours.

    In some cases it will sweat in your wall cavity. The wall should have a drying process like permeable inside finishes and also the positive pressure cycle will resume and dry it out.


    You guys are 30 years behind Canada on what it takes to build a tight house.
    Last edited by Carnak; 06-23-2008 at 12:43 PM.

  2. #41
    Join Date
    Apr 2002
    Posts
    11,808
    Quote Originally Posted by pstu View Post
    >>We saw dew points in the 80's here in WI a few weeks ago.

    Could it be possible this is in error? I poked around Weather Underground and for Madison WI saw max dewpoint reported at 75 for the past month. Average dewpoint was 56.
    http://www.wunderground.com/history/...lyHistory.html
    Then tried Dubuque IA and 76.5 was reported, with an average of 56. Although I took the 1st reporting station available, probably an airport would be more reliable than most amateur stations.

    By contrast, Ellington Field in Galveston TX reports over the past month max 77 dewpoint, and an *average* of 73. You can find similar conditions from almost any reporting station. When we say "high dewpoints" in hot-humid climates, it refers to chronic conditions not a rare occurrence for the record books. We cannot open the windows at night and expect to cool off and dry out.

    Regards -- Pstu
    Is it the heat or the humidity pstu?


  3. #42
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    Geez! And your UV seems up there too!

  4. #43
    Join Date
    Apr 2002
    Posts
    11,808
    lol the UV does look off the scale

    the worst days here for humidity control are when it is an 80 dewpoint and it is 80 dry bulb

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