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  1. #1

    Hmm

    When I do furnace tune ups, I sometimes run into people who have gotten a new mid or high effic furnace and they say that they now have big humidity probs where there was none before the install of the new furnace.

    Can anyone give me some reasons for this other than changing the structure or integrity of the home? When customers ask I would like to give them some answers for this or possibly solve the prob if it is a simple solution

    Thanks in advance

    don

  2. #2
    Join Date
    Apr 2002
    Posts
    11,808
    I grew up about 7 hours east of you and I always found that when you upgraded an old standing pilot/drafthood furnace with a mid or high effificent gas furnace there was always a humidity problem.

    Air would go up the chimney 24/7 with the old furnace and this would cause dry air to infiltrate in all the time in the winter.

    When they upgraded the furnace to a mid or high efficiency, they now have induced draft, air only goes up the chimney or out a sidewall vent when the furnace is firing.

    They lost the 24/7 ventialtion when you changed the furnace. They need dry fresh air in the winter to control humidity.

    Can try a humidex, a fresh air intake, an HRV.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  3. #3
    Join Date
    Nov 2001
    Posts
    1,874
    I have had a guy tell me that know that he has a new 90% unit his house has a bad humidity problem.
    He did have an 80%.
    He has even had his resest lighting fictures sweat and drip . I went up in the attic, moved all the insulation away from his can lighting. The insulation was holding moisture and the lights would be warm and make the condensation drip from them.

    Still don't know how to fix the problem, his style of lights can't be covered. so he was told.
    My house shows a constant 32% humidity level. And when it gets in the teens outside my windows sweat even at 32%.
    seems worse this year.

    [Edited by Toolpusher on 02-05-2005 at 07:44 PM]
    If you try to fail, and succeed.
    Which have you done ?



  4. #4
    Join Date
    May 2001
    Location
    Kansas City
    Posts
    2,729
    Must be a Canadian thing, we use humidifer's here. Even new tight house's get to dry, I've seen the grain crack open on new cabinets. Older house's should have a lot of infiltration of cold dry air that gets even dryer when heated.

  5. #5
    Join Date
    Apr 2002
    Posts
    11,808
    A lot of the older homes get retrofitted with new windows, weather stripping, caulking. Probably downdrafts waiting to happen.'

    They upgrade furnace and all of a sudden humidity problem.

    A house running a humidifier is a drafty house. Maybe the tight house smith is talking about has a fresh air intake.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  6. #6
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    you all should be careful about making blanket statements as if they apply everywhere in the world!!

    if you bring in outside air here in Huntsville AL, you would bring in lots of humidity!! I have to fight to keep %RH below 70 -- right now! Most of the time the RH out doors is over 85!

    one needs to reexamine the needs of the house BEFORE just replacing an existing unit = do a load calc!! then examine the ductwork and determine if it is suitable for the load and compatable with the new equipment.

    else = ass/ u/ me

  7. #7
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,596
    Originally posted by cem-bsee
    you all should be careful about making blanket statements as if they apply everywhere in the world!!

    if you bring in outside air here in Huntsville AL, you would bring in lots of humidity!! I have to fight to keep %RH below 70 -- right now! Most of the time the RH out doors is over 85!

    one needs to reexamine the needs of the house BEFORE just replacing an existing unit = do a load calc!! then examine the ductwork and determine if it is suitable for the load and compatable with the new equipment.

    else = ass/ u/ me
    As many post have implied, high winter humidity indicates a leaking pipe, water intrusion, or a lack of ventilation. High outdoor relative humidity when the outdoor temperature is below 50^F is meaningless. Outdoor air even if 40^F 100%RH dries the home out, provided the home is heated to +68^F. When outdoor temperature is +60^F, com-bsee concerns apply.
    The humidex unit promotes year around humidity conrol as a benefit. Caution, fresh air ventilation during high outdoor moisture (+60^F) adds moisture to the space and promotes mold/dustmite growth.
    50-75 cfm of fresh air ventilation provides oxygen, purges polutants, controls winter moitsture, and makes a home wet when the grass grows(+60^F dewpoints). Fresh air is a "must have" item for health. Avoiding high humidity indoors is also a "must have" item.

  8. #8
    Join Date
    Apr 2002
    Posts
    11,808
    Originally posted by cem-bsee
    you all should be careful about making blanket statements as if they apply everywhere in the world!!

    if you bring in outside air here in Huntsville AL, you would bring in lots of humidity!! I have to fight to keep %RH below 70 -- right now! Most of the time the RH out doors is over 85!

    one needs to reexamine the needs of the house BEFORE just replacing an existing unit = do a load calc!! then examine the ductwork and determine if it is suitable for the load and compatable with the new equipment.

    else = ass/ u/ me
    It was a blanket statement concerning homes in northern Canada as the OP was in Winnipeg and I was about 400 miles east of there.

    People upgrade furnaces and get a humidity problem.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

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