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  1. #66
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,327
    Chad,
    before you write us all off...
    try what teddy bear suggests:
    Operate you fan "on" mode for a couple days to test "the condensation in the ducts" theroy.

    personally...I'm not sure about that, but would be interested in what you find out. as teddy bear
    says..its a learning experience.
    better to resolve what is happening than to live with it...right?
    investing a week of your time may provide a solution to your RH issues.

    living in the south...I've seen the issues caused by the whole chinese drywall fiasco.
    corrosion of copper in electrical, hvac causing homes to be re-wired, hvac system completly
    changed out...breathing issues. its nothing to make light of.


    keeping the thread on track is always difficult. so just ignore what doesn't apply & use
    could help you. insulting homeowners is not the intent of this forum.


    best of luck
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  2. #67
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,645
    Quote Originally Posted by clllclal View Post
    Thanks for the input. I will try that. So I set the heat to setpoint and when the temp. is satisfied, the heat will cut off but the fan will continuously blow? Take for instance at this point in time. The temp. outside is going to get around 72 degrees today. It will not be hot enough for the A/C to run or cold enough for the heat. Should I still let the fan run?

    Thanks again everyone

    Chad
    This condensation will only occur when the attic temp is below the dew point of the air in the home. Sun on the attic roof or warm outside temps mean a warm attic and no condesation potiential in the ducts. No need to run the blower when the attic is +65^F.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  3. #68
    Join Date
    Mar 2012
    Posts
    51
    Quote Originally Posted by teddy bear View Post
    This condensation will only occur when the attic temp is below the dew point of the air in the home. Sun on the attic roof or warm outside temps mean a warm attic and no condesation potiential in the ducts. No need to run the blower when the attic is +65^F.
    Regards TB
    One more quick question. My tstat gives the option for "on" or "circulate." Which one would you recommend I use?

    Thanks

    Chad

  4. #69
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    Circulate. You may want to keep the dehumidifier running until that ductboard dries out.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  5. #70
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,327
    a building science article that in part addresses what is going on is Chad's house.
    only part of the article...see picture #4

    http://www.buildingscience.com/docum...rces/retrofits


    Photograph 4: Window Condensation - Interior moisture levels go up due to reduced air change and relative humidity adjacent cold window surfaces rises sufficiently to condense water. How to fix this problem? Lower the moisture content of the interior air with dilution ventilation or warm up the surface of the windows by replacing the windows with better windows or do both.

    So Far:
    1-reduced Rh by adding dehumidifier
    2-are the kitchen vent fan & bath fans vented out of the attic?
    3-leaving fan set in on position..in case there is condensation in the duct work. as per Teddy Bear's postings.
    4-windows...see my first post about metal frames of windows & condensation.

    also...while letting the blower run in winter to resolve the issue of moisture in ductwork that is potentially ongoing,
    the side note to that is fan setting in the summer.
    for cooling season when a/c use is constant, you set the fan to auto.
    reason for that is...RH removed by a/c will collect on coil, when fan is set
    to on position...it releases this moisture back into the house when compressor cycle ends.
    when fan shuts down as unit shuts down, the moisture then is released to the pan
    and drains away.

    so...are your kitchen & bath fans vented out of the attic??

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  6. #71
    Join Date
    Mar 2012
    Posts
    51
    Quote Originally Posted by energy_rater_La View Post
    a building science article that in part addresses what is going on is Chad's house.
    only part of the article...see picture #4

    http://www.buildingscience.com/docum...rces/retrofits




    Photograph 4: Window Condensation - Interior moisture levels go up due to reduced air change and relative humidity adjacent cold window surfaces rises sufficiently to condense water. How to fix this problem? Lower the moisture content of the interior air with dilution ventilation or warm up the surface of the windows by replacing the windows with better windows or do both.

    So Far:
    1-reduced Rh by adding dehumidifier
    2-are the kitchen vent fan & bath fans vented out of the attic?
    3-leaving fan set in on position..in case there is condensation in the duct work. as per Teddy Bear's postings.
    4-windows...see my first post about metal frames of windows & condensation.

    also...while letting the blower run in winter to resolve the issue of moisture in ductwork that is potentially ongoing,
    the side note to that is fan setting in the summer.
    for cooling season when a/c use is constant, you set the fan to auto.
    reason for that is...RH removed by a/c will collect on coil, when fan is set
    to on position...it releases this moisture back into the house when compressor cycle ends.
    when fan shuts down as unit shuts down, the moisture then is released to the pan
    and drains away.

    so...are your kitchen & bath fans vented out of the attic??

    best of luck.
    The kitchen is not. I'm not sure about the three bathroom exhaust fans. Looking in the attic above where one of the fans are located, there is a vent pipe that exits the roof, but this might just be for plumbing. Could the exhaust fans be tied to that. I know I'm not very much help on this. Shame on me for not knowing more about my own home. At the very moment, I am running the fan in the "on" position with my stand alone dehumidifier running full blast.

  7. #72
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,327
    I never vent bath fans thru the roof. they just don't have enough 'push' to go up and out.
    instead I vent into soffits. you can tell which joist bay has venting because you'll see light from
    outside.
    you'd have to first...find the bath vent fan, if its covered with cellulose, turning it
    on will help you to locate it. if it has a backdraft damper..or not...it will blow the cellulose
    around..helping you to find it.
    backdraft damper needs to be installed so that when fan is off, the damper closes.
    suprising the number of bath fans that the bd damper is installed incorrectly.

    usually bd dampers are the same size as dryer vents. I use a foil flex dryer vent
    attached to bd damper. lenght of venting will easily reach into soffit, cutting off
    excess vent. you want to keep the vent run as straight as possible.
    I use mastic tape to attach venting to damper, then damper to bath vent fan.

    code also says that bath fans are to be vented out of soffits. but to go
    from venting into attic to venting into soffit suffices for existing homes.

    bath fans & stove fans that vent into the attic introduce a lot of humidity into attic.
    when bath fans vent directly into insulation they can over time cause mold growth.
    stove vents vented into the attic put grease particles in the attic.

    a fireman once told me that the cause of a lot of attic fires was from
    stove vents terminating in the attic and not being vented outside of attic.
    codes dictate this, but in existing homes...we get away with a lot more than new construction.


    at this very moment...I'm consitering turning the a/c on. 75 degrees with 70% RH outside today!
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  8. #73
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    One may get away with "cutting corners" by trying to vent bathroom exhaust out of the attic soffits in hot climates, but it should NEVER be done in the colder climates. This is especially true if you have your attic air sealed and improve the insulation levels. What happens is that the air sealing & improved insulation makes your attic colder - because it is no longer being warmed by your homes conditioned air leaking into the attic- and all of that warm moist air that you think you are "venting" through the soffit is simply being drawn back into the attic, where is condenses on the cold roof. As seen in this video, it can lead to some serious problems.
    http://www.youtube.com/watch?v=pne-iMqVfOY
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

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