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  1. #1

    Humidity and Condensation Issues During the Winter

    Hi All,

    I have an 2 year old log home located in western Pennsylvania. The house is very air tight, having a paneled roof system and log walls. During the winter months (temps below 40 degrees F) condensation starts to form on the bottom of the windows throughout the home. This has been an issue since we've moved into the home and we are concerned not only for the mold forming on the windows because of the moisture but also if there is moisture throughout the home that we aren't noticing that could cause future mold issues and unhealthy air quality. I have researched several options including Whole House Air Exchangers (w/ ERV's) and Whole House Dehumidifiers. I am looking for advice from anyone who has experiences like this, what they did, how it helped, and also advice from other HVAC professions who have experiences with these problems and fixes for it.

    Here is some other useful information about the house:
    -We utilize radiant heat during the winter months underneath the flooring in the basement and main floor (no heat pump or other heaters)
    -We have an A/C unit that we use during the summer months (May-September) with duct-work through out the house
    -Ceiling fans in most rooms running at all times
    -Little to no fresh air entering the house during the winter except when we open doors to enter/exit the hous
    -The only time the house gets a lot of fresh air is during the spring when windows are open and cool summer days/nights

    Thank you for all your help and advice!

  2. #2
    Join Date
    Aug 2004
    North Richland Hills, Texas
    You need air exchanges.

    In your area, I think the the pros and cons between either an ERV or HRV would be a wash.

    If the higher up front and operating costs are not a big issue, a whole house dehumidifier, with fresh air ventilation, would great for year round ventilation and humidity control.
    If more government is the answer, then it's a really stupid question.

  3. #3
    Thanks Mark,

    I've asked several HVAC guys in my area and none of them seem to be familiar with air exchangers. The guy that did all of the air conditioning and duct work in our house was going to research solutions but we haven't heard back from him yet and he said if we learned anything to let him know and that he would look into it.

    I guess my question is can a professional hook an air exchanger/dehumidifier into the pre-existing duct work used by the air conditioner or will separate duct work need to be installed?, because that probably isn't an option. And do you recommend or anyone reading this recommend any specific air exchangers to use in this case? Thanks!

  4. #4
    Join Date
    Aug 2004
    North Richland Hills, Texas
    The fresh air supply can be tied into the supply ducts for your existing AC.
    A whole house dehumidifier/ventilator would need its own return from inside the house, and fresh air intake duct from outside the house.
    An ERV or HRV would need a stale air intake from inside, and individual fresh air intake, and stale air exhaust ducts to outside.

    I like the whole house dehumidifier/ventilator option because it gives you direct control of the humidity year round. In a relatively tight house it also keeps the house under a slightly positive pressure, so except during very windy conditions, almost all of the air coming into the house is through the ventilation system, where it gets filtered, etc..
    It is an expensive option though, and the fresh air ventilation alone would likely be all you need to keep the humidity down in the winter months.
    The dehumidifier comes into play mostly during the shoulder seasons, when it is humid, but not warm enough for AC, and during particularly humid times in the cooling season.

    The cheap and easy thing would be a fresh air intake ducted to the return on your AC, with a motorized damper, and a ventilation control to open the damper and run the system fan on a ventilation schedule, but it has the potential to cause as many problems as it solves.

    I'd recommend finding a contractor in your area that is actually capable of testing the house to determine your actual ventilation and dehumidification needs.
    This will involve performing infiltration testing with a blower door, and only a small percentage of contractors have that capability.

    I'm accustomed to dealing with a somewhat different climate than you are in, quite a bit different type of construction, and haven't evaluated your house, so can't really make specific recommendations for what you really need.
    If more government is the answer, then it's a really stupid question.

  5. #5
    Thank you so much, I'll definitely look into to that.

  6. #6
    Join Date
    Jun 2003
    Madison, WI/Cape Coral, FL
    Checkout the web site all the details about a ventilating whole house dehumidifier. The cost will be no more than an ERV with advantage beiing able to maintain <50%RH througout the warmer 3 seasons of the year.
    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"

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