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  1. #1

    Default Basement ventilation system vs. dehumidifiers

    We have a 27 yr. old house - we are the original owners. It has a cinder block foundation - one side of foundation is underground and the other side is above (walk-out basement on one side). We have never had water in the basement and all leaders for the house have buried drainage "systems" carrying water away from the house. We have a problem with "musty" smell in the basement mostly in the summer/fall. Not much smell in the winter. Basement has one sliding door out the back, but no other windows. We recently had new energy efficient windows installed and all siding removed and Tyvek, Styrofoam insulating board, and then vinyl "shakes" installed. We want to get rid of the musty smell. Would you suggest a ventilation system such as Humidex or a dehumidifier? I don't want to have to empty a dehumidifier. Whole house has central air in summer, but ductwork for the first floor is in basement-hence when AC is on we are getting smell from the basement coming up through the first floor AC ducts. Any info anyone would have on ventilation systems for the basement would be very helpful.... Thank you! P.S. We have put waterproof paint (UGL) on all the basement walls - even though we had no problems with water in the basement or the walls. The basement is totally dry - but in the summer/fall, like I said, the musty smell is there in the basement....
    Last edited by homeowner123; 03-18-2008 at 07:29 PM. Reason: Added info

  2. #2
    Join Date
    Nov 2007
    Sand Springs, OK

    Default Re: Basement ventilation system vs. dehumidifiers

    I think the new ventilation systems are going to be less hassle than emptying a dehumidifier.

    I don't have any practical experience with either.

    I do have a friend in MD whose home is barely liveable because of the moisture and the dehumidifiers can barely keep up.

    I think I saw on Wasted last night that a family was saving about $200 a year by switching to a ventilation system instead of running the dehumidifiers but they had also switched from unvented gas heaters to electric which kept the unvented gas heaters from putting out 80 liters of moisture in their home every year.
    Debby in Oklahoma

  3. #3
    Join Date
    Aug 2007
    The Great White North

    Default Re: Basement ventilation system vs. dehumidifiers

    Interior ventilation of a home is always a challenge for controlling air quality Ö. whether itís for moisture , odors , etc..

    Taking steps for improving the tightness of the homeís envelope with sealing leaky areas , improved sealed windows , upgraded insulation , high efficiency direct vented heating systems Ö. while a good thing for comfort and efficiency Ö.. can actually create some variables that should also be addressed.

    Older leaky homes have one thing going for them Ö.. because they are leaky the air within the home gets exchanged. Stale moisture laden inside air will leak out through the openings and fresh outside air will infiltrate replacing the inside air that escaped. With older conventional heating equipment and even open fireplaces will use the inside air for the combustion and will be exhausted out through the chimney.

    With a high efficient heating systemÖ. one that uses a sealed combustion chamber Ö.. the fresh air for combustion is brought in directly from outside into the sealed chamber and the exhaust is directly vented outside Ö. no air from the house is used and exhausted from the interior.
    When a home is tightly sealed from air leakage Ö. generally inside air wouldnít escape and fresh outside air doesnít get in.

    So what does this all mean? ....

    Basically whether itís an older home that has been sealed or a new home that is tightly sealed there isnít as much air exchange that occurs. So all the interior air becomes stale and will increase in moisture because it becomes trapped within the home.
    Many times when people have tightly sealed their homes they experience an increased moisture issue Ö. usually shows in the colder season as condensation build up on the windows.
    This will require some sort of controlled form of mechanical air exchange and one method that works extremely well is an air to air exchanger or Heat Recovery Ventilator (HRV).

    Basements have there own unique challenges because they are below ground and generally cooler in temperature. Cooler air canít hold moisture as well as warm air Ö.. thatís one reason basements generally are more humid and clammy feeling.

    The basement will be surrounded by earth outside and there is moisture in that earth. Concrete is generally a porous material so moisture will penetrate through. With the pressure of the soil outside the moisture in the soil can be forced into the raw concrete by hydrostatic pressure. If the exterior walls of the foundation are properly sealed with proper waterproofing ( not damp proofing ) materials along with proper drainage the moisture in the basement will be greatly reduced.

    Typically basements donít have much mechanical ventilation and generally arenít included into the return ducting for HVAC equipment. So this air remains cool and stagnate Ö.. because it remains cool it wonít hold moisture in the air very well and becomes clammy.

    A dehumidifier can be an effective way to reduce this humidity and typically the bucket can be removed with a provision to attach a hose to them for draining into a floor drain Ö.. for example.

    Opening windows in the basement during moderate seasons will also help by exchanging the air inside the basement.

    Another method is to include a couple of strategically placed cold air returns for the A/C in the basement. This can be an advantage since the A/C is basically a large dehumidifier.

    Or mechanical ventilation could be used to exchange the air within the basement.

    Sorry for the long winded post ... just one of those moods.

    Hope this makes sense and helps.

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