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Community and Q&A

Airtight home – fresh air? Dehumidifier?

Kurt White | Posted in Green Building Techniques on

We recently built a lake house with foam insulation. This was my builders first foam house. the house has high humidity of around 56%. The wood floors have started to buckle in several area. I’m being told we need to install a dehumidifier but I’m also concerned about the lack of fresh air. My question is will a dehumidifier be enough or will I need to install additional equipment to balance fresh air into the house? I’m looking for advise before giving approval.

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    It's always a good idea to tell us your location or Climate Zone. That helps us provide good advice.

    Your first step should not be to install a dehumidifer. Your first step should be to verify whether you house has a ventilation system (for example, an HRV, an ERV, an exhaust-only ventilation system, or a central-fan-integrated supply ventilation system).

    Every tight home needs some type of ventilation system. Here is a link to an article that explains all of your options: Designing a Good Ventilation System.

    Here is a link to an article that discusses the causes of high indoor humidity (RH) levels, and ways to lower those high levels: Preventing Water Entry Into a Home.

    As a stop-gap measure, you should turn on one of your bathroom exhaust fans and let it run continuously, 24/7, for a few days. My guess is that this will lower your indoor humidity levels. It's not a permanent solution, but it will get you started.

    If you have a high-quality bath fan (like a Panasonic fan), you could install a timer on the fan, turning the exhaust fan into an exhaust-only ventilation system.

  2. Kurt White | | #2

    Thanks Martin

    The house is located an hour east of Dallas, TX. Quick question. Do you think installing an ERV would help both my air balancing and humidity issues?

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Q. "Do you think installing an ERV would help both my air balancing and humidity issues?"

    A. If you install an ERV and operate the ERV during cold weather, then the ERV will help lower your indoor humidity level.

    In the Dallas, Texas, area, however, operating a ventilation system during the summer will tend to raise the indoor humidity level (because the outdoor air in Texas is hot and humid during the summer). You still may want to operate your ventilation system, because people need a little fresh air, but don't expect your ventilation system to lower your indoor humidity level during the summer.

    The way to lower your indoor humidity level during the summer is to operate your air conditioner.

    Concerning the rest of your question -- what you call your "air balancing issue" -- I have no idea what you mean. Please explain what your "air balancing issue" is.

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