Opening and closing the crawlspace vents and understanding moisture control is one of the most conufusing topics for homeowners. So, what should you do when you need information? Google it! Well I’ve done this I can see how it could get very confusing. There are too many opinions and some are too technical to understand. So we need some simplified tips.

Why is Precision Comfort Systems interested in this? As your Indianapolis area comfort specialists (serving all of Central Indiana) we are expected to control the humidity in our customer’s homes. You need a source that understands moisture science. Here are some important clarifications.

  • First and most important… liquid water is different than water vapor. If any part of your home has liquid water problems, you need some help from experts in drainage, plumbing, pumping, water proofing and maybe all of the above. Fix all liquid problems first! Then you can read the rest of this post.
  • Next, if you have air conditioning and if any part of your cooling system is in the crawlspace, you have even more reason to understand moisture. If you live in a humid summer climate, you cannot allow humid air to come in contact with your cooled surfaces. This will cause condensation and voila… now you have a liquid water problem.
  • Here is the simplest way I know to help you understand  and visualize what to do with your crawlspace: TREAT YOUR CRAWLSPACE AS A CONDITIONED BASEMENT. By “conditioned” I mean heated, cooled, dehumidified, insulated and closed off from the outside. Treat this area under your home just as you would treat an extravagant basement entertainment room in a luxury home. Would you open a window to this area on a hot summer day and expect to stay comfortable? No. The outside air is the source of moisture in the summer.
  • A legitimate question is: “So why does my crawlspace have vents? I close them in winter and now you suggest I close them in the summer.” The answer is, crawlspace venting is a leftover design from a time with little air conditioning or perhaps a design borrowed from a drier climate. In fact, even in Central Indiana we do have a few summer days that could be considered drying days and then a little fresh air could benefit this area. But most summer days have enough moisture in the air that as soon as it passes into the cool crawlspace, the air temperature decreases, the moisture content is now closer to 100% saturation and much of the masonary and wood surfaces in your crawlspace are cool enough to condense the water vapor to liquid.
  • And then you turn on the AC to help comfort your home and your problems increase by creating very cold AC system parts. After a few days of continuous condensation your basement may look and smell like Open crawlspace vents can cause moisture problems in humid midwest climatesthis…

I could go into more science on specific humidity, dew point, wet bulb temperature, etc., but the above is really all you need to know. Close and seal the vents in your crawlspace walls. Condition the crawlspace area as if it were a short little basement entertainment area. You may need to add a dehumidifier to help out the air conditioner. I go into more about solutions in the next blog entry: Damp Crawlspace or Basement Solutions.