The Truth About Crawlspaces and What To Do About Them

The Truth About Crawlspaces and What To Do About Them

Checking crawlspaces is not the most enjoyable part of a home inspection, but they must be looked at because your crawlspace reveals a lot about the health of your home.

Actually, most people don’t pay a whole lot of attention to their crawlspaces. Why? Well, they are dirty, difficult to navigate, and usually inhabited by a lot of spiders and other creepy crawlies. Who wants to think about that? Hopefully you will after reading on for a few minutes.

When I ask people how much they know about their crawlspaces, they usually tell me that they are dark, dirty, musty ugly places. This is all true, but that is not the whole story.

So, what is the truth about crawlspaces?

Thanks in part to some of the ideas from author Lawrence Janesky, this article will clear up some crawlspace misconceptions, and what to do about them for your comfort and healthy living.

Most crawlspaces have a dirt floor, which is actually exposed earth beneath your home. This earth is cool & damp; therefore, it creates to a lot of water vapor within the crawlspace. Moisture also seeps in through openings, cracks and leaks in the foundation wall, further contributing to a wet crawlspace. Water can even come in under the footings or slowly seep through concrete block walls because they are porous. Essentially, moisture will make its way in as long as there is an opening.

This moisture from the earth floor evaporates. The water from leakage will puddle and slowly evaporate.  Through vapor diffusion, moisture moves up into the home. This is a continuous cycle.

The reason it is so bad for the home is a combination of relative humidity and vapor diffusion.  Simply put, when the air is heated or cooled, the amount of moisture in the air changes.  Warm air holds more moisture than cold air.

In the summer, when the temperature in the crawlspace is cooler than outside, and this warm air vents into the cool crawlspace, the air turns into water vapor (because cold air hold less moisture). At this point, condensation is created, making everything wet, causing wood rot, mold, increased energy costs, while attracting pests. (FYI – One dead giveaway that your crawlspace is damp is the presence of spiders. They like cool damp places)

Here is another truth about crawlspaces. Most crawlspaces are vented because it was first thought that a vent would help move the moisture (from the crawlspace ground) out of the home. It has been proven that this thinking is actually flawed.

In fact, when it rains outside, or when it is a damp day, moisture is actually venting into the crawlspace. On a hot day, as mentioned above -this warm air will come into the crawlspace, mix with the cold air and flow up into the home. In the end we have created moisture problems within the home.

With wood, the more wet it gets the more it rots and the more mold grows. Even if after a hot summer day cools down for the next few days, the original moisture still remains in the crawlspace. This moisture will rust metal duct work, rot the wood structure and diffuse into the home. So in theory, venting your crawlspace doesn’t work because it actually attracts moisture to your crawlspace.

In the winter, a vented crawlspace will bring the cool air into this area. When this air mixes with the damp floor, the humidity does not really increase that much, but it makes the air cool, which can lead to frozen pipes, cold floors and higher energy costs.

The air quality in the crawlspace is not very healthy because it contains mold spores, and other nasty gases. When air mixes, and rises through small holes around the duct and other spaces, it eventually makes its way up into your home. This should concern you.

Some of the more common effects on your home and health may include:

  • Increased allergy and asthma conditions
  • Condensation, rot and mold in the attic
  • Increased cooling and heating bills
  • Sticking of doors and windows

We know that moisture accumulates in the crawlspace and that it is bad for our home and health…what can we do about them?

1)   First of all, you will have to address any water leakage by installing a sump pump to remove the water. If there is serious flooding you will need to improve the drainage system.

2)   Next, insulate the crawlspace walls, with rigid foam insulation (Blue or Pink boards), or spray foam. Do not use the fiberglass batts because they absorb moisture and allow air movement.

3)   Now, provide a perfect seal by separating the home from the earth. This can be done with a concrete floor over a plastic vapor barrier. If you already have a concrete floor, it is best to install the sump pump at the lowest point of the floor. Alternatively, you can install a heavy-duty (20 mil) plastic liner over the dirt floor. The liner must be thick, robust and continuous. It must completely cover the floors and on up to the top of the crawlspace walls.

4)   Finally, you can seal the vents with gasket vent covers, and all areas where moisture can enter. Theses areas include: around duct vents, under sill plates, hatch doors or other openings you see.

These steps will help you maintain a healthier, stronger and less expensive home over the long run. For best results, a company that specializes in basements and crawlspaces should perform this work. If you have any comments or questions, I’d be happy to point you in the right direction. Good luck with turning your crawlspace into a happy space.