Do You Really Need a Vapor Barrier in Your Crawl Space?

You may be thinking that installing a vapor barrier in your crawl space is unnecessary. After all, you don’t hardly ever even think about your crawl space, much less spend any time in there, so who cares if it’s smelly or damp down there? Isn’t the floor in between your living space and the crawl space enough?

We’re here to tell you that logic is all wrong. A vapor retarder, also commonly referred to as a vapor barrier, is actually pretty important. Like, super-duper important. In fact, having a vapor barrier in your crawl space should actually be the lowest standard for protecting your property, and there’s even more you can do.

Having an effective vapor barrier in your crawl space can help prevent damage, and therefore expensive repairs in your home. By going without this feature, you could be risking serious damage to your foundation.

What Is It, and Why Should I Have It?

Most often, a vapor barrier is found as a plastic sheet covering the crawl space floor, which is typically dirt. Its sole purpose is to stop moisture and chemical vapors that may be in the ground from rising up into the space under your house.

 There are two reasons you should care

  1. The crawl space supplies the air that is in your home. One study even estimated that up to 50% of the air you breathe on the ground floor of your house comes from your crawl space. If you or a family member in your home suffers from any respiratory complications, the quality of the air inside your home should be a big deal to you.
  2. Your house happens to be made up of porous materials. That means they allow for the circulation of air, and moisture as well. Moisture can wreak havoc on the health of your home. All that moisture in the air can foster an environment which is prime for the growth of mold, can increase the workload on your heating and cooling system, can accelerate the degradation of your floorboards, and can invite insect infestations.

How Should You Install a Vapor Barrier?

Generally, laying down a vapor barrier in your crawl space is a straightforward project. Luckily, this is something that most homeowners are able to tackle by themselves. First, you are going to want to know the area of your crawl space in square feet, so that you will have an idea about how much material you will need to buy. Your local hardware store should have a variety of options for you. 6 mm is the minimum thickness that we recommend, as it will prove to be more terrible than other materials, but up to 15 mm thick is ideal.

Make sure the crawl space is clear of trash or other debris before you start your project. After you have ensured an open space to work, carefully enroll the plastic sheet and lay it flat across the ground. You can use staples or heavy-duty construction tape to anchor it in place.

It should be noted that the typical vapor barrier won’t last forever. You can expect to have to replace it every 10 years or so. If the idea of crawling around in the crawl space under your home doesn’t exactly sound like fun, you can look for a contractor to do the work for you. For the price of around $1 per square foot, you should be able to find someone to install a vapor barrier in your crawl space.

What If Your Crawl Space Has Issues?

After the installation of your vapor barrier, you will instantly enjoy improved air quality in your home. The air will become less humid, smell fresher, and you may even notice a difference on your monthly energy bill.

 However, if you don’t notice any results, you may have other issues.

  • Standing Water : If you are experiencing accumulation of water under your house during heavy rains, you’ll need a waterproofing solution. The vapor barrier is only effective against the movement of moisture coming up from the ground. In the event of the accumulation of standing water in your crawl space, the vapor barrier will have a tendency to float on top of it, making it completely useless.
  • Failing Insulation: If you have fiberglass insulation in the crawl space and it is falling down, or if you tend to have very cold floors when the weather is cold outside, you might want to install spray foam insulation instead of simply using a vapor barrier. Spray foam is far superior to fiberglass and will last a lifetime, and can be used in conjunction with a vapor barrier.
  • Humidity: If you are experiencing extreme humidity in your home even after the installation of your vapor barrier, you might need to install a dehumidifier.
  • Mold:  You are going to need professional help in the event you discover mold in your crawl space. Some types of mold can be dangerous to remove, and you will need a contractor to help you remove it and diagnose its cause.