What Exactly Is a Vapor Barrier and What Does It Do?

Most homeowners are at least somewhat familiar with insulation, like the kind that goes in your attic. But not nearly as many know about vapor barriers, which are most commonly installed in a home’s crawl space. For that reason, we’re going to break down exactly what a vapor barrier does, how it works, and why your home might just need one installed.

What Is a Vapor Barrier?

A vapor barrier is a material that helps to prevent vapor from diffusing through building materials. In general, moisture will always flow from an area with a higher concentration to a space with a lower concentration. This functions in the same way that heat spreads out or disperses from hotter areas to cooler areas.

If that sounded a little too technical, you’re not alone. Vapor isn’t nearly as readily understood by the general population, so we’re going to break it down even further.

Think of it this way: When there’s moisture in the air, as the air travels the moisture goes right along with it. If you have moist (humid) air traveling through your home, then it can get into the building materials and cause problems.

If too much moisture dampens the wood in your house, it can begin to rot, especially in areas near the ground like a crawl space. Damp areas are also breeding grounds for bacteria, mold, and mildew. A vapor barrier can be the first line of protection against letting this moisture move through your home in the first place.

What Does a Vapor Barrier Do?

In order to stop the moist air from moving up through the structure of your home from lower areas like the crawl space, it’s necessary to set up a defense. One of the best ways to do this is by installing a vapor barrier.

As you may have guessed by now, a vapor barrier does the job of keeping moist air from passing through your home’s structural surfaces, such as wooden beams. It might seem simple, but a high-quality vapor barrier can actually save your home from damage and even make your house more energy efficient in the long run by reducing overall humidity.

But that’s not all it does. Vapor barriers wear a lot of hats, including:

  • Preventing your flooring from water damage
  • Stopping mold in its tracks by limiting damp environments
  • Reducing soil gases, such as radon or methane
  • Providing higher quality air inside the home

Traditionally, vapor barriers are used in crawl spaces, but they can be utilized in other areas as well like the attic. Attic insulation goes a long way toward making your home more efficient. But a vapor barrier can actually work alongside it for even better efficiency and overall home health.

What Is an Acceptable Amount of Crawl Space Moisture?

If you don’t currently have a vapor barrier installed, then you may be wondering what the fuss is all about. Or, put another way, you may be asking yourself whether the amount of moisture you have in your crawl space now is enough to even justify getting a vapor barrier.

This is a fantastic question. Here’s the short answer: Generally speaking, you want to keep your crawl space humidity level to no more than 60%. A good rule of thumb is within the 50% to 60% range: under 60% to prevent mold, and over 50% to prevent drying out the wood. With all that in mind, 55% is an ideal humidity level for your crawl space.

If you’re already within or close to that level, then it might seem like you don’t need a vapor barrier at all. But, as mentioned earlier, the truth is that vapor barriers do so much more than lower humidity in your crawl space. They can keep moisture of all kinds from traveling through the structure of your home.

How to Install a Vapor Barrier

If you’ve determined that you need a vapor barrier in your crawl space, then you might be considering installing it yourself. While we certainly applaud your ambition, as a rule vapor barriers are not a great DIY project.

Not only is it a very tricky task due to the confined area of a crawl space, but it also requires a number of tools and materials that most people don’t have lying around the garage:

  • Rigid insulation
  • 6 Mil plastic
  • Caulk and caulking gun
  • Fabric landscaping stakes
  • Treated 1×4 lumber

And that’s just the beginning. The knowhow to use those tools for a vapor barrier installation is another thing entirely.

Crawl spaces are notoriously cramped and difficult to navigate. So, if you find yourself in need of assistance during your installation, then you could be putting yourself in danger, potentially resulting in bodily harm or injury.

The point is this: Vapor barrier installations should nearly always be done by a trained professional with the right skills, experience, and tools to get the job done safely and efficiently.

Do You Need a Vapor Barrier Installed?

Depending on the structure and location of your house, you may need to consider having a vapor barrier installed. The most likely spot is in your crawl space, but your attic could also benefit a vapor barrier installation. If you’re curious about the process and whether your home needs an upgrade in the basement, get in touch. We’re here to answer any questions you may have and set your mind at ease. Give us a call or an email today to get started and get a free quote.

Attic Insulation Saves the Day

No matter where you live, your house needs insulation. In fact, few areas of the home need it quite as much as the attic. With great attic insulation, you can keep your home energy efficient, maintain the right temperature, lower outdoor sound, and save on your energy bill each month. If you’re curious about whether this could work for you and your home, just give us a call or shoot us an email. We’re here and ready to answer any questions you may have.