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Latest News How to Install a Crawl Space Vapor Barrier And Prevent Pests
How to Install a Crawl Space Vapor Barrier And Prevent Pests

How to Install a Crawl Space Vapor Barrier And Prevent Pests

If you are outlining your plans to install a crawl space vapor barrier in your home, you’ve reviewed the project’s reason and importance. But maybe you still have a few unanswered questions.

If you are installing crawl space insulation on your own or hiring a professional, it’s crucial to follow specific building codes. There is a wealth of information on the Department of Energy website.


Stop Moisture From Infiltrating Your Home

The best way to stop moisture from infiltrating your home is to install a durable crawl space vapor retarder that covers the dirt floor and walls. A vapor retarder will prevent the evaporation of ground moisture into the crawl space. It will also prevent mold from forming in your crawls space. If combined with a drainage system, the result is a dry and more energy-efficient home.

Pests love moisture. When it is dark and damp, your crawl space invites all bugs types that can infest your home. Some seem innocent enough, but termites are a big deal. A vapor retarder is just that; it pushes back on odors and acts as a moisture barrier. If you can repel the moisture, then pests are less likely to penetrate your home.

One other reason for installing a vapor retarder is to reduce the amount of radon gas that may leach out of the ground and seep into your home. Radon is present everywhere in the United States, but the concentration will vary from state to state.

 

Select The Right Material

Selecting the right product is essential. You will spend money, time, and effort making this installation and will not want to repeat. Plain polyethylene will likely deteriorate in a short amount of time due to its recycled content and inferior polymer.

You will want to select/purchase durable, preferably a reinforced polyethylene sheeting. White would be the best color for many reasons. If you have to work in your crawl space or if it doubles as extra storage, white will make it brighter and easier to see in the area covered.

If you currently have any standing water in the crawl space, you want to find the source and remedy. If it’s a constant or inevitable flow or drip, you should figure out how to divert the flow. You may have to dig a small trench and use a diversion pipe.

Building codes use to require ventilation in your crawl space. The thought was that the air flowing through would dry the area. Depending on the RH (relative humidity) level, that will probably never happen. Crawl spaces will always be cooler unless you live in a freezing area, spring and summer will bring warmer air. Combine the warmer air with the cold air under your house or your crawl space area, and you will see condensation.

Ideally, it would be best if you closed up all vents when encapsulating the crawl space. Once done, you should be able to dry out this area. You want to lay out your vapor retarder making sure you overlap the plastic by at least 6 inches (and taping well). You will run the plastic up the walls sealing any overlap of material. There are several methods used to attach the fabric to your foundation.

There are three types of conventional concrete foundations: poured concrete, concrete block and post, and pier (Older homes used to rest on just the pier, but that has been phased out in favor of foundation methods with greater integrity). Building codes regulate the size and acceptable types.



Getting Started

It would be best if you made a checklist to be sure you’ve addressed any problem areas in your crawlspace. You will be covering any cracks where moisture could enter the area and keep the pests out. Next, you will be selecting your vapor retarder material.

You will want to remove any debris, rocks, and other rough items, anything that doesn’t need to be under your vapor retarder that might cause tears/damage.

Installation is typically a two-person job, mostly to make it easier, especially if you have to install around items such as pumps, ventilation equipment, drain pipes, etc. Having the extra help will allow for a smooth rollout of the large rolls of vapor retarder.

You will need seaming tape to use when overlapping the material. Depending on the type of walls, you may also need tacking materials. You will run your vapor retarder up the wall to cover all air gaps/cracks.

You could attach tack strips around all the walls, and then you will attach the vapor retarder to the strips then secure with seaming tape. You will want to go up as high as you can on the wall covering all openings.

You might leave a 6-inch gap minimum between the top of the vapor retarder and the bottom of the floor. This should appease the exterminator (if you were concerned about venting guidelines).


Reef Industries’Griffolyn® vapor barriers and vapor retarders can prevent water vapor from causing poor insulation performance, structural damage, and other moisture-related problems. The main reason for retarding water vapor transmission through the building envelope is to prevent water vapor from condensing within the building structure cavities. The Griffolyn® polyethylene vapor retarder system’s low permanence keeps moisture from infiltrating the building envelope.