Why You Need a Vapor Barrier

Vapor barriers are materials commonly installed in buildings to reduce summer heat gain and winter heat loss. A vapor barrier serves as your front line soldier in your humidity battle. It acts like a space suit. It reflects the evaporation of heat from the earth. This makes your crawl space stay cooler. If your crawl space stays cooler, chances are, mold and mildew problem will be avoided.

In addition to a vapor barrier in crawlspace which primarily serves as a vapor retarder covering the ground, your crawl spaces should have an adequate natural ventilation to facilitate better air movement throughout the space. The math behind this is, if a vapor retarder is present in the crawl space, 1 square foot of free vent area is required for every 1,500 square feet of crawl space ground area. Without a barrier present, 1 square foot of free vent area is required for every 150 square feet of crawl space ground area.

Bottom line is, though a vapor barrier proves to be excellent in battling humidity concerns, more often than not, it’s not enough. It only serves as your first aid kit. It will continuously be put to the test by insects and small animals which along with molds and mildew are protagonists of your family’s health. It needs a much potent ally to be victorious on the humidity and moisture war. In most cases, crawl space vents include louvers and/or screens to prevent the entry of insects and small animals. These extra protections however have their downsides. Coverings slow air circulation and cut down on the vent’s effectiveness. To compensate for this underperformance, you will need to double the amount of ventilation.

How a Crawl Space Dehumidifier Can Solve Your Problem

To solve all these hassles, a much skilled soldier comes to the rescue. You’re right. I am referring to a dehumidifier for crawl space. Along with your vapor barrier, they will form a dynamic duo to protect your home against mold and mildew. With a vapor barrier doing the initial touch, your crawl space vapor dehumidifier will do the remaining tasks. It completely isolates your home from the earth and dramatically reduces the humidity level in the air. Lower humidity levels reduce or, occasionally, eliminate mold growth, rot, and critters from your crawl space, making the entire house healthier.

As an added advantage, crawl space dehumidifiers commonly have built-in intelligence that allows it to be able to detect the level of dampness and also the frost. Their hot air inbuilt system functions well in defrosting.

Though you may be disappointed with the idea that you can’t fit under the crawl space to blow the air from time to time, there’s nothing to worry about after all. You just need to have the tandem of vapor barrier in crawl space and, of course, a dehumidifier for crawl space for maximum protection against unwanted guests like molds and mildew.

We found several solutions to this problem.  Click the diagram on the right to see the ideal positioning of the moisture barrier.

Here is a vapor barrier movie showing you how to stake down the plastic sheeting.  Notice, his moisture barrier does not go up the sides of the wall.   You will observe that in the video the vapor barrier only goes to the edge of the wall, while the picture shows the polyethylene being attached several feet up the wall.  Depending on your particular crawlspace and personal preferences, you can do it either way.  If you choose to go further up the wall however, be sure the wall is dry before attaching the plastic sheeting and be sure not to attach it to wood posts or studs because moisture will become trapped and then you have the potential for wood rot.

If needed, run your Dri-Crawlspace Dehumidifier^® for a day or two to dry out the walls and surfaces before attempting to use tape or adhesives on the crawlspace walls.

The seams in your vapor barrier should overlap by 6 inches and be sealed with builder’s tape or construction adhesive to form an airtight barrier.  You can seal the edges of the vapor barrier to the foundation walls with construction adhesive.  When it is completed, weigh down your vapor barrier with sand or stones to help prevent ground moisture from escaping into the crawlspace and to help protect the polyethylene from tearing when walking on it.