The Blog

Winter Rains and Vapor Barriers: Why Crawl Space Conditions are Critical in Winter

By Mike on October 30, 2015

Washington is a very wet state. While we don’t rank high in how much rain we get, the rain that falls lasts a long time in the form of groundwater and moisture in our air. Winter is especially a season packed with cloudy skies and wet weather.


The effects of this wet winter weather can be disastrous in homes that are not ready to face these conditions. Flooding, wood rot, mold and mildew growth, and animal infestations are common in homes that are unprepared for damp winters. While there are several steps that homeowners can take to prepare their homes, few of these projects are as significant as installing a vapor barrier in the crawl space.

Purpose of the Vapor Barrier

The vapor barrier addresses a major problem in crawl spaces that have dirt, gravel, or sand floors. The wet conditions outside produce extremely wet soil. The moisture in the soil then evaporates into the crawl space through the exposed ground. This dynamic creates a number of other serious problems:

1. High Humidity

Balanced humidity levels are critical to maintaining safe crawl space conditions. Without a vapor barrier, moisture is allowed to freely evaporate and increase the percentage of water in the air. This simple mistake produces a host of other negative consequences.

2. Moisture and Condensation

As the crawl space gradually becomes more and more humid, the moisture in the air will begin to condense. The contrasting indoor and outdoor temperatures cause the water in the air to condense and form thousands of tiny water droplets. While the inside of your home may feel nice and dry, the crawl space is just as wet as the winter weather outside.

3. Mold and Mildew


Wet crawl space conditions are ideal for mold and mildew growth. A warm space with plenty of water causes the rapid growth of mold and mildew colonies along the walls, floors, and insulation. These colonies can release mold spores into the air, which then become airborne and are carried up into the home. A shocking amount of the air in your home is actually pulled directly up from the crawl space, so if the air in your crawl space is full of wet, moldy, musty air, your home will be full of the same smelly, low-quality air.

4. Wood Rot

In the same way that mold and mildew spread in wet crawl space conditions, so can wood rot. These wet conditions encourage various types of fungi to attack the wooden beams, supports, and the frame of your home. If the situation is not properly addressed, this rot can threaten the integrity of your home and reduce its value.

5. Damaged Insulation

In order to function properly, insulation must be kept in a dry environment. When exposed to high humidity levels, water, mold, mildew, and wood rot, crawl space insulation quickly loses its ability to function properly.


Insulation is comprised of thousands of tiny air pockets. These pockets trap the air in the crawl space and prevent the transfer of energy. If these pockets become full of water, or if the insulation starts to decay from the mold or mildew growth, then it cannot properly serve your home. In order to be restored, the crawl space insulation must be replaced.

All of these problems can be completely avoided by installing a vapor barrier in your crawl space. This resource will help to block the evaporation of water into the crawl space, thus protecting your home and insulation from harm.

Vapor Barrier Installation

In order to prepare your home to resist the winter weather, a thick, sturdy vapor barrier must be properly installed across the floor of your crawl space. Any old tarp won’t do since water can still evaporate up around the edges.

In order to properly install a vapor barrier in your crawl space, you must utilize the proper materials, installation techniques, and equipment to ensure an effective barrier is in place. A crawl space cleaning company like Clean Crawls can assist you in installing a vapor barrier in your home. For more information about our crawl space vapor barrier installations, contact us today by giving us a call at (866)-610-0098 or filling out our contact form.


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