Vapor barrier installation work in crawl space by Water Extraction Experts

Crawl Space Vapor Barrier and Moisture Intrusion Prevention

What is a Vapor Barrier?

A vapor barrier reduces the rate at which water vapor, such as humidity, can move through a material. The name eludes to how the material slows the movement of water vapor, and not completely halting the process. Vapor barrier implied the material would stop movement of the moisture hence the recent name change. The installation of a vapor barrier occurs during the crawl space encapsulation process. Encapsulation encloses and seals the space to prevent moisture from reoccuring inside the crawl space.

There are three classes of water vapor barriers, split into each class by the permeability of the material into a unit of perms. Class 1 is .1 perms or less and includes glass, sheet metal, polyethylene sheet, or rubber membrane. Class 2 is more than .1 perms but less than or equal to 1.0 perms. Materials in class 2 include unfaced expanded or extruded polystyrene, 30-pound asphalt coated paper, plywood, or bitumen coated kraft paper. Class 3 has the highest amount of permeability, more than 1.0 perms but less than or equal to 10 perms. Gypsum board, unfaced fiberglass insulation, cellulose insulation, board lumber, concrete block, brick, 15-pound asphalt coated paper, and house wrap all fall into class 3. Many new building codes require applying these materials under wall board to prevent vapor diffusion from bringing moisture into structural assemblies.

The climate and construction of your home determines how, where, and if you need a vapor diffusion barrier in your home. For existing homes, installing these can be difficult unless the home is undergoing extensive remodeling. Specialty paints are available for existing homes in colder climates.

For new homes under construction in a mild climate, painted gypsum wallboard and plaster wall coatings may impede moisture diffusion. Higher perm vapor barriers are recommended for new homes in more extreme climates.

How a Vapor Barrier Helps Your Home

Air Quality in Your Home

Your crawl space provides 40 percent of the air in your home. Without a vapor barrier in place, mold and mildew can form. These microscopic organisms can affect the air quality in your home, including causing health issues such as allergies and other respiratory issues. Along with health issues, subfloors could warp and other wood in the home may rot, as the floor in most crawl spaces is dirt or soil which allows all kinds of moisture to enter. Likewise, a vapor barrier can deter pests like insects and rodents from moving into the crawl space.

Temperature and Humidity Levels

The vapor barrier also keeps the temperature and humidity levels below the floor stable, thus protecting pipes from freezing and bursting in cold temperatures.


Common Moisture Related Problems

In northern parts of the United States, moisture vapor issues in the home are mostly caused by high indoor relative humidity levels, coupled with the low outdoor temperatures during winter months. Common moisture related problems include structural wood decay, expansive soil, metal corrosion, ice dams, and mold growth.

Here is a quick demo, from YouTuber Steve Maxwell, on what a vapor barrier looks like and how it functions to protect you.

Vapor Diffusion Barrier Inspection

During an inspection, we are looking for signs of water intrusion or high moisture content. These signs can include stains, rust damage on structural steel, mold or mildew, rotting wood, and water stains on the vapor barrier itself. Missing, loose or improperly installed insulation or vapor barrier is considered defective during an inspection. Framing, ductwork, piping, and wiring are also checked during the inspection for any defects.

Let us Inspect Your Crawl Space

While there are several ways a vapor barrier can be installed in a crawl space, only one way is the correct way. If your home was recently built, or had a vapor barrier installed by a previous owner, it could have easily been incorrectly installed. Mold and mildew can form on walls and ceilings with an improperly installed barrier.

Our team at Water Extraction Experts can provide a crawl space inspection, checking the area for moisture and mold issues and working with you to create a solution. With years of experience among our team, our goal is to bring you peace of mind and ensure the best results.


We service the following locations:

Colorado cities of Fort Collins, Loveland and Greeley, call us at 970-581-4498.

Wyoming cities of Laramie and Cheyenne, call us at 970-581-4498.

Albuquerque, New Mexico, call us at 505-250-6500.