What Is A Vapor Barrier in Construction? Types Of Vapor Barriers Materials

What Is A Vapor Barrier in Construction? Types Of Vapor Barriers Materials

What Is A Vapor Barrier in Construction?

A vapor barrier is a material used to prevent moisture from passing through walls, ceilings, and floors in buildings. This barrier can come in the form of a sheet or liquid-applied coating that acts as an air and moisture barrier.

Vapor barriers help keep water vapor from entering the building envelope, which reduces the risk of condensation forming and leading to mold growth within walls and other enclosed spaces.

They are critical components of any energy-efficient construction project, allowing for more consistent indoor temperatures with less humidity.

There are several types of materials that can be used as vapor barriers, including mechanically fastened sheets, adhesive membranes, fluid-applied materials, insulating board stock and medium-density spray polyurethane foam.

The effectiveness of a material as a vapor barrier depends on its thickness.

A vapor barrier is a material used to prevent the passage of water vapor through a surface or structure. There are various materials that can be used as vapor barriers, including plastic, aluminum and even paint.

The effectiveness of a vapor barrier is often measured by its permeability, which refers to the amount of water vapor that can pass through the material. In selecting a vapor barrier it is important to consider the climate in which it will be used as different materials may be more or less suitable for different environments.

Types Of Vapor Barriers Materials

There are several different materials that have been used as vapor barriers in construction: polyethylene film, Kraft paper, aluminum foil, insulations like expanded and extruded polystyrene board and foamed-in-place insulation, and vinyl wallpaper.

Polyethylene film is the most common type used because it is inexpensive and easy to install, but it can deteriorate quickly if exposed to the sun and is prone to punctures.

Kraft paper, often found on older homes, can act as a limited vapor barrier when it is glued to fiberglass or mineral wool insulation batts. Aluminum foil, originally intended as a radiant barrier, can also serve as a vapor barrier when installed on batt insulation.

Insulations like expanded and extruded polystyrene board and foamed-in-place insulation can act as vapor barriers if they are thick enough. Finally, vinyl wallpaper can also serve as a vapor barrier, although it is not recommended for use in hot climates. Vapor barriers are typically installed on the exterior of the wall system in hot areas.

Benefits Of Installing A Vapor Barrier

Installing a vapor barrier in a crawl space can provide numerous benefits for homeowners. It can help prevent moisture from entering the home through the flooring, which can lead to mold and mildew growth and potentially cause structural wood rot.

A vapor barrier can also deter pests that thrive in damp environments, protect wiring from moisture or rust, increase energy efficiency through added insulation, and make it easier to access the crawl space. Overall, it is a cost-effective solution to prevent problems that can occur if moisture is not properly controlled in the crawl space.

Drawbacks Of Installing A Vapor Barrier

The use of vapor barriers, also known as vapor diffusion retarders (VDRs), was originally intended to prevent walls and ceilings from getting wet. However, it has been found that when VDRs are installed on the inside of an assembly, they can also prevent inward drying, which can lead to moisture problems and mold.

This is especially true in below-grade spaces and when using complex wall systems. The effectiveness of VDRs can also vary depending on the climate, as most research on their use has been conducted in cold climates and has not considered how they impact vapor flow in other climates or during the summer months when air conditioning is in use.

In these cases, moisture from the exterior environment may flow into the wall system and cause condensation on the cooled interior VDR, especially if a low-perm poly material is used. The use of certain claddings, such as brick and traditional stucco, can also impact vapor flow and add unwanted moisture to the assembly, especially in hot and humid weather.

To address these issues, it is recommended to vent masonry claddings and use higher-perm products like paint as VDRs to allow the wall system to cycle with the seasons.


In conclusion, a vapor barrier is an important part of any home’s construction and maintenance. Without it, excessive water vapor can cause damage to the structure of your home as well as potentially lead to mould growth and other health issues from the excess moisture.

There are many different types of vapor barriers available, so make sure to do research when selecting one for your home. With the right type of vapor barrier properly installed, you can help keep your home safe and comfortable for years to come.

Related Posts

error: Content is protected !!