Vapor Barriers

Vapor Barriers are a very critical part of the building envelope. As we cannot see the vapor barrier, it is easy to forget the crucial role it plays in maintaining interior comfort. Read on to discover the properties of vapor barriers, how they help us and their installation details.

What is a Vapor Barrier?

A vapor barrier is a membrane that prevents the moisture in the air outside from reaching the building's interior space. It acts in association with the insulation to create a moisture-proof envelope.

What does a Vapor Barrier do?

Vapor barriers are used to achieve certain functions:

• Water can move through a building structure from where the air is moist and warm to the colder air. When the moisture hits cold air, it condenses. This condensation can seriously damage the structure. So the vapor barrier is needed to prevent this moisture from crossing over to the cold side of the structure. Learn more about condensation in the building.
• The vapor barrier also reduces air leakage. This doesnot reduce air leakage through wall openings like windows and doors.
• In homes where humidifyiers are used, vapor barriers can greatly enhance the effectiveness of the humidifyier but blocking the internal moisture from flowing out of the building.

Where the vapor barrier needs to be installed?

As is evident from its functions, the vapor barrier needs to be installed on the warm side of the building envelope to be effective. This is suitable for areas where the winter is the dominant season and it gets extremely cold. In hot and humid areas, the vapor barrier is usually not needed.

Read more about what the vapor barrier can do and the conditions where it needs to be installed.

What are the different types of vapor barriers?

The most common material used as a vapor barrier is polyethylene plastic film. Other vapor barriers are also attached to batt or blanket insulation. Read about the various types of vapor barriers and their advantages and limitations.

Details

Here is a typical detail for air/vapor barrier details

Next time, the discussion will focus on Metal Cladding. So see you then.

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The copyright of the article Vapor Barriers in Building Construction is owned by Shefali Kumar. Permission to republish Vapor Barriers in print or online must be granted by the author in writing.

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