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The Importance of a Vapor Barrier in Renovation & New Construction

August 22, 2017

Moisture moves all the time. Whether you are in an older home that you are remodeling, or building a brand new home from scratch, moisture management needs to be on your checklist of “Things to Do.” In the “Rules of Building Performance” from Construction Instruction, Rule #2 is that moisture moves from warm to cold, followed by Rule #3, that moisture moves from more to less. The concept to remember here is that moisture is always moving.

Thankfully, the solution to this is known as a vapor barrier. Vapor barriers keep moisture away from the building material you are trying to keep dry.  Building materials are going to wick moisture, some more than others, but all will to some extent. By keeping your building materials dry, you prolong their life and maintain the efficiency of the task you installed them to do.

What IS a Vapor Barrier
The type of vapor barrier required for your specific project will be determined by your local building code. A widely accepted vapor barrier is a sheet of 6-mil polyethylene that you place before applying the building product you are installing.

In the example below, you can see the 6-mil poly has been placed under the EPS rigid foam insulation providing a barrier from the earth below.


While Plasti-Fab EPS is a closed cell insulation, a vapor barrier is still recommended based on local building codes to protect it from the elements. Let’s look at a few installation examples using Plasti-Fab’s EPS Insulation.

Insulating Exterior Foundations
Continuous insulation applied to the exterior of foundation walls reduces
expansion and contraction concrete foundation walls would be subject to
due to temperature differences between the interior heated space and the
exterior air/soil. Learn how to install exterior foundation insulation

Insulating Above a Concrete Floor
Insulating your basement floor provides added comfort and increased
energy savings. Learn how to install insulation above your basement floor

Insulating Below a Concrete Slab
Continuous insulation under your slab eliminates thermal bridging,
increasing your total effective RSI/R-value. This reduces energy costs and
increases your energy savings. Learn how to install insulation under a basement floor

underslab high compressive

Commercial and Residential Applications
Vapor barriers are important in both residential and commercial applications as R-value and insulation is important for any structure. You can learn about the commercial applications in our Commercial Solutions section.

What Did We Learn
While moisture is present in in every facet of building science, it is manageable through the use of properly installed vapor barriers, therefore protecting your home, business or commercial investment for years to come.

Do you have more questions regarding this topic? Contact us today in the ASK US section of our web site, and we would be happy to help!



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