Vapor Barrier Off Gassing: What You Need to Know

vapor barrier off gassing

Vapor Barrier Off Gassing: What You Need to Know

A common question we get asked is whether our vapor barriers off gas. In order to answer that question, let’s take a step backward and first talk about what off gassing is and why it can be harmful in your home.

Here’s what you need to know about vapor barrier off gassing.

To date, there has been very little science or testing done by manufacturers or private labs in regards to vapor barriers off gassing. The best information gathered has been from the few vapor barrier manufacturers that have made an investment in private and internal testing, longtime installers, contractors, and homeowners.

What is off gassing?


Off gassing occurs when chemicals (volatile organic compounds or VOCs) are released into the air from products. Depending on the chemicals used during manufacturing – or simply the chemicals that are part of the materials – these vapors can be dangerous for you and your family’s health.

Common goods that have harmful off gassing include: carpeting, furniture, plastics, faux woods, and paint. Think of that sought-after “new car” smell. That’s the smell of everything in a vehicle off gassing!

Since the unhealthy effects of off gassing and offensive odors are entirely dependent on the type of chemicals used, as well as the time it takes for the off gassing to occur, it’s often hard to determine what’s dangerous and what isn’t. However, there can be both long- and short-term health effects, including headaches, respiratory issues, eye irritation, nosebleeds, and more. 

In short, off gassing isn’t to be taken lightly.

How to choose a vapor barrier that has minimal off gassing


Since nearly every brand new synthetic material will have some sort of off gassing, how can you prevent it? After all, it can take years for chemicals to completely off gas from a substance.

Here are a few tips for better, quicker, and less overall off gassing:

  • Choose products that are certified low or no VOCs.
  • Choose products from a manufacturer that has invested in in-house and private lab testing.
  • Open or unwrap new products in ventilated spaces or outdoors.
  • Do your own research on the product and see if the chemical or urine type smells have been mentioned about it.
  • Over processed (over recycled) polys tend to off gas more.
  • String reinforced two color sided vapor barriers have been labeled as a high candidate to smell long after installation.
  • Cheaper reinforced vapor barriers are suspect for long term off gassing.

In short, vapor barrier manufacturers are not required to test for off gassing, aging, curing, etc. Therefore, the most important thing you can do is look to see what class your vapor barrier is rated. Only Class (A) vapor barriers have been tested well beyond the minimum requirements. However, that’s not to say that some Class C vapor barriers are not of good quality.


Do vapor barriers off gas?


So back to the question at hand: do our vapor barriers off gas?

No, our Viper Liner does not.

Our class (A) viper liner is a premium virgin woven poly. It sets the standard in a number of categories and is one of only a handful of vapor barriers in the world that passes radon and methane testing. It is guaranteed not to off gas and comes with a 25 year manufacturer’s warranty.

Yes, our other vapor barriers off gas, but the off gassing vapor is minimal and mostly just when you unroll it.

Our Class (C) vapor barriers are made of thick, high quality polyethylene. This type of plastic, like many others, does have a “smell” when it’s first rolled out. However, they are produced in a way that won’t off gas dangerous chemicals and any odor is gone within hours.

Also, all of our vapor barriers are manufactured in the USA!


Rest easy knowing you can safely install our vapor barriers in your crawl space without worrying about the health of your family.

And for quality wholesale crawl space products, The Crawlspace Supply Company is here to help!

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