Overview: Definition of Crawl Space

Before seeking crawl space vapor barrier installation in Knoxville, TN it’s important to understand some basics. The crawl space is simply the crawlable space under your home (unoccupied and/or unfinished narrow space between the floor and the ground). Most plumbing and wiring are found in the crawl space. Some people also use the space for storage and installing HVAC units.

The crawl space is potentially subject to high levels of moisture. Though it’s generally considered to be a small issue, flooded crawlspaces and mold are potential hazards that can result from excess moisture in the crawl space where any wood flooring or material is exposed to ground level for an extended period of time.

 The crawl space also has poor air circulation which makes it a perfect place for mold to start and grow.

Vapor barriers in the ground are not uncommon yet they can be quite expensive. The most common reason for installing a crawl space vapor barrier is to keep any moisture from getting into the building and to prevent mold from growing underneath.

What is the Importance of Crawl Space?

Crawl spaces are important for creating a buffer between the home and the space under the home. It is also cost-effective to build a home over a crawl space when the location is hilly. Alternatives such as moving dirt are costly. Crawl spaces built over flat ground prevents flooding in case of heavy rain.



While crawl space has notable benefits, it also comes with a fair share of problems. Unfortunately, many homeowners overlook crawl space problems and do not invest in a solution.  They disregard crawl spaces as an area that generates humidity when it is in fact not the case. The humidity concern in crawl spaces is not a myth.

Crawl Space Related Problems

Homes built over crawl spaces usually suck water vapor from the ground. This vapor ends up inside the home resulting in dampness and mold problems. Besides damaging a home, moisture is linked to many respiratory infections, among other health problems. The solution to crawl space vapor problems is a crawl space vapor barrier.

Crawl Space Vapor Barrier

A crawl space vapor barrier is simply a plastic liner covering the dirt on the ground of a crawl space. The barrier works by blocking vapor from the soil from being getting into the crawl space. Most houses have floors made of porous materials (wood, fiberglass, and concrete) that let in moisture.

What's more, HVAC units located in crawl spaces pull air from the crawl space. The quality of such air is important for obvious reasons. To avoid mold, respiratory health problems, allergies, and insect infestation (attracted by decaying moist wood/matter), the importance of a crawl space vapor barrier can't be overlooked.

But you can't just consider any crawl space vapor barrier installation in Knoxville. There are many vapor barriers on sale today, most of which aren't great for homes. When searching for the best crawl space vapor barrier, you should focus on the thickness and permeability of the plastic barrier you are buying.

Too thin, and it won't work as you want. Too permeable, and the vapor barrier will be of no use. Most crawl space barriers on sale today are easily penetrated by moisture (causing mold). It is therefore important for homeowners to avoid such products.

Difference between a cheap 6 mil vapor barrier vs. high-quality vapor barriers designed for crawl spaces

Vapor barriers are usually categorized by thickness and permeability. The cheapest barriers are thin. They feature plastic (polyethylene) that is 6 mil thick (0.006 inches). 6-mill vapor barrier is the minimum thickness for crawl space vapor barrier available today. While it may be cheap, it doesn’t act as a great barrier. You should consider anything between 10 mil and 20 mil thickness for crawl space application.

High-quality vapor barriers also have a low permeability rating, which means they won't let vapor or water pass through them easily. Ideally, you should buy crawl space vapor barrier for your Knoxville home that has a 0.1 permeability rating or lower.

Polyethylene vapor barrier that is thicker than 10 mil and has a permeability rating of 0.1 and below will work for a home. However, high-quality vapor barriers are thicker than normal and have an impressively low permeability rating.

How high-quality vapor barriers helps reduce moisture buildup in the crawl space and improve indoor air quality

While less permeability and more thickness are generally good, the ultimate choice of crawl space vapor barrier should be dictated by the material/soil covering the crawlspace and how a crawl space is being used.

For instance, a crawl space that will be entered frequently should have the thickest vapor barrier possible to withstand constant traffic. Remember, a punctured barrier will let in moisture. Ideally, the best vapor barrier is one that will keep moisture off regardless of application. The vapor barriers are puncture resistant and treated to prevent the growth of harmful fungi, mold, and bacteria.

High-quality vapor barriers eliminate moisture buildup in crawl spaces by blocking moisture and vapor in the soil from getting into the crawls space and finding its way into the home via porous flooring.

Most importantly, the added thickness and less permeability of high-quality vapor barriers eliminate moisture buildup for decades. The best vapor barriers in the market today will keep crawl spaces dry and free of moisture for 20 or more years guaranteeing better air quality and low respiratory disease risks. However, the barriers must be installed properly.