Crawl Space Vapor Barrier

Why install an EcoTreck Crawl space system?

An unfinished crawl space can present moisture issues, harbor mold and decrease a home's energy efficiency. A finished crawl space can result in a greener, healthier home.

Unfortunately, an unfinished crawl space can also be quietly undermining the integrity of the home and life within it. The crawl space like many unfinished basements tends to be quite humid. The excessive moisture in a crawl space poses a number of threats to the home. It provides an environment for mold to thrive, mold that can eventually make its way up into the rest of the home. It can reduce the indoor air quality of the living areas above; the moisture can also attract wood-boring insects that destroy the wood sub-structure. The presence of insects may also draw rodents and other pests into the crawl space. Unfinished crawlspaces may cause moisture-related problems to the structure of the home and increase utility costs. Solving the crawl space moisture issue is the first priority in a crawl space finishing project.

What is my crawlspace for?

Crawls spaces may appear to serve little purpose, but in truth they have a few important functions. To start, a crawl space may have been used in place of a basement to save cost. The crawl space elevates the home off the ground which can be a necessity in particularly damp or termite-prone locations. The crawl space can also house the plumbing and ductwork of a home and grants access to repair or service those systems.


Many crawl spaces have built-in ventilation to allow airflow-a code-enforced design originally intended to mitigate moisture. The latest studies on crawl space ventilation indicate that, in some climates, ventilation is actually contributing to moisture and humidity in the crawl space. Furthermore, ventilation allows winter cold to have free passage under the home, which can result in higher heating bills. Fortunately, there are some simple ways to "finish" the crawl space to reduce the moisture issues and increase energy efficiency.

Moisture Mitigation: Vapor Barriers and Encapsulation

The elimination of moisture and reduction of humidity in the crawl space is crucial to a healthy home. This step will help control mold growth, wood rot and insect infestation, which can also alleviate any rodent issues. Reducing moisture can put an end to any mustiness or unsavory smells emanating from the area. It will also prevent the hardwood floors above from warping.


Moisture and humidity in the crawl space is partially the result of water evaporating from the soil. To combat moisture in the crawl space, a vapor barrier or encapsulation system can be installed. Encapsulating the whole crawl space is the best bet. An encapsulation system usually sees a moisture/vapor barrier or "liner" installed up the walls of the crawl space and over the exposed earth floor. Overlapping the liners of the wall and the floor with a 10 to 90 mil puncture resistant liner, taping all the seams and fixing the barrier to the foundation walls with a termination bar is the typical encapsulation system used By EcoTreck.

Just installing a vapor barrier most likely won't be enough, however. Professionals may recommend installing a drainage system along the perimeter of the crawl space walls and a sump pump to keep the ground beneath the liner dry. Leveling the dirt floor will be an option or a necessity, depending on whether or not the homeowner wants to pour a concrete floor, a more expensive crawl space finishing solution. A level crawl space is more conducive to storage usage and will decrease the chances of tearing a hole through the liner.

Some crawls spaces need a lot of work. Fiberglass insulation may need to be removed and replaced. Broken or leaking pipes, drier vents and other elements found in the crawl space may also be a source of moisture and humidity.

Crawl Space Ventilation and Energy Efficiency:

For some time, vents were code-enforced features on crawl spaces around the country. Recent findings have suggested that year-round venting of the crawl space is not beneficial for homes in every climate. In some cases, it can actually have a negative effect on both humidity levels in the crawl space and energy costs in the home.

Current thinking holds that the difference in air temperature outside the home to the temperature in the crawl space during the hot summer months causes moisture condensation inside the crawl space. Condensation forms on pipes, joists and just about every surface in the crawl space area, leading to mold growth and wood rot, which invites termites.

In the cold winter months, the vented crawl space permits cold outside air into the home. This cools down the pipes and heating elements in the crawl space (furnaces, ductwork, etc.), which can increase utility costs. It also can turn the floor above into an uncomfortably frigid surface to walk on. This process starts by blocking up the vents. You want to treat the crawl space just like any other room in the home. In some cases Styrofoam blocks and open cell spray foam may be used on the interior of the crawl space-the vents stay in place but are rendered useless by the Styrofoam.

Ongoing studies like the one conducted by Advance Energy and the Department of Energy ( www.crawlspaces.org ) have proven the theory that an unvented, closed crawlspace is the most energy efficient design in the crawlspace of a home. To get the most "bang for the buck," insulate the crawl space walls, not the ceiling. If given the choice between the walls and ceiling, the Department of Energy says to insulate the walls, not the ceiling. Heat transfer always moves from hot to cold or from inside the home to outside and down into the crawl space. When insulating the crawl space, it is best to use an aluminum faced material to reflect heat back into the home.

It is important for a homeowner to check local code before blocking off crawl space vents. In some areas vents are required. Flood states, for example, require flood vents in this area of the home to prevent water pressure from destroying the foundation in the event of a flood. Crawl spaces that house a furnace or hot water heater may need make-up air for combustion purposes.

"Conditioning" the Crawl Space:

To treat the crawl space like any other room in the home means "conditioning" it. In a crawl space that contains the ductwork for the home's heating system, conditioning the space is as simple as installing a register. This simple step will help keep the crawl space at the same temperature and humidity level as the rest of the rooms in the home. "The air becomes conditioned by using the existing HVAC system.

Of course, not all homes will have the option of installing a register in the crawl space area. For many homes, it may be necessary to use a dehumidifier in the crawl space area. Dehumidifiers vary widely-from small portable units on casters to crawl space-specific models that can be plumbed in to the home's drainage system. EcoTreck has a few options to choose from.

Finishing the crawl space area can be a large undertaking. But leaving the crawl space area a humid, musty and energy-inefficient hole in the ground can result in an unhealthy home, substructure damage and high utility costs. Proper encapsulation, ventilation blocking and crawl space conditioning will help green the home and keep the temperature, humidity and energy bills at a comfortable level year-round.

© Copyright 2018 EcoTreck Environmental Solutions

EcoTreck Environmental Reviews