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 Lakes Area Flood & Fire.                                                                   

         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. A video of interest: Crawl Space Vapor Barrier Benefits (youtube.com) 

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. A video of interest: Crawl Space Vapor Barrier Tour (youtube.com)   

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. Lakes Area Flood & Fire has a few options to choose from. A video of facts: Crawl Space Vapor Barrier Facts (youtube.com) 

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.