The idea having a sealed, or technically “closed”, crawl space in your home is interesting.
First though, what is a crawl space? A crawl space is the area within the foundation walls between the earth and a house’s under-floor framing.
Traditionally, this area is passively ventilated by screened openings in the foundation wall.
However, ventilation has some drawbacks. It lets in moist air, cold air in and insects and rodents can enter. These factors are a concern to home owners due to potential for odors, molds, decay, higher energy costs, higher maintenance costs, etc.
A closed crawl space does not share its air with the outdoors; rather it has a pressure fed
duct that is tied to the homes HVAC system and/or having a dehumidifier. The under-floor areas are not insulated as in a standard crawl space; however, the inside perimeter
foundation walls are insulated with foam board or spray foam. The earth is covered with a polyethylene barrier that extends up onto the inner foundation walls. This helps keep moisture from emanating from the earth and into the crawl space.
During a home Inspection, it is critical to assess the crawl space for moisture problems. A closed crawl space can create additional concerns and problems if all components are not installed properly.
A recent closed crawl space inspection we completed on new Clayton, NC home revealed
enough moisture that the floor sheathing, framing and foundation wall insulation were
covered with condensation. Unfortunately, mold was present as well. The soil under the
poly vapor barrier was very soft and squishy; wet soil, in other words.
A closed crawl space with the introduction of moisture ends up acting as a trap since
there is no external ventilation. The mixing of the home’s HVAC air into the crawl
space, or a dehumidifier, would never be enough to take care of such excessive moisture.
Some of the problems we noted during our Home Inspection included gaps between the
polyethylene vapor barrier and the foundation walls and block piers which allowed
moisture to seep from the ground into the “sealed” area. These gaps, combined with
direct water entry into the crawl space, caused significant problems.
My home inspection client called me to thank me for the thorough job I did and to tell
me that my service was paid for many times over. My client was in the process of
consulting with a third party to help ensure the builder’s corrective measure was the most
prudent course of action.
A closed crawl space has many benefits and can contribute to a healthy home as long as
the whole “system” is functioning properly.
What’s in your crawl space? If you don’t know, let us take a look today.
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