There are as many interpretations of encapsulating a crawlspace as there are Carter’s
Liver Pills. Typically, crawlspace encapsulation refers to sealing a crawlspace and
controlling the air with a dehumidifier.
Historically, homes with crawlspaces used foundation vents to let the crawlspace
“breathe” in the summer, allowing outside air in, while being closed in the winter to help
prevent freezing pipes. While this sounds like routine maintenance, in reality it can
introduce warm, humid air into a cooler crawlspace, raising moisture levels instead of
lowering them.
Wood is hygroscopic, meaning it absorbs moisture from the air. As the moisture
increases, so does the wood moisture content (WMC). Once WMC reaches around
20% or higher, conditions become favorable for wood-destroying fungi, which can begin
breaking down structural members over time. Excess moisture in crawlspaces can
cause damage comparable to termite activity and can also create the conditions
termites thrive in.
National Exterminating brings over 50 years of field experience in both termite control
and crawlspace moisture management. Over that time, we’ve developed a hybrid
approach to crawlspace encapsulation that focuses on reducing moisture while still
maintaining the ability to inspect, treat, and service the space. These systems are
inspectable, treatable, and warrantable, and are designed to balance performance with
long-term practicality.
In recent years, building codes have moved toward unvented crawlspaces, also referred
to as encapsulated systems. While these standards are intended to improve energy
efficiency and moisture control, they can present challenges in real-world applications.
For example, dehumidifier sizing recommendations may not always match manufacturer
specifications for optimal performance in actual field conditions.
Another point of discussion in the industry is the placement of termite inspection strips.
Current building guidance often places this strip at the top of the foundation wall, but
many in the pest management industry prefer inspection points closer to the soil line for
earlier detection and response.
When evaluating full encapsulation systems, homeowners should consider a few
important factors:
- Sealed environments can create conditions that may be favorable for termites
and wood-destroying fungi if not properly managed. - Moisture trapped against foundation walls can contribute to long-term masonry
deterioration, including spalling in some cases. - Spray foam and similar materials can limit visibility and access during future
inspections or treatments. - Some encapsulation materials may need to be modified or removed before a
complete termite treatment can be performed.
The goal of any crawlspace system should be a balance of controlling moisture while
keeping the structure inspectable, treatable, and maintainable over time.
At the end of the day, the most expensive system isn’t always the best system, it’s the
one that still works with how homes actually behave in the real world.
