Here are the basic features of an encapsulated crawl space:
- 100% coverage of the ground with a vapor barrier
- Seams and junctions of vapor barrier sealed
- Sealed crawl space vents
- Insulated foundation walls and band joist (usually)
- Conditioning of air with one of three methods: (i) dehumidifier, (ii) small amount of supply air from HVAC system, or (iii) small exhaust fan
The benefits of this treatment are significant. As shown in the first article of this series, the relative humidity will stay below 60%, even when the outdoor humidity is much higher. With dehumidification, it’s not difficult to reduce the humidity to less than 50%.
Some other benefits are:
- Better air quality in the crawl space, which means better air quality in the living space
- Greater energy efficiency. The Advanced Energy studies have found nearly 20% reduction in energy use in homes with a conditioned crawl space.
- Fewer critter problems
- Greater durability of floor, HVAC equipment, and other components in the crawl space
- Greater comfort in the home because of reduced humidity and crawl space temperatures close to living space temperatures
There are also, of course, some caveats that come with this method of treating crawl spaces. For one, a crawl space with atmospheric combustion appliances should not be encapsulated. Second, all bulk water problems need to be fixed before encapsulating. And third, building officials and pest control companies have to be on board to prevent problems down the road.