Excess moisture, introduced by way of unsealed, vented crawl spaces, contributes to wood rot, mold growth and increased pest activity, including infestation and colonization. Moisture in crawl spaces often migrates to the upper levels of the home through a “stack effect”. In essence, whatever air is below the house is also inside the house. As warm air rises and escapes through the upper levels of the home, new air finds its way into the home to replace what’s been lost. Intake air comes in at the lower levels — through unsealed crawl spaces. This may lead to costly problems such as cupping of hardwood floors, mold growth, increased air conditioner loads, and swelling of millwork/cabinetry. Air infiltration from the crawl space often carries odors and may contribute to poor indoor air quality and uncomfortably high humidity levels.
Excess moisture in crawl spaces has also been associated with contributing to increased energy consumption. Wintertime ventilation cools the crawl space contributing to heat loss from the home. In the summer, introducing warm outside air under the home contributes to heat gains, increasing cooling loads. Ventilation of a crawl space to control relative humidity only works consistently in an arid climate. In most climates, ventilation can actually add significant quantities of moisture during humid times.
Crawl Space Facts
- According to a study by Advanced Energy, homeowners can expect to reduce their energy bills by 15–18% by sealing off their crawl space. They also determined that homes with vented crawl spaces were 19 times more likely to experience relative humidity levels in excess of 70% than homes with encapsulated crawl spaces.
- As much as 50% of the air in a home’s living space originates from the crawl space.
- Most pests are attracted to moist environments; as a result, moisture control is an important part of any fully integrated pest management system.