Seal your crawl space to keep moisture, pests, and cold air out of your home

In Connecticut, sealing the crawl space (unvented) is generally preferred for better moisture control and energy efficiency. Vented crawl spaces allow humid outside air in during summer and cold air in during winter — both of which work against you.

Start with proper drainage around the foundation. Install a vapor barrier on the crawl space floor. Consider sealing off outside ventilation to prevent moist air from entering. Moisture must be controlled before insulation goes in.

Rigid foam board and closed-cell spray foam are generally recommended for their moisture resistance and thermal performance. Both work well on crawl space walls and resist the damp conditions common in below-grade spaces.

Insulating the perimeter walls is preferred for sealed (unvented) crawl spaces. This brings the crawl space inside your home's thermal envelope, keeping it warmer and drier than ceiling-only insulation would.

A vapor barrier is a material placed on the crawl space floor to prevent moisture from the soil from rising into the space. It is highly recommended alongside proper insulation — especially in Connecticut where ground moisture is common.

Yes. Properly sealing and insulating a crawl space removes habitats and closes entry points that rodents, insects, and other pests rely on. A sealed crawl space is far less inviting to wildlife than an open, vented one.

Some families tackle this as a DIY project, but professional installation gives the best results — especially when it comes to moisture control and air sealing, which are easy to get wrong. A proper assessment also determines whether your project qualifies for the Energize CT rebate, which can cover 75–100% of the cost.

For vented crawl spaces, proper ventilation and moisture-resistant materials are key. We generally recommend a less moisture-absorbent insulation such as rigid foam or properly shielded fiberglass, rather than materials that can trap dampness against the structure.