Sealing a crawl space keeps outside moisture out, but whatever moisture is already in the air stays trapped. That's why most encapsulated crawl spaces include a dehumidifier, and many add wall insulation for warmer floors and better protection against frozen pipes.
Crawl space dehumidifiers
- Built for the space. Crawl space units run efficiently at cooler temperatures and fit in low clearances.
- Continuous drainage. They drain to a sump pit, a condensate pump or outside, so there's no bucket to empty.
- Humidity target. Most are set to keep relative humidity below about 60%. The EPA recommends indoor humidity below 60%, ideally 30% to 50%.
- Cost. Installed crawl space dehumidifiers typically run about $800 to $2,000, according to This Old House.
Questions to ask about a dehumidifier
- What brand, model and capacity (pints per day)?
- Where will it drain?
- Does it need a dedicated electrical outlet?
- How often does the filter need changing, and what's the warranty?
Want a dehumidifier or insulation installed? Call to get a quote.
Call: (317) 426-0557Crawl space insulation
Where insulation goes depends on whether your crawl space is vented or sealed:
- Vented crawl space: insulation typically sits between the floor joists. In damp crawl spaces, this fiberglass often absorbs moisture, sags and falls down.
- Sealed or encapsulated crawl space: insulation commonly goes on the foundation walls instead, so the crawl space stays closer to indoor temperatures. That can mean warmer floors and lower risk of frozen pipes during Indiana winters.
Typical insulation costs
| Type | Typical cost |
|---|---|
| Fiberglass batts | $0.60 – $1.10 / sq ft |
| Spray foam | $1.00 – $3.50 / sq ft |
| Rigid foam board | $2.50 – $3.00 / sq ft |
Source: This Old House crawl space encapsulation cost guide.
Signs you need better humidity control
- Musty odors that come back even after cleanup.
- Condensation on ducts and pipes in summer.
- Sagging, wet insulation.
- Cold floors in winter.
Frequently asked questions
What humidity should a crawl space be?
A common target is keeping relative humidity below about 60%, since mold and dust mites thrive above that. The EPA recommends indoor humidity below 60%, ideally between 30% and 50%.
Can I use a regular household dehumidifier in my crawl space?
Household units aren't built for cool, low-clearance crawl spaces and usually need their buckets emptied. Crawl space dehumidifiers are designed to run in cooler temperatures and drain continuously.
Should I insulate the floor or the walls of my crawl space?
In a vented crawl space, insulation usually goes between the floor joists. In a sealed or encapsulated crawl space, insulation commonly goes on the foundation walls instead, bringing the crawl space inside the home's thermal envelope. Your contractor should explain which fits your home.