What size dehumidifier do I need for a crawl space?

At least 70 pints per day per 1,000 sq ft of crawl space floor, the IRC figure for the dehumidification option. For 1,200 sq ft that is 84 pints a day.

Can I use a basement dehumidifier in a crawl space?

Crawl spaces are cooler and tighter than basements. Check the unit is rated for the temperatures there and can drain without a bucket.

Is this in every building code?

The 70-pint option appears in the 2018 IRC text we read. Your jurisdiction adopts an edition and may amend it.

Do I still need a vapor barrier?

Yes. An unvented crawl space needs a continuous Class I vapor retarder as well as the conditioning method.

HyreFoundation tools

Crawl space dehumidifier size calculator

The IRC’s dehumidification option sets 70 pints a day for every 1,000 sq ft of crawl space floor.

A crawl space dehumidifier size calculator uses the figure in the building code: in the IRC editions that include it, the dehumidification option for an unvented crawl space is sized to remove 70 pints of moisture per day for every 1,000 square feet of crawl space floor.

Enter your floor area and the tool gives the minimum pints per day. A 1,500 sq ft crawl space needs at least 105.

Crawl space dehumidifier size calculator

The IRC’s dehumidification option sets 70 pints a day for every 1,000 sq ft of crawl space floor.

— Minimum capacity

— How it was worked out

— Before you buy

What this assumed —

Code minimum for the dehumidifier option. Your adopted edition governs.

When this number applies

Only to a sealed crawl space. R408.3 lets an unvented crawl space use one of several conditioning methods. Dehumidification is one; supply air from the house and continuous exhaust at 1 cfm per 50 sq ft are others. A vented crawl space is a different design.

It is a floor, not a target. A crawl space with a water leak, open vents or torn liner can need more. Fix the water first.

Aim for the right humidity. EPA advises keeping indoor humidity below 60%, ideally 30 to 50%. A hygrometer in the crawl space tells you if the unit keeps up; see ideal basement humidity.

Questions this calculator answers

What size dehumidifier do I need for a crawl space?: At least 70 pints per day per 1,000 sq ft of crawl space floor, the IRC figure for the dehumidification option. For 1,200 sq ft that is 84 pints a day.
Can I use a basement dehumidifier in a crawl space?: Crawl spaces are cooler and tighter than basements. Check the unit is rated for the temperatures there and can drain without a bucket.
Is this in every building code?: The 70-pint option appears in the 2018 IRC text we read. Your jurisdiction adopts an edition and may amend it.
Do I still need a vapor barrier?: Yes. An unvented crawl space needs a continuous Class I vapor retarder as well as the conditioning method.

Sources and methodology

Figures dated 26 October 2026. Last reviewed August 16, 2026.

International Residential Code R408.3, unvented crawl space: vapor retarder laps, wall extension and the 70 pints per 1,000 sq ft dehumidification option (2018 edition text) (International Code Council, read via UpCodes, retrieved 2026-10-26. Model code. Your jurisdiction adopts an edition and may amend it.)
A Brief Guide to Mold, Moisture and Your Home: keep indoor humidity below 60%, ideally 30 to 50% (U.S. Environmental Protection Agency, retrieved 2026-10-26)

Vapor barrier calculator The liner the code also requires.
Ideal basement humidity The target to hold.
Crawl moisture check Is it working?
Crawl space repair Vented or sealed.

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Crawl space dehumidifier size calculator

When this number applies

Questions this calculator answers

Sources and methodology

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