Moisture Control Calculator

Size crawl space vapor barriers, ventilation per IRC R408.1, dehumidifier capacity, and estimate encapsulation or vented system costs.

Inputs

Crawl space area (ft²)

Crawl space height (ft)

System type (0=Vented, 1=Encapsulated)

Barrier thickness (mil)

Current humidity (%)

Target humidity (%)

Tab to move between fields

Results

Vapor barrier needed (ft²)

1,777

Total project cost ($)

$4,357.15

≈ 4 smartphones

Barrier material cost ($)$284.36

Foundation vents needed0

Dehumidifier capacity (pints/day)24

Dehumidifier cost ($)$992.00

Sump pump recommended (1=Yes)0

Installation labor ($)$3,000.00

Total material cost ($)$1,357.15

Cost per ft² ($)$3.63

Crawl Volume Cu (ft)3,600

How to Use This Calculator

Enter crawl space area in square feet and measured relative humidity percentage.
Input the number of foundation vents and their total open area in square inches.
Set the vapor barrier coverage percentage over the crawl space soil.
Review the Moisture Risk Level and the Recommended Dehumidifier Capacity in pints per day.
Use the Ventilation Rate output to determine if additional vents or mechanical ventilation are needed.

How the result changes with Crawl space area (ft²)

Crawl space area (ft²)	Vapor barrier needed (ft²)	Total project cost ($)
1,045	1,576	$3,904.34
3,533	4,671	$11,160.16
6,518	8,235	$19,835.02
9,005	11,158	$27,052.98

What each input means

Crawl space area (ft²): Total crawl space floor area in square feet.
Crawl space height (ft): Average crawl space height from ground to floor joists.
System type (0=Vented, 1=Encapsulated): 0 = Traditional vented crawl space. 1 = Full encapsulation (sealed, conditioned).
Barrier thickness (mil): Vapor barrier thickness. 6 mil is minimum code; 12–20 mil recommended for encapsulation.
Current humidity (%): Current relative humidity in the crawl space.
Target humidity (%): Desired relative humidity. Below 60% prevents wood rot and termites.

What each result means

Vapor barrier needed (ft²): Total barrier material including 10% overlap allowance.
Barrier material cost ($): Cost of vapor barrier material.
Foundation vents needed: Number of foundation vents (vented system only, per IRC R408.1).
Dehumidifier capacity (pints/day): Required dehumidifier capacity for encapsulated systems.
Dehumidifier cost ($): Cost of commercial-grade crawl space dehumidifier.
Sump pump recommended (1=Yes): Recommended if current humidity exceeds 80%.
Installation labor ($): Professional installation labor cost.
Total material cost ($): All materials including barrier, dehumidifier, vents, and supplies.
Total project cost ($): Combined material and labor cost.
Cost per ft² ($): Total project cost per square foot of crawl space.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Crawl space area (ft²) = 1200, Crawl space height (ft) = 3, System type (0=Vented, 1=Encapsulated) = 1, Barrier thickness (mil) = 12 = 6 input(s) provided
Calculate Vapor barrier needed
Vapor barrier needed = barrierSqFt * 1.1
1777 = 1777
Calculate Total project cost
Total project cost = totalMaterialCost + laborCost
4357.15 = $4,357.15
Calculate Barrier material cost
Barrier material cost = barrierWithOverlap * barrierCostPerSqFt
284.36 = $284.36
Calculate Foundation vents needed
0 = 0

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