Steps to Determine Crawl Space Ventilation Needs
- Measure square footage to be ventilated.
- If ground cover vapor retarder is not used, divide the square footage by 150 to determine needed vent space. Then consult the obstructions chart and multiply venting by the number given for the type of material used.
- If ground cover vapor retarder is used, vented area may be reduced to 1/1500 of the floor area.
- Determine location of needed vents. (See Figure 3.)