Pressure/flow relationships of crawl space foundation vents were determined and used in evaluating crawl space ventilation of three houses. Vent effective leakage area (ELA) ranged from 8% greater than net free area (NFA) for the smallest NFA vent to an ELA of 50% less than NFA for some larger NFA vents. Vents with low NFA provide more ventilation ‘per gross ventilation area’ than vents with high NFA; two 0.015 m2 NFA vents supplied the same ventilation as one 0.048 m2 NFA vent. Vents installed according to building code requirements using state NFA may be providing up to 50% less ventilation than calculated by ELA. Fan pressurisation tests on three houses indicated that the ELA of the crawl space with existing vents closed and sealed was greater than 1/1500 of the gross floor area in all test cases. When existing vents were opened, ELA increased by 100% to 350%. ELA of the existing vents indicated less ventilation compared to NFA.
KEYWORDS: crawl spaces, ventilation, air flow, vents, pressurisation, measuring, housing, testing.
Citation: Symposium, ASHRAE Trans. 1994, Vol.100, Part 1,
Product Details
- Published:
- 1994
- File Size:
- 1 file , 1.3 MB
- Product Code(s):
- D-17985
