Figure 4 Wind sure to drop inside the building. Exhaust fans that suck air out of the building also lower the pressure in the building and suck air in from outside. Figure 6. Measuring Pressure Oilheat technicians measure air pressure using inches of water column. One inch of water column is the pressure difference required 32 National Oilheat Research Alliance Figure 5 Stack Effect to draw water one inch up a straw. Home performance contractors use Pascals (Metric Standard). One Pascal equals the weight of one Post-it Note and 248 Pascals = 1” WC (American Standard) so 2.5 Pascals = .01” WC. The Building Envelope Energy efficient homes are wrapped in a continuous “building envelope” that con- Combustion Air Figure 6 and Venting Exhaust Fans
NORA Advanced Efficiency
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