Methodology
 Natural Ventilation Rate

Blower Door

Testing natural air exchange with blower door

Three rooms were tested with a Minneapolis Model 3 Blower Door. The Test Method chosen is known as ACH50. This method measures the airflow necessary to pressurize the building to 50 Pascals. The seasonal amount of natural air exchange is estimated using the divide by 20 rule or by an estimated correlation factor. One test was done with the window sealed with tape and one was done without sealing.

Steps for blower door usage

1. Measure room dimensions to calculate area and volume.
2. Measure ambient temperature inside and out.
3. Turn off all combustion appliances.
4. Verify condition of intentional openings.
5. Decide on configuration of doors to semi-conditioned spaces.
6. Set up Minneapolis blower door.
7. Set gauges to zero.
8. Take measurements.

Correlation Factor

N = C * H * S * L

where:

C = climate factor, a function of annual temperatures and wind
H = height correction factor
S = wind shielding correction factor
L = leakiness correction factor

For the YMCA,

C= 25
H = 0.7
S = 1.0
L = 0.7

So, Correlation Factor, N = 12.25

By installing new windows in the residence rooms at the Berkeley YMCA the ventilation rate will fall below the ASHRAE standards.