Blower Door Testing

[CuriouslyGeorge]

What can you tell me about the practical meaning behind the numerical results from a blower door test??? For example, I have 1000 ft^2 area I wish to pressurize to a desired value of "x" iwg. The blower door test says I need 500 cfm to achieve "x" iwg. (I assume, a low cfm result means the room is well sealed.) But...the supply air (SA) flow to the area is normally 1500 cfm.

Does this mean, to achieve "x" iwg, I need to supply a total of 1500 cfm SA + 500 cfm more? Is that the practical meaning of the results?

Thanks,
- CuriouslyGeorge

 

[imok2]

To perform a thorough energy efficiency analysis of a room, energy advisors use specially designed "blower door" test equipment to measure your room's rate of air leakage.
The blower door is a variable-speed fan mounted on an adjustable panel that can fit into any door opening. When the energy technition turns on the fan, the pressure inside your room is gradually reduced to allow outside air to flow into the room through unsealed opening or cracks in the room structure. Pressure gauges connected to the fan measure the rate of airflow required to keep the room at a constant pressure so that the technition can calculate your room's resistance to air infiltration.
While the fan is still running, the technition will walk though the room to see, using a smoke pencil, the exact points where the room is leaking air and where it needs to be sealed. So you need to shut the air flow to the room and according to your specs remove 500 cfm and ck for leaks

 

[KenRad]

I believe that the test results indicate that you need to supply 500 CFM of EXCESS air to the room to maintain the desired pressurization. If the 1500 CFM you are currently supplying all comes from the room itself (that is, no outside air is introduced), then your room pressure is probably neutral with respect to its surroundings. To cause the room pressure to rise, you need to bring in air from outside the room into your AHU return plenum. This can be outdoor air, conditioned air from another part of the building, or some combination of both. Ensure that you are satisfying mechanical code requirements for outdoor air according to room occupancy.

Keep in mind also that if you have any exhaust fans in the room, the amount of excess air will have to be increased to makeup for the air that you are removing by exhaust.

---KenRad