Mechanical Ventilation in Multi-Family Apartment Buildings through Exhaust

[nuuvox000]

It's pretty common in my city that all of the apartment buildings are ventilated through the exhaust fans in the bathrooms, i.e., the bathrooms exhaust air continuously and fresh air is expected to come into the unit from the exterior wall and through cracks in the exterior windows. This is what we have been doing as well for a few years but it makes me uneasy every time we do this.

Can 40 to 50 CFM really come through cracks in the exterior wall? Part of me thinks that the fans are just running ragged due to the negative pressure. Please let me know your thoughts and if you've had experience with this.

 

[EnergyProfessional]

The fan flow should be measured to verify.

for achieving the desired EA flow I would be more concerned with the cheap plastic flex duct that is being used. But the flow test will tell.

Yes, with the crappy building construction there will be enough infiltration. the problem is, the occupants will get "fresh" air that came through the wall where there is all the dirt, microbiological growth (especially if you have AC). So it meets code, but isn't great.

 

[nuuvox000]

Thanks for your thoughts.
I will definitely measure the airflow of the next building we finish up.
We typically use aluminum ductwork for the exhaust fans so that should help.
I wish it didn't meet code because it's pretty much impossible for me to push the extra equipment and space required to use a DOAS for all of the units when nobody else is bidding projects that way.