Thread: Commercial ventilation

I recently inspected a small office building and noted that the HVA/C blowers were not operating continuously. My understanding is that continuous blower operation is required to provide fresh air from the exterior when the building is occupied. None of the windows open.

From the International Mechanical Code:

401.3 When required. Ventilation shall be provided during the periods that the room or space is occupied.

403.3 Ventilation rate. Ventilation systems shall be designed to have the capacity to supply the minimum outdoor airflow rate determined in accordance with Table 403.3 based on the occupant load or other parameter as stated therein. The occupant load utilized for design of the ventilation system shall not be less than the number determined from the estimated maximum occupant load rate indicated in Table 403.3. Ventilation rates for occupancies not represented in Table 403.3 shall be determined by an approved engineering analysis. The ventilation system shall be designed to supply the required rate of ventilation air continuously during the period the building is occupied, except as otherwise stated in other provisions of the code.

My questions are:

1) Do I have this right? Is continuous mechanical ventilation required?
2) Is there some exception such as a small office occupancy?
3) Am I using the correct code section?

Thank you so much for your time and effort


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What is this? Question too hard? 10 lookey-loos and no responses.

Sheesh.

Originally Posted by Gunnar Alquist

My understanding is that continuous blower operation is required

I don't see where it specifies "mechanical ventilation", just "ventilation".

Also, that would not be a requirement for the "conditioning system", i.e., the a/c, to run continuously. To do so would created all kinds of problems.

From the 2006 IMC.

- VENTILATION.The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, any space.

My questions are:

1) Do I have this right? Is continuous mechanical ventilation required?
2) Is there some exception such as a small office occupancy?
3) Am I using the correct code section?

1) No and no.

2) Not needed.

3) Mis-reading the code section.

JP,

I did not really mean the A/C, just the blower to provide ventilation. This building is two story and has no operable windows. Since no natural ventilation can be provided (unless you can allow for air leakage at windows & doors), some type of mechanical ventilation would be necessary. And, since the only system available are the heat pumps, then they would, most likely, be the ventilation system.

No?

Originally Posted by Gunnar Alquist

No?

Yes - No. That is the short answer.

The better answer is that the buildings are required to have make up air openings, and other ventilation requirements, and all of those added together make up the ventilation system.

Not having been there, I can't tell you any more about that building, other than ... no, mechanical ventilation is not required to be operating at all times in all buildings. In some, yes, they are designed for to have continuous mechanical ventilation. Other buildings are not.