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How crazy is my plan to circulate air in 350 sq. ft. of space with closed doors and no windows?

TB93 | Posted in GBA Pro Help on

I’m working on a 650 sq ft office suite located in Los Angeles. The space is split roughly in half: two therapists offices (windowed) take up one half. A waiting room, hallway, bathroom and kitchenette (none windowed) take up the other half.

The therapists offices currently have in wall ACs that are too loud for therapy. We’re looking at Ductless ACs as an alternative but the budget only allows for a Dual Zone system. The indoor units would have to go in the therapists office, there is really no alternative here.

Where it gets tricky: because of the nature of therapy, the doors to the offices (where the indoor units would be located) will be closed 99% of the time.

So the question becomes: how to cool / heat / move air through the other half of the office?

My thought was to install ceiling vents in the offices and run 6″ ducts to an inline ductfan that blows into the closed off, non-windowed side of the office. From what I’ve read, the volume of air in the closed off half should circulate 2-4 times an hour. Let’s say the closed off side is 350 sq ft x 8 high, that equals 2800 cubic ft. Multiply that by 4 times an hour = 11,200 ft per hour – or 186 cubic feet per minute.

If I run vents to an inline duct fan that can move 186 cubic feet of air per minute, could I realistically circulate enough air through the closed off half of the office? Do I also need to run returns?

I should also note the office is under renovation. The walls and ceiling aren’t up yet, it is no problem to run duct work at this stage. I’m also assuming the ductless AC would have to be in the 12-14BTU range since they’d be servicing the entire office.


  1. User avatar GBA Editor
    Martin Holladay | | #1

    First of all, can you tell us your name?

    While it's true that a noisy air conditioner isn't desirable in a therapist's office, a noisy air conditioner is definitely desirable in a therapist's waiting room. That's why many therapist's waiting rooms have a "white noise" machine -- to cover up the sound of confidential therapy sessions which shouldn't be overheard by waiting clients.

    Is there any way to install a through-the-wall air conditioner (a cheap noisy one) in the waiting room?

  2. TB93 | | #2

    Hey sorry, my name is Jesse.

    I think I could put an in-wall unit in the lobby - however - there is a security door blocking airflow from the lobby to the hallway / kitchenette / bathroom.

  3. User avatar GBA Editor
    Martin Holladay | | #3

    For an answer to your question about using a fan to equalize temperatures in adjacent rooms, see this article: "Using a Bath Fan to Equalize Room Temperatures."

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