Advice about ventilation to air shafts in historic apartment buildings?

February 15, 2013 10:31 AM

Have you lived in an apartment in which some rooms are vented only to an air/ventilation shaft? What was your experience?

I was in an apartment that will be for rent soon - it is gorgeous, but the kitchen and bathroom windows both vent to an air/ventilation shaft that is not vented outside - just to a closed skylight (very old stone building in Ontario, Canada, late 1800s). There are no fans in either room and the windows are high (opened with a chain).

The building, which is an old mansion converted in apartments, is three stories, and this apartment is on the second floor. The kitchen is about 12' X 9' and the bathroom is usual bathroom size. There are three other big rooms to the apartment, all of which have external windows. The nearest external window to the bathroom and kitchen is about 21' away (not a straight line).

I am a bit of a fresh air junkie, and would generally rather be cold and feeling fresh than warm and cozy. In my current place, I crack open the bathroom window when I shower, even in the heart of winter. All of this makes me worry that the bathroom and kitchen venting situation in this place would bother me. If you have lived in this type of arrangement, what was your experience? Thanks!

posted by analog to Home & Garden (7 answers total)

It all depends on whether the apartment has a positive or negative pressure. If the extraction is quite powerful (creating a negative pressure in the apt) you will get airflow through the apt to the to the shafts. You say there isn't any mechanical ventilation in the apt. Is that also true of the shafts? It seems like one would want to put mechanical extraction there to clear the smells of the bath and kitchen. If there is mechanical ventilation in the shafts then you should be OK. The low pressure created will draw in fresh air from any open windows.

We have a similar situation but have tremendous vacuum from the ventilation ducts in the kitchen and bathroom (I suspect this is b/c other tenants have blanked their vents off). Our situation is great except we are on a busy road and don't want the windows open most of the time. But the windows are our only source of fresh air as the cheap-ass builder didn't install fresh air supply ducts.

Good luck!
posted by pandabearjohnson at 10:49 AM on February 15, 2013

Response by poster: Thanks for the response, pandabearjohnson - to answer your question, there is no mechanical ventilation in air shaft, either. The shaft is square in shape, big - maybe 9' X 9'.
posted by analog at 11:11 AM on February 15, 2013

This was a common construction practice for multi-family buildings, probably into the 20s or so. I currently live in a 1910 apartment building with a ventilation shaft that only has windows opening to it, and I've worked on a building (as an architect) with one section built in 1919 that had windows and vent shafts and another section built in 1940 that had something like the extraction system that pandabearjohnson describes. In the 1919 building, the shafts had covers over the top of them, but mostly to prevent precipitation/birds/etc. from going into them, and there was a significant gap between the cover and the top of the shaft so there was still ventilation - we were in the building on an extremely windy day and the shaft windows in many of the rooms were rattling even three floors down from the roof - I suspect your building is similar.

So, the vent shaft system works, and I've had good experiences with it in my apartment, other than that we normally close our shaft window during the winter, so the big drawback is that it doesn't ventilate if you want to be comfortable in cold weather. Modern extraction systems probably work better, but the system your old building has did just fine for a long time when no better option existed.

The principles you're working with are the stack effect and whatever force it is where air flowing across the top of a tube creates a vacuum in the tube and draws its contents out (I was thinking Bernoulli's Principle, but I'm not sure it's the exact thing here).

We have a similar situation but have tremendous vacuum from the ventilation ducts in the kitchen and bathroom (I suspect this is b/c other tenants have blanked their vents off).

Actually, there's probably a massive extraction fan sitting on your roof that's constantly pulling air out of your apartment. With this system, it's sort of silly to install ducts - I'm guessing you have radiators? - since the fan would just pull out air that your HVAC unit is pumping in.

So, having said all that, I'm not entirely sure what your question is though?
posted by LionIndex at 11:12 AM on February 15, 2013

Response by poster: Thank you, LionIndex, very helpful. As far as what I'm actually asking - I suppose that I am look for feedback about whether such an arrangement leads to an apartment feeling overly stuffy, hot, cold, mouldy, steamy, etc.
posted by analog at 11:32 AM on February 15, 2013

I suppose it could, simply because the ventilation system is easily defeated by closing the window. There's a definite difference in our place between having the window to the shaft open or closed.

In the 1940 building I worked on (originally a hotel), the vent shafts had ducts with grilles leading from the shaft to the bathrooms. On the roof, there was an enormous duct, connected to all the vent shafts. That duct led to a huge fan that was always on, sucking air out of the building. I guess it could be defeated by closing the vents, but it's far more of a constant system than relying on atmospheric conditions (unless the fan fails). As long as the fan works, you're getting humidity out of the building.
posted by LionIndex at 12:22 PM on February 15, 2013

Best answer: I lived in an apartment like that for about ten years. I found that while there was a skylight on the top of the shaft, it also vented to the outdoors, you just couldn't see it from the bottom of the shaft. I would bet that your prospective apartment is the same unless you know for certain it's not vented. (Also called lightwells) It successfully provided a cross breeze when windows were open. The only time it got stuffy was when there was no wind outdoors.

Even if it's not vented it will provide some air flow, because it will flow through the apartments of everyone else who have open windows on the lightwell. The downside isn't stuffiness, it's that many people will leave windows open, and it's probably brick lined, so you'll hear everything going on. (When it's the bathroom windows...) And, depending on the wind direction, you might smell everything as well.
posted by Ookseer at 10:44 PM on February 15, 2013

Yes, the right way for this to work is that the vent shaft pulls air out of your apartment and up towards the sky. The air that is pulled out gets replaced by fresh air coming in through the "real" windows. So if you can verify that the airshaft really is vented, then it should be no problem. If it really is sealed at the top, then you might have a stuffy apartment.
posted by gjc at 5:13 AM on February 16, 2013