Controling stack effet

[genieconseil]

Hi All,

I'm in the process of designing a 50 storey residential building. My question is the following:
How do I control the stack effect in the top of the stairwells and on the top of elevator shafts? I was thinking of installing a releif mortorised damper at the top controled with by a differential pressure sensor to open the damper when the pressure is hi?

I have individualised each appartement in terms of fresh air intake and for the evac of clothes dryers, kitchen hoods and toilet to reduce shafts.

Any advice on the smoke managements in the strairwells as well?

Thanks

Genieconseil

 

[genieconseil]

Wow! Doesn't anyone have any comments to my questions? Has anybody ever designed very tall buildings? Am I in the right forum??

Genieconseil

 

[BronYrAur]

I don't have experience designing high rise buildings, so I just offer a few comments.

I think the damper idea will make the situation worse. A damper creates a wide-open path for the air to travel. Stack effect is caused by buoyancy differences between the inside and outside air temperatures. Technically, in the hot summer, there is reverse-stack effect which drives air down. The temperature differences aren't nearly as extreme as in the winter, so you don't notice the reverse effect.

The building lobby is the most likely place for cold air to enter the building. Pressurizing the lobby will help keep that cold air out and help reduce stack effect. So introducing a large amount of heated OA to the lobby will probably help.

 

[GT-EGR]

Controlling stack effect can be accomplished in two ways that I know - seal the “stack” as type as possible. And you will still always have some effect, so if you want direct control of it you should supply pressurizing air into the stairwell - then at least you are controlling the source of air coming in, and get the ability to condition and filter it.

Smoke control is separate but related - you need to have a smoke management plan for the whole building - this can be done by pressurizing compartments like a stairwell as an area of refuge, or exhaust big open areas like an atrium. There are many small variations of putting a fan at ground level or roof level and ducting it through stairwell to discharge air every 3 or so floors. Your pressure target does have take stack effect into account, in addition to managing leakage as well as not making door opening force too extreme.

 

[michaelwoodcoc]

Really this needs to be tacked from all sides. Building design & mechanical design.

Tight building envelope would help
presurizing the stairwell
using vestibules, or one door after another where there are doors
using revolving doors for main entrance at the bottom

some questions:
does the stairwell have open well? that is, imagine a spiral staircase with empty space in the middle where air can flow up and down
is the building design already complete, and all that's left is mechanical?
how high is the building in relation to surrounding buildings? (I ask because of solar heat gain)
how far is the building from other said tall buildings in the area? (you can do math for days)
residential

It is my understanding that the stack effect is largely due to air buyancy, or different air densities. Including but not limited in respect to the outside air
If air can't enter or leave the building, it's really reduced. Key points are top and bottom, although every point matters
reducing air stratification should be possible with fans(air pear for example) and very careful design, keeping density the same, consistent temps from top to bottom, etc.
CFD analysis is probably a surefire way to come up with some good solutions

what is the primary means of tenant/ owners heating and cooling their places? Imagining they all have their own thermostat, and no vestibule, it could be a little more difficult with doors opening and closing, I'm sure. Air their entrance doors straight off the stairs? what does a typical floor layout look like?

what type of HVAC is their going to be? water source heat pumps? minisplits? what do you have to work with? I'd imagine some mitsuibish city multi units, with a ceiling cassette at the very top of the stairwell, for example, could help (CFD could tell you for sure) bit they have a max height difference of about 90 feet depending on models etc. and it's a 50 story building, not sure where you'd put multiple outdoor units. if water source heat pumps, it'd probably be hard to hide those things to condition the stair well and get a pretty uniform density throughout. Is it a chiller and boiler setup? probably not as building owners don't like to pay for tenant heating and cooling. Although when I had an apartment in Montreal, heating was included. Cooling, no. This was an older building with radiators.

I can't remember the names and specific details of all of this stuff so forgive me if I'm mistaken, but in hospitals and some gulfstream buildings there were lots of small units, that had variable speed fans. I think most were chiller/boiler. I can't remember much about them, really. But they seemed common in multi story buildings and I'm curious if you remember the name.

Positive pressure in the stairwell is probably a good idea to help eliminate smells from tenants places getting in there. Negative pressure where needed.



Really, we could talk about this all day, and all week without knowing some more details about building design and how much flexibility you are given, and the desired client setup (tenants pay bill or building manager)
are there going to be stacks, I guess, for dryer vents? bathroom exhaust vents? kitchen hoods? how luxurious is this place? Where in the world is this place?

I ask because in some parts of the world, it's a mess, but tenants supply their own ductless mini splits and sometimes even take them with them when they move. One look at the outside of these buildings and you can call them snowflake unts. No two units alike

Sorry that's so long. I have very limited design experience on this but I did have the benefit of speaking with some engineers and getting training from manufacturers and vendors when we did design bid builds.

more info is deffinately needed.



Engineering student. Electrical or mechanical, I can't decide!
Minoring in psychology