Staircase pressurisation - open door
Staircase pressurisation - open door
(OP)
For a multi-storeyed building, how many "open" staircase doors do we consider while designing the staircase pressurisation system ?
HVAC68
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Staircase pressurisation - open door
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Staircase pressurisation - open doorStaircase pressurisation - open door(OP)
For a multi-storeyed building, how many "open" staircase doors do we consider while designing the staircase pressurisation system ?
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RE: Staircase pressurisation - open door
You'll need your country's fire code - there are lots of influencing design factors in this design - maximum pressure in the stairwell, max door opening force, presence of smoke stop lobbies, flow velocity through doorways etc.
RE: Staircase pressurisation - open door
The local code doesn't give any specific information about the number of "open" doors to be considered.
HVAC68
RE: Staircase pressurisation - open door
Same old song and dance.
Jabba
RE: Staircase pressurisation - open door
We have 4 staircases and 10 floors - that makes it 40 doors. We have considered 1 door in open condition in each staircase. But, no code details to support the above or otherwise.
HVAC68
RE: Staircase pressurisation - open door
However, when we were working in buildings each stairwell had its own fan system. Thus you would have 2-3 doors open in each stairwell.
I do not believe the intent is to assume that there would be only one door open in a stair at a time.
The fact is we worked on buildings from 35 to 70 stories, and there is just no good way to estimate how these systems work in a real life situation.
Do your best and pray that your system never has to work.
RE: Staircase pressurisation - open door
RE: Staircase pressurisation - open door
50 Pa is a great number for controlling pressure (and the standard in two countries I know) as it also coincides with the standard leakage airflow test pressure, meaning data is available for different construction types and much is written by people like Max Sherman at the LBNL.
RE: Staircase pressurisation - open door
There are 4 components which add up to the total air quantity requirement for pressurisation :
1. Stair volume x 10 Air changes per hour.
2. 3mm gap considered over the perimeter of each door and with a 50 Pa pressure difference, air quantity that would leak out is calculated. Formula based on ASHRAE.
3. Air that would leak out through wall cracks based on an average leaky building - again wtih a 50 Pa pressure difference. Formula based on ASHRAE.
4. Assuming 1 door completely open and with a velocity of 0.8 m/s.
I have added all the above and arrived at the total air quantity required for pressurisation of the stairwell.
The big assumption I am making is item no. 4 - i.e. one door open, for which I don't have any back-up in terms of a code, as my local code doesn't give enough information.
HVAC68
RE: Staircase pressurisation - open door
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Your own local code obviously takes precedence over this. As a life safety system, our design will need to be signed off by a PE so you may as well get the information up front.
Find out your normal infiltration ACH for the space, multiply by 20 for 50Pa ACH (refers LBNL model).
You probably don't need to run normal stairwell ventilation during fire-mode, and 10ach is a lot anyway.
RE: Staircase pressurisation - open door
IBC2006 no mention on the number of doors
NFPA92A - no mention on the number of doors
For UK BS5588 - ONE (Class A & C System)
TWO (Class D System)
THREE ( Class E system)
THREE ( Class B System)
For Canada NBCC - FOUR
For Australia AS1668 - THREE
For Singapore CP13 - THREE
However, certain door velocity is required for each recommended number of doors.
Eimreh