High Rise Stair Pressurisation

[MechEng001]

I am designing the stair pressurisation for a building of 37 stories. I am using a set of fans at the top of the building and a set of fans at the bottom. I am going through a review process at the moment and have been told that generally for a building of this height we should have a 3rd set of fans in the middle of the building say level 16 or so.

I have done my calcs and they all seem to add up so I don't see why it should work with just top and bottom feeds. Mind you I have never done a building of this height so I cant confirm that it works in practice. Has anyone had experience using only top and bottom feeds with a building of this height?

 

[317069]

For sure your building has an elevator, is there set of fans in the top, bottom or mid of elevator shaft.

 

[MechEng001]

We have an elevator, but there is no requirement to pressurise the elevator shaft on this project.

 

[marcoh]

All depends on how you have sized your shafts. I have done similar buildings with one set of fan and worked fine. Control of multiple fans can become a much bigger issue, especially when trying to maintain acceptable door pressures.

 

[MechEng001]

I have sized the shafts to include ducts to prevent air leakage and have sized ducts at 6.5m/s. Is there a particular velocity you would use with a single fan? do you generally use ducts or simply push the air through the riser without ducts?
Cheers for the help!

 

[marcoh]

6.5 m/s should be fine and using a concrete shaft is fine and no need to metal duct. Normally the fire stair is within a concrete core so use the concrete core for 3 sides of your riser and construct the wall between the stair and riser. Therefore any leakage will be into the stairs. I would not be comfortable blowing air in at the top of a 37 storey fire stair without a shaft, it is in the region of 150m high