question about the TJ joist in wood apartment

[lzh007]

Normally we put all duct in bulkhead along the wall in apartment building. I know it looks ugly if the ceiling is not high, but it will comply with the fire requirement.
While sometimes the owner request to put duct in the joist space. My boss seems not willing but accepts whatever. I want to know if it is allowed or not to utilize the joist space for HVAC? If so then any method to keep the fire rate of the floor (or ceiling)?

 

[walkes]

You cannot use the joist space as a return air plenum. If the ductwork is within the fire rating all penetrations should be protected with fire dampers. You could use duct firewrap on the ductwork within the ceiling (essentially building a bulkhead around the duct with fire resistant material. Confirm fire ratings with the Architect.

 

[buzzC2]

I believe in some jurisdictions the joist bay may be wrapped with sheetrock and fire taped so there is GWB on 3 sides and open on the bottom. If the joist space doesn't end at a rated wall, you would need to have the end of the channel sheetrocked/taped. The duct would then be placed inside the sheetrock lined joist bay.
That MAY eliminate damper requirements.

 

[gparker6]

Which is a better joist I-Beam or Truss