duct through T-joists

[Bob Cooper]

This isn't really directly 'workshop' related but i know you guys will have some thoughts on this. I'm building a room *above* the workshop while i'm building the workshop. The room above will have a kitchen with a downdraft vent. So i'm going to be bringing 6 or 8" round ducting through the floor and i need to traverse across (through) 4-5 joists. The joists i believe are called T-joists but they are the 2x3 w/OSB internal sections.

I talked to the supplier and they said i could cut 6 or 8" holes as long as i stayed away from the last 4' of the span...which is no problem.

I talked to my HVAC guy about doing this work and i'm not sure i trust his opinion. He's like to use some form of expandable flex pipe...which clearly tells me it's not smooth walled. I know it would be a lot more work to cut 16" or so lengths and connect them but i'm less concerned with the amount of work than i am 'what's the right way to do this'.

what's your thougts/advice? Thanks.

[Jim Andrew]

They are called I joists. My daughter sprung one of the downdraft vents on me, too late to run it under the floor, as the ceiling under it was already finished. We put it under the kick space of the cabinets. Was a real pain, but it worked ok. We used rectangle duct.