This is a little simplified, but not too much. I have architects and plans for a a two story house plus a basement. The house is about 80 feet by 20 feet with all stories extending the whole footprint. The floors between stories are supported with a 20" floor truss system.
I was told the floor truss system could pass HVAC ducts. I thought this would mean that the floor of the 1st story could provide HVAC for the basement and first floor, and the floor of the 2nd story would provide HVAC for the second story. All mechanical would be in the basement with a chase between the 1st and 2nd story.
Instead they want to serve the 2nd story from the roof (there is no attic) by adding roof trusses for ducts. And add a 2nd story mechanical room. This is wildly inelegant to me.
Since I insisted on keeping the mechanical in the basement, now they've designed a chase from the basement all the way up to the roof of the second floor. Possibly even more inelegant.
Will the 20" floor truss system not provide the space to service 3 stories from two floors? With a zone for each story?
If it doesn't provide adequate space, should I look at mini-split for the basement, hydronic floors for basement, or some other type of solution for one or more floors? It'd be nice to avoid having HVAC in the roof, right?