A few years ago I designed a home where the home owner wanted in-floor heat and air conditioning. It was a good size home and the homeowner did not want to provide space for large ducts. It was decided to go with a high velocity system. As far as energy savings, it was not an issue for my client. The home was built in Michigan and my client was from Massachusetts.

Its a complicated comparison. Here's an article with a good discussion that followes.

Thank you, RES! That is a helpful article.

I have no experience with the systems you mentioned. If you do go with one of these you need to find an HVAC contractor who has experience installing them properly.

How many stories is this home? Does it have an attic and basement or crawlspace? I am not a fan of running duct work through an unconditioned attic but it is something to be explored.

Could you build a chase that would blend into the architecture? There are creative ways to hide ducts. In a new design there are always possibilities.

I have always used hydro-air systems that supplied air to the first floor from the basement and to the second floor from a conditioned attic thereby avoiding structural conflicts. I have only used a high-velocity system in a historic renovation.

The house is four levels, including the finished basement. The attic level is a mix of cathedral and flat ceilings. All mechanical space (and all systems) are *inside* of the envelope, in conditioned space. The mech room is central on the attic level, and the other mech room is at one end of the basement, in a relatively long, narrow house.

At the urging of our architect, we had the HVAC contractor and architect meet with a structural engineer meet to discuss the ductwork and all the runs as they would relate to structure. The end result is being able to run everything the way we’d like. (We’re doing radiant heat with ducted A/C).

Excellent idea! Too late, however.

We faced similar issues with our build (http://bamasotan.us/2018/11/decisions-decisions-and-ducting/) that sounds like a similar 4 level with lots of steel and LVL's to yours.

We did have a meeting with our Builder, HVAC, Architect, and structural engineer to work out these issues. Many issues were worked out (replaced an LVL with steel to allow ducts to get through, changed truss spacing, etc.) but some things didn't get resolved in that meeting that they still needed to work on and everyone said that they would. We talked about a number of alternatives but the trade-offs were all such that sticking with standard forced air was the better decision. We do have in-floor heat (minimal cool if needed) throughout the lower level in addition to forced air.

We were quite unpleasantly surprised to find ducts run up a corner of our dining room and through my master closet. We had a couple of meetings to look at alternatives but in the end the recommendation was to keep them and work around them. I'm still quite concerned and unhappy about what impact this will have on the dining room and the loss of space in my closet.

The only other 'issue' is that one of the HVAC systems is located above my closet and so nearly above our master bedroom. We were assured by the HVAC folks that they'd be able to isolate everything enough that it'll not bother us with noise or vibration when sleeping. I'm quite nervous about it but for now am relying on their word.

* BTW, I didn't look over the structural drawings in much detail but was quite surprised when framing began that there were trusses over non-structural walls. Typically this is avoided (and usually not difficult to avoid) since it creates problems for getting HVAC, plumbing and sometimes electrical in to those walls.

Thanks, MiniSplit Heat. In fact, since I originally posted, I actually have been looking at some cassette-type units. Our architect mentioned that one of his projects had used a cassette-type unit mounted in a closet ceiling (they dropped the ceiling in the closet), one per floor in a relatively large house (ours is fairly large, too, so I would expect the same). He explained that on each floor, there was ducting from the cassette unit to the rooms on that floor. That sounded like a good option to explore. However, I am having trouble figuring out what I'm looking for, when I am searching online for more information/ideas.