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HVAC for architect-designed new construction in MA

January 12, 2019

We have a fabulous design, from an aesthetic point of view, and ample mechanic room spaces top and bottom, but of course there are a couple of steel beams and several massive LVLs involved, and a few other features that make it challenging to figure out ductwork. We are looking seriously at a Zehnder ventilation system, and a Unico high-velocity cooling system. (Heating will be all hydronic radiant.) I am curious if any [semi-]professionals on this site have experience with considering a high-velocity/mini-duct system in new construction, and why you did or did not favor that option. We put the Unico cooling system in our current house some 14 years ago, and I know it is louder than other options. However, we might be willing to accept that in exchange for less trouble with ducting. I would be especially pleased if I thought it was an energy-saving option, as well - I have seen hints of that possibility. We are building (GC'ing ourselves) a fairly tight house, with a great deal of attention to appropriate barrier layers, sealing, limiting penetrations, insulation, European-style windows, etc.

Thank you!

Comments (11)

  • PRO
    Mark Bischak, Architect

    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.

    caseyb thanked Mark Bischak, Architect
  • PRO
    caseyb thanked RES 3d Sketches
  • caseyb

    Thank you, RES! That is a helpful article.

  • mike_home

    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.

  • PRO
    RES 3d Sketches

    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.

  • caseyb

    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.

  • doc5md

    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).

  • caseyb

    Excellent idea! Too late, however.

  • opaone

    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.

    caseyb thanked opaone
  • MiniSplit Heat

    The benefits of cassette air conditioning units.

    · Based on the fact that cold air falls, cassette a/c units which are mounted on ceilings ensure that the air is well distributed in the room. These air conditioning units have very powerful fans which can ensure that air is circulated in a larger space compared to other air conditioning units.

    · Because cassette air conditioning systems are usually mounted in the ceiling, basically floating or false ceiling, cassette a/c units do not consume essential space.

    · The condenser of the cassette air conditioning unit is typically located outside the building. As a result, a cassette a/c unit doesn’t make any noise, and this makes it the perfect choice for businesses and residential buildings.

    · Another benefit of a cassette air conditioner is its programmable thermostat and variable speed fan. This means that the user can adjust the room temperature, which helps in saving electricity bills.

    caseyb thanked MiniSplit Heat
  • caseyb

    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.

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