I would keep the in-law suite separate. I don't know what your plans are for the future, but if you ever sell, having them connected could be a major drawback for the new owners. I can't think of any benefits, to having only one system, but can find several drawbacks, such as cooking smells, etc.

As for the HVAC, how I'd break it up depends on your climate. If you have a really warm climate, then I would use 3 units, one for the suite, one for the bedrooms and one for the rest of the house, especially if the house has two floors.

I'm in S. FL, so getting the house properly cooled is high on my priorities. Heat is optional down here.

With that, it doesn't make design sense to do ductless, and it doesn't make cost sense either, probably. The only reason I can see to do it is that there are sometimes tax credits or rebates. Your contractors might be pushing it because of profits/ rebates or because your design doesn't allow for ducts.

I would do traditional HVAC systems - probably 3 given what you have described as a two story space (2 units) and then a separate in-law suite not connected to the main house as a unit. Mini-spits are loud and they are really ugly, IMO. Using zone controls to attempt to heat/cool separate spaces with one unit is not done much in our area any longer. The professional HVAC companies here are saying that zone controls never worked well and never met the expectations of the homeowners so they no longer do them.

I think MA really confirms the need for not ductless. You have several months of below freezing. Even here in Oregon they recommend backup heat, and we only have several days of below freezing weather.

I think ductless are great for certain things. When your choice is electric baseboards or cadet heaters, obviously ductless is better. When you have built out a new space like a garage or a basement or an upstairs apartment or a small studio or shop they make great sense compared to redoing all of the HVAC. But in a new build, full size house, it just seems like you'd be picking a compromise choice for no reason.

I would do two units in MA. One for the main house, and one for the in-law suite.

You mentioned that you'll have a wood stove, which will warm the main house up a lot, and cause the heat not to come on. The in-law suite would end up freezing, while the main house might have a window cracked, because it's too warm.

A traditional HVAC unit with ductwork will allow for better airflow throughout the houses. Plus, traditional AC units tend to cost less, both in initial costs and also when repairs are needed.

cashsheatingandcooling.com

CJ M.

curious - liked your post, but why do you say ductless is clearly better?

"think ductless are great for certain things. When your choice is electric baseboards or cadet heaters, obviously ductless is better. "