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Next few weeks I will be in the process of getting quotes for mini-split HVAC system. Curious, if anyone has gone ductless and if so, how is that working out?

The house will be a a two story build(Buffalo area): main floor with an office and a living/dining/kitchen, and a 2nd floor with 4 bedrooms and 4 bathrooms. We will be insulating the foundation, the attic and spray foam the cavities. There will be two fireplaces(master bedroom and living room) that will be actively utilized during winter. All bathrooms will have heated floors and towel warmers.

By looking at the drawings It looks like 8 head mini-split should be sufficient to cover the whole area: 1 head x each bedroom(4), 1 head in the upper hall(cooling lower hall too), 1 cassette in the dining/living/kitchen area, 1 head in the office and 1 cassette in the basement.

Few areas of concern are:

Heating: Given that last few years have been somewhat cold in Buffalo, how good are heat pumps w/mini-slits at keeping the place warm? I've been reading that heat pumps may not be a way to go if outside temperatures are below -15c.

AC/cooling: What would be the best way to cool the bathrooms? Besides proper ventilation, cold air from the heads wont have direct way into the bathrooms so I am a bit concerned with not having a "sauna" during +35c days. I think an air handler or a ducted mini split zone may be a solution for the smaller spaces?

Electricity: how much would such system consume comparing to conventional forced air HVAC systems?

We'll do a heat load calculation before going any further but I just wanted to get some head start and some input.

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    As far as the bathrooms, if I were planning it, I would assume that the ventilation fans in the ceilings of the bathrooms would pull in enough conditioned air to keep them at an acceptable temperature. The fans should be on timers so they could be run for 15 min after a shower. So I would specify superior quality and capacity ventilation fans. And the bathrooms might require electric resistance heaters. – Jim Stewart Aug 13 '18 at 11:55
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    Buffalo NY is surely a heating dominated climate. Are builders there putting in mini-splits for heating as well as cooling? Our 1970 tract house in Dallas TX has an a/c duct in each of the two bathrooms and this really clears the bathrooms of excess moisture. Since the 70s the trend in Dallas for "value builds" went away from ducts in the bathrooms. Our ceiling units contain exhaust vent with fan, a light, and a heat lamp with fan blowing on it. Our original units are still in place and functioning. The fans are not on timers. – Jim Stewart Aug 13 '18 at 12:10
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    Other than the extreme cold I would use ductless mini they are very economical to run. Do you have gas available? For heating with the extreme cold gas beats just about everything except a geothermal heat pump for cost to run but geothermal is more expensive to install. These are some of the things I would ask about or discuss with the hvac company's that will be quoting the job. – Ed Beal Aug 13 '18 at 17:07
  • How well are you insulating this house? Heating loads fall off much faster than cooling loads as you insulate and air-seal, so the practicality of this depends mostly on how good your envelope is at keeping the warm stuff in and the cold stuff out. Also: are you open to hydronic heat as an alternative to forced-air if some sort of fuel-fired system is necessary? – ThreePhaseEel Oct 27 '19 at 22:17
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I recently had the same question when building a home in N. Alabama for a relative. I asked all local HVAC contractors about it and they all recommended against it for two reasons. 1) cost 2) reliability. They stated their typical installs require replacement in 6-8 yrs. They did state, however, that they were a good option for things such as small additions or bonus rooms above garages where upsizing the main system would be difficult or expensive due to additional ducting requirement. I am surprised any heat-pumps would be sold in climates as cold as yours. They might maintain temps but I am certain one would never truly feel warm in a heat-pump heated home with temperatures THAT cold. Here in the deep south, I set my dual-fuel unit to switch to propane at ~30 deg. I would freeze to death if that cut-over were at -15!

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