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Community and Q&A

Are minisplits not allowed as the only heat source?

climb_on | Posted in Mechanicals on

We are in Minnesota (Zone 6a). Building this summer on 12 acres. 2200 sq/ft single level (maybe a bonus above garage), slab on grade.

After speaking with the first HVAC company, they claimed that the LJ’s would not allow mini splits as the primary heat source in a home. I would have to install baseboards, in floor heat, etc. They said I would be required to have a heat source in every room. I got the sense they were trying to sell me on radiant, which I have learned, I can comfortably avoid if I insulate the slab well (they also disagreed with that).

Does anyone know, or heard of mini-splits not being allowed as the primary heat source? I have found nothing in my searches to suggest that, but want to get some opinions before I talk to the next company.

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  1. Anon3 | | #1

    Code may require a heat source in each room, to satisfy code, people just buy $15 heaters for each room to show to the inspector.

  2. climb_on | | #2

    If a heat source in each room is code (is that in the IBC?), that may or may not fly here. I could see them requiring something more permanent like a hardwired baseboard heater. Not surprisingly, the HVAC guy I talked to didn't put it that way or suggest that as an option.

  3. Expert Member


    I don't know much about your codes, but when this topic came up here in the past I recall someone saying they used these as approved heat sources in each room.

  4. Westhawk39 | | #4

    Ive been fearing this in Manitoba where I am building as well. After some further discussion I don't think Im opposed to baseboard heaters in each room. I think even if turned off most of the time, would allow you to increase the temperature of a bedroom on extremely cold days as perhaps with the bedroom door closed for a period of time the room may cool down… thats my thoughts anyways.

    I am looking foreword to seeing how dramatic the temperature gradient will be in a highly insulated 1000 square foot house with central heating source.

  5. climb_on | | #5

    I tend to agree. I don't think its a bad option. It's gives a reliable backup heat source, as well, if the primary source goes down. I'm a little surprised I can't find more examples about how folks are handling this though.

  6. brp_nh | | #6

    We have a single ductless mini split on the lower floor of our two story ~ 1500 sq ft (gross) house in zone 6a of New Hampshire. That is all we use 99% of the time, but we do have hard wired Stiebel Eltron wall mount heaters in the bedrooms, bathroom, and a couple downstairs for backup. I don't think we were required to do this. I remember just checking off the box for "electric" whenever we had to specify the heat source on permit applications.

    I thought I read in another thread that the code isn't that you have to have a heat source in every room, but that the heat source needs to be capable of heating every room to 68F, but I have no idea if that's correct.

    Malcom posted the link above...if you run into issues with inspectors/etc., just put an extra 120v outlet in each room in a good spot for one of those Convectair wall mount heaters, that should satisfy any requirements. And hopefully you can get away without buying one...or just get a couple for outlying rooms.

  7. JC72 | | #7

    I haven't, but I'm sure you weren't thinking of just one mini-split.

  8. climb_on | | #8

    I'll do what is recommended by the installer, but yes, I assume that will be 2 units and at least 1 of them will have multiple heads.

  9. Expert Member
    Dana Dorsett | | #9

    Codes based on the IRC typically require that all occupied rooms be capable of being automatically heated (no space-heaters) to 68F at the 99% outside design temperature. In a high R house it can be possible to hit that mark with a mini-split even if the rooms are doored off, but even when the math proving is shown it can still be a hard sell to the inspectors (or mortgage bankers). In a zone 6 climate it's going to take a building envelope well beyond code minimum to hit that performance point.

    With an aggressive Manual-J load calculation installing the minimum amount of resistance electricity "backup" for each room may be necessary. With a favorable floor plan (or a ceiling with utility chases) it may be possible to get there with a mini-duct cassette providing heat to doored off rooms. But to meet code the extended temperature capacity tables for the mini-splits must cover the load at the 99% outside design temp, with a 68F indoor design temp. Very few mini-splits have a specified capacity below -13F, which may or may not cover your 99% outside design temperature.

  10. swazo | | #10

    I too am building a high performance house in Minnesota and plan on using mini-splits. I plan on using a masonry wood stove for most of my heat when I can justify starting a fire. This doesn't satisfy code as Dana explained. I met with the city inspectors and they agreed that this plan would be approved if I have either hydronic tubing in place in the basement floor and tile areas on the main level or wiring to supply electric baseboard heat in the future. Both of these options seem reasonable. They don't require me to buy an expensive boiler or the eclectic baseboard that I would never use.

    I hope this helps.

  11. climb_on | | #11

    Jim, so which option are you going to go with? What city are you in?

  12. swazo | | #12

    I like the hydronic but question if I can justify the cost considering the low heat load. I still need to price both the wire runs and pex cost. At this time I'm thinking both. I can install the hydronic tubing myself in areas that will be cement anyway (garage, basement and tiled) and if I don't need a larger electric service box, the wire "shouldn't be that expensive".
    I just spoke with the city a few days ago and they liked the mini- splits. They were reluctant to approve this plan but went with it. This was a big hurdle for me and I don't want to throw them under the bus. You can email me if you like. jrsweazey@gmail .com. I would like to talk to you. I'm sure we could both benefit with sharing ideas.

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