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Heating Conundrum: Duplex/Multifamily Conversion

Miq Member Posts: 1
I've just bought a 2000sqft split-level home that is essentially an over-under duplex on one electrical meter. The house (1976) is currently serviced by a 30+ year old oil-fired boiler via hot water baseboards. The house is split into two boiler zones, upstairs and downstairs. I will be putting 1-2 mini-split heat pumps on each level (approx 1000sqft each) as the main source of heating and cooling, but where I am in Nova Scotia, Canada requires a backup heating source. This is where I'm stuck. Below are my constraints/preferences:

1. I would like to separate the heating of both apartments onto their own electrical meter (the panel needs to be upgraded anyway)
2. I'd like to move away from oil, don't have access to natural gas
3. I'd prefer to keep the existing hot water baseboard system

How simple is it to split up one boiler system into two electric boilers if they're already zoned? What sizes would I need? What about propane boilers or pellet boilers?

Would it cost less to tear out the entire boiler system and install electric baseboards instead? (~$1500+labour)

All flooring in the house needs to be replaced, would electric in-floor heat be comparable? I found a deal on materials, works out to be $1000 for enough heating cable to do the whole house + 3 days extra labour.

We plan to install solar panels to offset the increased electrical use as electricity is expensive in NS.

Appreciate any help or guidance. Thank you!


  • Hot_water_fan
    Hot_water_fan Member Posts: 1,841
    Consider an air-to-water heat pump, which would use the existing baseboard. You can easily incorporate resistance or oil backup in that configuration. 
  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    First off, unless your available space for solar panels is huge and you have favourable feed in tariffs for your electricity -- or the money for BIG batteries -- forget the idea that the solar panels will offset the added electricity use from the mini-splits, never mind any other electric heat such as electric boilers. It won't. It won't even come close.

    The first thing you need to do then is figure out how much power you really need to heat the two units. A heat loss calculation. That will tell you whether you even have a hope of a radiant floor being adequate; I doubt it will be, but it might be if the building is really tight and not too exposed. Radiant floor or not, it will also tell you how much power (BTUh) you will need to supply for each of the two units.

    Since you want to get away from oil, which is the cheapest of the various power options, you are really left with one choice: LP gas, which if I recall is expensive in your area but will do the job. Since you want to split the costs of heating, your best option is going to be a mod/con boiler for each unit -- probably the smallest size available, but your heat loss will tell you that.

    There is, by the way, a good reason why your Provincial regulations require a backup heat source: the Powers That Be, for once, recognize that heat pumps can't do the job in your climate.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • GGross
    GGross Member Posts: 1,043
    Electric baseboard will be the cheapest to install, and most expensive to run, unless you can produce your own electricity.

    Good mini split inverter heat pumps will be reasonably expensive to install, and very efficient to operate. pair with electric baseboard as a backup heating for the really cold days. You get cooling with this option. There are also cheapo mini splits that many people DIY, mileage varies here. Some people have few issues, other get the bad units.

    Electric boiler will be about the same expense to operate as electric baseboard, install here kind of depends on the system, probably a bit more to install than the baseboard, equipment cost will be more, no coooling

    Air-to-Water Heat pump. This can work great, finding installers and service companies familiar with the product would be my personal stipulation on this. Probably a similar install expense as the mini split system, you will also need some sort of backup with this in extreme cold climates, I believe many use a resistance electric heating when the heat pump portion can't keep up. Very efficient when running in heat pump mode, same cost to run as the electric baseboard when running off resistance heating. You won't get cooling from this unless you also install an air handler or something other than baseboard to provide the cooling.

    With any electric install, sizing first, then equipment selection, then make sure you have the available power to run the equipment.

    Personally if I were you I would look at mini splits with backup electric baseboard. or air handler style mini split system with a back up electric heat strip, but that would require installing ductwork which may not be easy to do in an existing building.

    Sizing may be done several ways, but not just based on the square footage of the home. Either a manual J or historical fuel usage can help determine sizing for heating, a manual J will give you a cooling load as well when done correctly.
  • Steamhead
    Steamhead Member Posts: 16,832
    @GGross , do people really need A/C that far north? I doubt it.

    @Miq , as others have said you need to look at operating costs. You may find that oil is the most economical option. In that case, two small oil-fired boilers would be the way to go.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • GGross
    GGross Member Posts: 1,043
    Steamhead said:

    @GGross , do people really need A/C that far north? I doubt it.

    @Miq , as others have said you need to look at operating costs. You may find that oil is the most economical option. In that case, two small oil-fired boilers would be the way to go.

    I made the recommendation as the homeowner stated they want to get away from oil. I live in an area that is actually further north than Nova Scotia and every new construction is getting A/C here these days. It is not a necessity by any means, and I don't have it. But we generally still see a few 90 degree days, which is enough for some people. I prefer not to assume what others have as a budget to work with and instead follow what they tell me they are looking for.