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Which heating/cooling system would be most cost effective?

ttapley | Posted in Green Building Techniques on

I have recently bought a split 2000 sqft (3000 sqft including basement) duplex building that had been converted into a signgle-family home some years ago. I am in the process of converting back into a split duplex.
The current heating source is an oil-fired forced-air furnace which serves the whole building (one side better than the other). The building insulation is also way below code (R-5 walls, R-8 attic) Duuring this reno/remodel i am updating/improving all the insulation (R-14 walls, R-50 attic), improving airtightness and building envelope efficiency. I will be replacing the heating system as well, with two separate systems. I am trying to decide weather I should tear out all the ductwork and just go with a three headed mini-split (three levels including basement), or keep the ductwork and add an air-source ducted heatpump, or a wood pellet furnace (no cooling).
Since I will eventually be renting these units, cost is a large factor. But so is performance and efficiency.
Also, this is in a zone 6A area (southeast Canada), and I’m not sure if an air-souce heat pump could perform as needed in the colder times of the year. If so, What model?
Any advice or incite would be appretiated, thanks.

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  1. GBA Editor
    Martin Holladay | | #1

    It sounds like you are considering two fuels -- wood pellets or electricity. We can't determine which fuel is cheaper if we don't know your fuel costs. But you can do that math yourself. (Here is a link to an online fuel cost calculator: .)

    You will get better heat distribution with a ducted system than with ductless minsplit units.

    Ductless minisplit units will cost less to operate than a ducted heat pump.

    As long as you choose the right ductless minisplit units and size them correctly, you can definitely heat with ducless minisplits in your climate zone. Check out the specs to see their heat output at low temperatures before choosing which unit to buy.

  2. Expert Member
    Dana Dorsett | | #2

    The newly released AOU-15RLS2-H puts out 15,000BTU/hr @ -26C. It'll keep on going at an unspecified output at temps below that. There are two other (smaller) units in the xxRLS2-H series too.

    The Mitsubishi MSZ-FE18NA has similar (slightly higher) output at -25C, but turns itself off at -28C, but automatically restarts when it warms back up to -26C or so. There are other sizes in the - FExxNA series too.

    If temps below -27C are rare once every couple of decades (or more) events either series is fine. But size them for the heat load at your 99% outside design temp, not your absolute record-cold temps. If you're near one of the listed locations or between a couple of them you can probably come up with a reasonable estimate for a design temp. Note, the design temp is often several degrees higher than the absolute coldest temps in a year, but those colder hours are short-lived, and being shy a couple thousand BTU/hr for a couple of hours doesn't result in an egregious drop in temperature.

    What city/town are you in?

    A room-by-room heat load calculation is necessary to figure out if a ductless solution will really work for you, but it's worth running the numbers. If it looks like it will work, it's WAY more comfortable (and more efficient) than most ducted air heating & cooling.

  3. bobhol | | #3

    I am doing the same research in Peterborough On .My findings indicate Mitsubishi or the new Fujitsu H series will work down to-27 C . I will be using one on each floor of a 2 storey slab on grade of about 2100 sq ft I am waiting to hear what others have to say ...regards Bob

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