Best Way to Heat a Ductless Multi-Level Home

Question

I just bought a home and it desperately needs an update to its heating. It currently has baseboard electric resistance heaters in every room. There is no duct-work in the house. We're in cold humid climate with expensive electricity (Ottawa, ON, Canada). The house is 2 levels + basement:

Central heating isn't out of the question, but I'm under the impression that retro-fitting duct-work would be prohibitively expensive/big job, and I like the idea of zoned heating to minimize wasted energy (and$$) as much of the house will be un[der]used. Eg, the office only needs heat during the weekdays.

These are the options I'm aware of:

• Install duct-work and central gas furnace,
• Install cool-climate multi-head ductless heat-pump to heat and cool the most used rooms (up to 4 heads I think?),
• Install gas fireplace heating (possible locations shown on floor plan),

The question is: a) what other options exist, and b) what combination of these (or other suggested) options can be installed to provide the best heating solution. "Best" will be defined as the solution that minimizes costs over 10 year period while maintaining a comfortable 20degC on the main floor and master bedroom.

As a starting point: my thoughts were to install a gas fireplace in the lounge and create a vent in the adjacent wall to blow cold air at the fireplace from the kitchen-dining room. That should add some needed circulation. Then install a heat-pump to handle the guest/master bedrooms and office. The rest would keep the baseboard heaters.

Answer 1

(Note: my experience in answering this question is from around 2010-2011. As far as I know, advances in the technology since then make my answer even better, but I can't guarantee that.)

You need to do the math on the equipment purchase prices, installation labor costs, maintenance costs, and energy costs of any system you choose, but I would look very closely at your second option (what you call "multi-head" and around here we call "mini-split").

Benefits:

• Control every room separately to maximize efficiency.
• Minimal modifications needed to install, just running the power and the refrigerant pipes.
• Lots of different sizes and styles of unit to fit any room.
• If there are a few rooms for which it makes sense to condition them to and there is room to run a few ducts, there are some "combination" units which have the guts of a regular "ductless" indoor unit but are meant to be installed in an attic or crawlspace and ducted into the rooms. (Based on your floor plans, I'm not sure whether you need this or not, but it doesn't hurt to know that it exists and a local dealer/installer can help you figure out if it is right for you. It could be perfect for covering your entire second floor with a single attic unit.)

Also note that you can get more than four "heads"/zones from a split unit. For example, Mitsubishi makes some outdoor units that support up to 8 zones and Daikin makes some that are up to 10. Of course, remember that each indoor zone unit is going to add cost to your project.

The one issue you might have with a Heat Pump system is with the outside temperature - many systems are rated to function well down to around -20 degrees C. According to my quick search, your average winter low temperature is around -15 C, which should be fine, but there are occasional dips down to -25 C every few years for a day or two. That said, and installer or dealer in your area will know more about what models are designed your climate.

As others have suggested, under-floor hot water radiant heat is also very nice, but it is likely a lot more challenging to install, especially for your second floor since the floor and the ceiling below are finished. It might be easier on the first floor if your basement ceiling is unfinished though.

Answer 2

I'd look at heated floors. The idea is you lay a special wire mesh on the floor, then a compatible surface is installed over it. The wires maintain temp at the set point and natural convection works in your favor to circulate the air.

Answer 3

This is a great question but it is broad and I don't think there's really a definite answer.

Installing duct work really depends on more than whats shown in the floor plan sketches you have. Depends on the basement, the attic, and whether there is an place you can build a chase from attic to basement. There are small high speed systems that work with smaller ductwork that may be worth looking at.

Depending on the floor joists, and how open your basement is, under floor radiant heat may be an option for the first floor.

Heat pumps have an efficiency advantage over baseboard electric, especially in mild weather, and they are easier to install, but you have to have wall space for the cartridges. Open floor plans are an advantage. The best thing about heat pumps is you get air conditioning as well.

Look hard at your cost per BTU with all available sources (propane / natural gas, baseboard electric, heat pump). But also look at the cost of installation, the maintenance cost, and the life cycle. Furnaces don't last as long as they used to. Baseboard is IMO the longest lived, and near zero maintenance.

Answer 4

If you have gas available I would consider 2 smaller gas furnaces. One in the basement and one in the attic for heat. This eliminates the need for a main trunk line and return going to the other floor. I am a proponent of mini splits unless in a area that has gas and colder winter temps because the need of aux heat or electric resistance heat to supplement the heat pump at cold temps. By placing 2 smaller gas furnaces the basement unit can heat the ground floor and the basement. A smaller unit in the attic can heat the upper floor. I suggest this because gas is so much cheaper but if you also want AC some of the high end mini splits do work into the single digits but the savings on duct work and the space lost from the main trunk and return is the reason I would suggest 2 smaller gas units for heat. Added to cover op comment. I have installed and have a mini split that works into the single digits. My current home is quite a bit smaller than my last by almost half but my heating costs more (similar insulation values) the units do work but consume more power when the temps drop into the low 20's and below. Mini splits do have the advantage of AC but if I had gas in my area I would have gone that route. One advantage to gas if you have power outrages is it only takes a small generator to keep the furnace going this can be a big advantage in cold climates, currently I supplement my heat with a pellet stove if I loose power I fire up the generator to keep lights, stove, water and the fridge going. If I needed to power the compressor it would take a much larger generator. I do like my mini split easy to controll the different zones but the operating cost is higher than gas.