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Heating a well insulated small home with only electricity

Hoping someone can offer recommendations for our current heating situation.

We are building a very efficient cottage that will be lived in year round. We're having an issue on deciding how to heat the home. We will have a backup wood stove but I don't want to rely on the stove. The issue is we won't have access to gas, electric will be our only method for heating besides wood/pellet.

Specs:

1600Sqft over 3 floors including the basement

R40 Sip Panel Walls
R35 Basement Walls
R60 Sip Panel Roof
Triple Pane Windows
7kW-10 DC Solar System
South facing windows to receive passive heat in the winter.

The location is outside of Cochrane Alberta Canada.

We have looked into zuba mitsubishi heat pump and geo thermal. Both are expensive and we think it may be wiser to take that extra money and invest into a larger solar system to offset heating with convention wall heaters and baseboard heaters.

What would you recommend? Would electric infloor heating be an option? We looked into a electric boiler but they're really not that efficient.

Looking forward to replies.

Asked by DavidCalgary
Posted Jun 19, 2017 2:26 PM ET

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14 Answers

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1.

David,
If I were you, I would use one or two ductless minisplits. But the decision is yours.

If you want to install baseboard electric resistance heaters, the cost to install the equipment will be less, but the operating cost will be about 3 times the cost of operating the minisplits.

Answered by Martin Holladay
Posted Jun 19, 2017 2:39 PM ET

2.

The 99% outside design temp in Cochrane Alberta is probably at or below the -18F minimum guaranteed operating temperature of Mitsubishi equipment. Calgary's 99% temp is -17F, and Cochrane is 100 meters or more higher in elevation.

If mini-split, Fujitsu's AOU-xxRLS3H serious would be a better choice, since it has a published capacity at -15F, and won't automatically turn off at some temperature when it's dramatically colder than that. Some amount of auxilliary resistance heating may make sense in rooms doored off from the mini-splits, but doing 100% of the space heating with resistance heaters &/or the necessary amount of PV array to offset that us is probably going to be pretty expensive.

Getting a handle on what makes sense for heating equipment starts with an aggressive (not conservative) room-by-room Manual-J type heat load calculation at the 99% outside design temperature. You can reasonably use -28C or even -30C as an outside design temperature, but not colder than that unless you have the real weather data proving it. Use +20C as an indoor design temperature.

A guy in Quebec posting on this site under the handle Jin Kazama heats his place at -30C with four (3/4 ton?) Fujistu xxRLS2H series mini-splits, and IIRC his house is bigger than that. The 4 heads were necessary for heat distribution reasons (a 45' long hallway to the bedrooms, etc). In a compact 2 story + basement you can probably get away with one head per floor, and unless it's regularly used space it may not even need a head in the basement.

If aggressive load calculations weren't performed prior to getting quotes for the Zuba or ground source heat pump it's likely that the capacity of the equipment quoted was ridiculously high, estimated with a WAG based on contractor experience with code-minimum type houses.

Run the load numbers room by room, floor by floor and report back.

Answered by Dana Dorsett
Posted Jun 19, 2017 3:20 PM ET

3.

David,
I use the combination of a wood stove and baseboard heaters in projects quite regularly (apostasy! apostasy!).

It only makes sense if the wood stove is going to be the main source of heat, and the baseboards are for helping to warm distant rooms as well as providing backup heat when you aren't there.

The other caveat is that Alberta is a much colder climate than coastal BC.

Answered by Malcolm Taylor
Posted Jun 19, 2017 3:25 PM ET

4.

Malcolm:

"We will have a backup wood stove but I don't want to rely on the stove."

Seems David views the wood stove as backup-only, in which case one or two mini-splits probably makes more economic sense (with perhaps some right-sized baseboard for the doored off room loads) than doubling the size of the PV array to cover the additional power use. In most cases even an additional 3 KW of PV is going to cost as much or more up front as a pair of mini-splits.

Better than a Manual-J would be a BeOpt energy use simulation to see just how much of the heating energy use will be offset by solar gain.

A pair of Fujitsu 9RLS3H (one for each above-grade floor) can probably cover the load at -30C, and a pair of 12RLS3H almost certainly would. But without realistic heat load numbers to work from this is just a WAG.

With the large amount of south facing glass on a 2-story house at least one of the mini-splits would likely see a reasonable duty-cycle for cooling. It's a heating dominated climate, but with a 1% outside design temp of ~80F with a lot of clear-air solar gain there's going to be a real-enough cooling load too, even if much of the time it could be managed with convective night time ventilation.

Answered by Dana Dorsett
Posted Jun 19, 2017 5:52 PM ET

5.

I hope to get the heat load numbers this week.
Right now in our province there's a 30% rebate incentive on PV so that's why I fee the money is well spent, plus I will be putting this building with solar ect in a mortgage.

What's the average cost of a fujitsu installed?

I originally started thinking about mini splits but I will have many rooms with doors (4 bedrooms,3 baths, mud room, utility room) so I was thinking that I would have to install ether ENVi wall convention units or cadet baseboard heaters in those rooms)

Why is so hard to heat with electric. I grew up in Newfoundland and almost all the homes were heated with baseboard and wood stoves.

Answered by DavidCalgary
Posted Jun 19, 2017 6:17 PM ET

6.

David,
Q. "Why is so hard to heat with electric? I grew up in Newfoundland and almost all the homes were heated with baseboard and wood stoves."

A. I don't think anyone said it was hard. Installing electric-resistance baseboards is fast and cheap. All we're saying is that your energy bills will be three times higher than they would be with a minisplit.

If you will be mostly burning wood, who cares about the electric bill? Electric resistance heat probably makes sense in that case.

Answered by Martin Holladay
Posted Jun 19, 2017 7:02 PM ET

7.

David: costs will be pretty local, but for what it's worth, two years ago we had two Fujitsu minsplits (9RLS 3H and 12 RLS3H) installed for about $6500 total, in Maine.

Answered by stephen sheehy
Posted Jun 19, 2017 8:17 PM ET

8.

Dana,
I took that as meaning David didn't want to just rely on the wood stove - but I think your interpretation was more accurate.

Answered by Malcolm Taylor
Posted Jun 19, 2017 9:07 PM ET

9.

Ok I'll look into how much a mini split is tomorrow. I was looking on Fujitsua website and notice they have multi zone units good till -15F (-25C) I'm wondering is this the units I should be looking at? As they will run multiple heads off of one outdoor unit. I like the idea of their floor wall units, little less of a eye sore I guess. One it be best to run one in the basement main area and one on the main floor?

Basement 650sqft (2 small bedrooms/1 bathroom/1 utility room and play area for the kids 250sqft
Main floor 603sqft (kitchen / living room (18ft ceilings) mud room and half bath) high ceilings in the living room.
Second floor $349sqft ( 2 bedrooms and one bath, barely a hallway,more of a landing)

I find heat pumps aren't very popular in my province, remember when I was calling around looking for info on heat pumps and zuba it was amazing how many heating companies didn't have a clue what I was talking about. In a city of 1.5 Million there's only one contractor listed on Fujitsua website. I don't have much confidence in their recommendations or installs based on what I've seen. I'm glad I found this forum.

BTW
I will have a dual core HRV

Answered by DavidCalgary
Posted Jun 19, 2017 9:43 PM ET

10.

Question..Can mitsubishis heat pumps do to head units off of one out door unit?
Seems to me most companies out here don't install Fujitsu.

Answered by DavidCalgary
Posted Jun 20, 2017 10:46 AM ET

11.

Mitsubishi has cold climate multi-splits (multiple zones on a single compressor) too, but multi-splits are not necessarily the right solution.

In your location you may need backup heaters, since Mitsubishi units automatically turn off to self-protect at some temperature below -18F, which is roughly your 99% outside design temperature.

Multi-split versions have fairly high minimum modulation levels on their compressors, and a head per room is almost certainly going to be ridiculously oversized (to the point of lower efficiency) on the individual zones.

Only when you have the room-by-room load numbers will it be possible to figure out which rooms can be reasonably served by an individual head, and which rooms don't have enough load to work with.

The individual room loads of basement bedrooms are VERY small, but that makes serving them with a single mini-split head in the common area pretty easy, since the R-value of the partition walls is very low compared to the above grade exterior walls. It's really the window losses that drive the load in those rooms. Don't forget to subtract off 220-250 BTU/hr per sleeping human for the bedroom loads.

In my area cold climate mini-splits in competitive bidding usually come in under USD$4000 per ton of compressor, sometimes under USD$3500/ton, but it varies. Projects with multiple mini-splits are often cheaper than multi-splits of similar capacity.

Answered by Dana Dorsett
Posted Jun 20, 2017 11:54 AM ET
Edited Jun 20, 2017 12:03 PM ET.

12.

Do you have net metering in your area? I wouldn't rule out out elect baseboard or radiant panels. With your cold temps I'm not convinced that it would be a factor of 3 more expensive to run and you have good solar there. Plus, probably no one uses heat pumps there, and perhaps not much AC either (?), so the contractors won't have much experience

Answered by brad
Posted Jun 20, 2017 1:00 PM ET

13.

DavidCalagary

I don't have time this moment to go into precise detail so I will follow up later. I have done already what you are considering, ie resistance heat with wood stove backup rather than mini-splits. It is quite true that I am "overpaying" for my heat relative to propane, natural gas (unavailable) or mini-splits. Still my wife and I love the fact that the house is quiet with very minimal fan noise due to air exchange. Our floor plan is similar in being three floors and not at all an open floor plan. We are in a somewhat remote rural area at 8000' with approx 8000 HDD CZ6+ design temp -15F

Locally, minisplits are not favored or understood. Bids were almost as bad as traditional heating systems and service/repair costs looked like a potential nightmare. We would have required multiple heads and two outside units with attendant installation issues getting lines around. The occasional 24" snow events might choke out the units at inconvenient times. Our electrician tipped us off to radiant cove heaters they were being asked to install in many homes at even higher altitudes. Given the losses of fan efficiency at altitude along with the high front end costs, we decided to go with the cove heaters. Every room has its own thermostat so everyone is happy. Out particular climate situation makes it possible to do without A/C just by venting the house at night and closing up by day.

The insulation levels we have are similar to yours and the tightness (though not verified) probably lies under 1ACH. I will dig through some of the bills and try to be more precise on energy usage. I am a bit embarrassed to say the floor area we have is substantially larger, although in my green defense we designed for two generations which sadly is now one.

Bottomline outlook is I did not spend even a third of what the minis were bid at and I don't have to hear them, look at them, or maintain them. If a cove heater should ever crap out, I am only out one room not half the house and I can change it out in half an hour. Not sure what your electric costs are but we pay 0.15 per KWH out the door so to speak. It may sound like an idiot decision to have made, but we still like the result.

Answered by Roger Berry
Posted Jun 20, 2017 1:22 PM ET

14.

Roger wrote: "If a cove heater should ever crap out, I am only out one room not half the house and I can change it out in half an hour."

The only resistance heaters I've ever changed our, or heard of being changed out, was because they were tired looking or had paint on them. As long as you have power, you have heat. Another reason to use them in cottages that won't be continuously occupied.

Answered by Malcolm Taylor
Posted Jun 20, 2017 3:35 PM ET

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