Our house plans are finished and I'm working on the details. I'm struggling with the heat system and would like some opinions. I know I need a heat analyses done, but is there any chance of a 80 gallon electric water heater heating the following house in Alberta? House is 2200 square feet is well insulated with 4" rigid foam under the basement slab and ICF to the roof with R-40 roof insulation. The reason I ask is natural gas is too expensive to hook up and I'm trying to avoid propane. Most heat will be supplied with wood so this be a backup while away. Thanks for the feed back.

Yes, you really need to first determine the heat loss BTUs and then see if the electric water you are considering can provide them. It sounds like you have a well insulated building, but you are in a cold climate too. I prefer to avoid speculation and I recommend that you run the numbers. BTW, we have free DIY heat loss analysis and hydronic radiant floor heating design software on our website if you are so inclined to do this analysis yourself. I also recommend that you consider using an electric boiler specifically designed for hydronic radiant heating too...and please don't install an open loop system.

Electricity isn't exactly free in Alberta either. Heating primarily with mini-split air source heat pumps, with resistance heating in the doored-off rooms that would otherwise have comfort issues (this can be determined by the room-by-room heat load) would cost less than half what it would to heat with an electric boiler. There are several models that have a rated output capacity at -25C, a temp at which they're using only slightly more than half the power of resistance heating delivering the same BTUs.

But it all starts with the room by room, zone by zone heat load calculations. With ICFs simple I=B=R methods doesn't do justice to the peak-shaving you get out of the thermal mass. Modeling it with DOE2.2/BeOpt for both climate and site factors would be better than a dumbed-down Manual-J, etc. (DOE2.2 and BeOpt are freebie downloads from the US Department of Energy, but they have climate datasets for many Canadian locations.)

Like wood stoves, mini-splits are point-source heating, but since they're fully modulating, with maximal efficiency at part-load, they play nicely with wood stoves or other heating. But if your electric heat is truly only a backup for when you're away, electric baseboards are probably going the be the cheapest way out from an up-front cost point of view.

Yeah, I would certainly agree that good modeling is the right approach, but Manual J is certainly better than putting your thumb in the air and whistling...

There are locations where wood and electricity are the only energy that is available. Wood and electricity (PV and hydroelectric) are often the only forms of renewable energy that can be harnessed at a property site. Once you have electricity, it is extremely easy to convert it to BTUs with very little energy loss. So using electricity should NOT be considered a less than green approach and the cost of using it can vary from much to zero.

Depending who gets their way, either our masonry heater or our hydronic radiant floor heating system alternate as being the backup to our passive solar. I prefer using the masonry heater as backup and just using the hydronic radiant floor heating system to keep the floor comfortable. We are blessed in that both our masonry heater and the hydronic radiant floor heating system use renewable energy solely harnessed from our property. The cost of our wood is our labor and the cost of our electric is our PV/hydroelectric system maintenance cost which is nil. We very much like mini-split heat pumps, but not enough to trade the comfort provided by a hydronic radiant floor heating system to a home having a 100% slab floor that would be cold otherwise. Slab-floor based hydronic radiant floor heating systems have a high ROI and a slab floor is pretty much required if you get aggressive about passive solar heating, so the overall design tends to favor this approach and the overall ROI is excellent too. We would certainly recommend electric baseboard heaters in lieu of under-floor hydronic radiant floor heating systems, but we fully appreciate and understand that some people are willing to get the comfort provided by a hydronic radiant floor heating system at any cost.

I think I will try the DIY heat analysis and check out the electric boilers. One of the problems I have is the electric company tells me on my bill that I pay 10 to 12 cents a KW for electricity but when I divide the amount of the bill by the KWs used it works out closer to 35 cents due to all the taxes, riders blah blah...Natural gas is the same way. I will have a look at the air source heat pumps also, didn't know they made them.

Posted By Paul W. on 29 Nov 2013 04:10 PM
I think I will try the DIY heat analysis and check out the electric boilers. One of the problems I have is the electric company tells me on my bill that I pay 10 to 12 cents a KW for electricity but when I divide the amount of the bill by the KWs used it works out closer to 35 cents due to all the taxes, riders blah blah...Natural gas is the same way. I will have a look at the air source heat pumps also, didn't know they made them.

All electric companies do that. The kWh might be 10 cents but by the time you add their connection fees, taxes, surcharges, metering, delivery, line maintenance, etc, it comes out much higher.

With me fees all added up it comes out to around 15 cents per kWh.

 

Dana is correct (as is nearly always the case) that boilers are less efficient and will have a higher utility cost to operate than mini-split heat pump approach. However, I don't know if the difference is as extreme as Dana indicated. Furthermore, an electric boiler will be more efficient than a hot water tank and electric boilers are relatively simple devices that should have less maintenance issues and associated cost over their lifetime than a mini-split heat pump. There is hardly ever a simple, always perfect solution. You first need to select the road you want travel and then pick the best hardware for the journey.

Sailawayrb, I used the heat loss calculator on your website and came up with an BTU/hr loss of 79,058. Does that sound about right?

That seems rather high to me, perhaps by a factor of 2 or 3. What did you use for your design temps, areas, R-values, floor perimeter (i.e., you need to enter exposed floor perimeter and NOT floor area for a slab floor), volume and ACH (or CFM)? You indicated that your ceiling is R40, your slab is likely about R20, and your ICF walls are likely about R25 plus R3-R6 to account for mass effect in your climate. I don't have a clue what your fenestration area is or what your fenestration U-factor is (which you need to inverse and enter as R-value).

Paul - You did not mention where in Alberta. Design day temp vary a bit across the province.
Our house is also ICF and around R65 ceiling insulation. It is a 2 storey with walk out basement heating 6200 sq. ft. We did heat it the first two years with two 40 gallon heaters but with all four elements wire in. Most water heater just us one element at a time. When the top one is satisfied then they switch to the bottom one. They are designed for storage of hot water not high heat load.

We are just east of Calgary, our design day temp is -32C and our heat loss is 52,000 so yes, I think your calc's are a little high.

A few years back we switched to Enmax for our power and signed up for five years @ .08 cent. The previous year we peaked at .18 cents with Epcor.

We are now on propane with a 50,000 btu boiler. Agreed that Atco has got very greedy on the instals. Time to go back to rural Co-ops. The one just north of us usually doesn't even charge for the hookup.

Air to air or air to water heat pumps even designed to get to lower temperatures than old air source heat pumps offer no less than a 2 to 1 savings over electric boilers on the coldest days and quite a bit more in less extreme weather. Geothermal can take that number even higher, but quite a bit more up front cost is required. Regardless of heat plant or fuel, design your radiant floor for the lowest operating temp you can. This is most efficient with many heat plants.

I don't see how a 2200' ICF house in Alberta can be bumping on a design heat load of 80KBTU/hr with the windows and doors closed. Even with only single-pane windows it would be hard, but without higher performance windows, the windows are likely to be the biggest single load factor. Pay attention to ventilation rates when using load calculators- they typically default to numbers that are way higher than reality (even for a stick-build, let alone an easy-to-air-seal ICF.), which can skew the numbers upward by 10,000BTU or more. If you are ventilating primarily with HRV, and only when necessary, from a practical point of view you can set the ventilation rate to zero for load calculation purposes.

At -25C the ductless mini-splits that are designed for those temps are running about 1.8x more efficient than an electric boiler or water heater, but at -15C it's about 2-2.5x as efficient, and it only gets better from there. That is probably colder than your binned hourly average in January unless you are way up north or at high altitude- even Edmonton's mean temp in January is a cozy -10C. A part load and higher temps they can do quite a bit better. See the bench-test info of a couple of popular units here: http://www.nrel.gov/docs/fy11osti/52175.pdf

FBBP, Im in the foot hills East of Jasper so I would guess our climates are real similar (its milder here than most other areas due to the Chinook winds we get) I say that and we just had -35C, talk about chilly!

I looked into the mini-splits but Im a little leery of multiple compressors. I used to work as an engineer on the ocean and spent a whole lot of time dealing with a/c's and reefer/freezer units.

Here are the numbers I originally used 20, 75, 353, .32, 3176, 25, 75, .5, 2000, 40, 3, 70, 15, 2220, .35ACH

I will go back and try with no air exchange and what that does for my heat load.