GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Looking for recommendations on new HVAC equipment, hot water and heat load

hb1 | Posted in General Questions on

My house was built in 2008 and the HVAC and Hot Water Tanks are original and looking for guidance on new equipment.  I added a photoelectric roof top solar system last year that generates about 90% of my electricity on annual basis excluding my hot tub and 1 electric vehicle that I own.

Background Details:
1. Located in Calgary, Alberta, Canada – cold climate zone 6
2. House is currently is heated via 2 forced air single stage high efficiency natural gas furnaces (90,000 btu /hr upstairs and 110,000 btu/hr main floor) and also  in concrete slab radiant system that is heated from 1 of the 2 power vent water heaters for the basement which is fully finished.   My guess is they are completed oversized.  My house will almost heat with the radiant basement system and the 2nd store furnace and keep the main floor comfortable.  Historically I have consumed about 225 GJ of gas per year for home heating, hot water and cooking (gas stove & oven) with my oversized, inefficient HVAC equipment.  As well, I have 1 ac unit on the upstairs furnace.
3. The house is about 1,800 upper floor, 2,200 on main floor and 2,200 sq foot in the basement.  Per the house plans, 2 x6 wall on 16 inches R20 insulation; R40 roof insulation and it was built in 2008.  The house did have an Energuide home audit prior to putting solar on it.  The Energuide would put it (due to thermal bridging of 2×6 I believe):

  • Roof: R-38.5
  • Basement Walls: R-10
  • Slab: R-6
  • Main floor and Upper floor walls: 16.3

4. I believe heating in cold climate zone with heat pumps is next to impossible, or yet financially impractical in terms of capital cost  unless your house is insulated to net zero standard for when it gets really cold here  ie – 35 C nights.  Also, I would be concerned about my electrical connection being only 150 AMP from using all heat pumps.  I don’t think our grid can support heat pumps and electric cars yet and if the grid power is made from natural gas then using electric resistance heating does not make sense to me and is a bankrupt theory.
5. As carbon taxes rise in Canada, we maybe forced to heat 2 ways ie with heat pumps and back up natural gas systems for when it gets really cold. 
6. I have been researching new heating systems and looking at the following:
– fan coil heating from a boiler: negatives –  seems like a more complex solution, very few people that understand fan coil heating and fan coils now cost similar prices to gas furnaces – brands of fan coils include Hi velocity and I-flow and boilers such IBC, NTI, Viessman or combi such as Noritz or Navien; seems likes you very dependant on your contractor to make a fan coil work versus a out the box system  Postives: seems easier to implement 2 heat sources ie 1 large air to water heat pump and 1 large boiler 
– modulating or two stage gas furnaces combined with air sourced heat pump such as Daikan or just modulating / 2 stage furnaces from Lennox or other brands or even combi fan coil furnaces from NTI or Gradient 
– also considering putting in a Rheem 65 or 80 gallon heat pump water heater which could reduce by natural gas consumption by 20 to 25 percent and take advantage electricity generated from my solar system.  The other advantage is will use waste heat from my mechanical room which also has freezers in it so it should run very efficiently. 
– I have also researched air to water pumps.  The negatives seems like you buy them online and you are on your own to find an installer.  Also, you need a very complex system of buffer tanks.  Seems like if you have a problem, you will be on your own as it will difficult to hold accountability to the manufacturer or contractor.  Also, it seems like its difficult to find people in this area that have put this systems in when references are asked for.
7. I do like the current piece of mind of having multiple heat sources in case of equipment failure which to me is another negative for a 1 boiler heating system as problems always occur during holidays or while traveling  when its super cold outside.
8. When I read posts from people such as Dana Dorsett on sizing boilers its become very confusing on being under or oversized and it shows how little work HVAC contractors do in sizing equipment.  Early failures of boilers or ECM fan motors on modulating furnaces will negate any energy savings and cost you way more in the long run.

Based on some quick calcs with my r-values and info I found, the heating load with fresh air requirements is 93 500 Btu/h or 27.4 KW and the cooling load with fresh air requirements is 29 071 Btu/h or 8.52 KW.  Does this make sense?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Akos | | #1

    I know Calgary can seem cold, but it has a 99% outdoor design temperature of -24C (-11F) which is well within the range of modern hyper heat air source heat pumps.

    I would run through the calculations here to figure out what you actual load is at and we can go from there:

    Replacing the two existing furnace units with right sized heat pumps is fairly straight forward. The floor heat would be more of a challenge. Heat pump option for that is $$$, your best bet is a standard resistance boiler.

    With two heat pumps plus some floor heat of some kind, I think you would have backup heat well covered.

  2. hb1 | | #2

    The Daikin air to air heat pumps only match with the natural gas furnace as they don't make an air handler. The other system I looked at was air to water heat pump with low temp fan coils however as I mentioned they are sold online but not by local companies and you need to find an installer. My guess is this will change over the next few years. It can get below - 30 C in Calgary a 3-4 times per winter.

  3. Expert Member
    BILL WICHERS | | #3

    It's a common misconception that houses need to be superinsulated for heat pumps to work. That's like saying "houses need to be super insulated if you want to install a tiny furnace and still be warm". The solution is to use a bigger furnace, just like you can install bigger heat pumps (or more of them). Heat pumps don't REQUIRE lots of insulation to work, although more insulation allows you to use a smaller heat pump just like it would allow you to use a smaller furnace.

    What heat pumps do NOT do well is cycle on and off to maintain a temperature set point. Heat pumps like to modulate, providing a relatively small amount of heat ALL the time instead of providing a relatively large amount of heat PERIODICALLY to maintain a target temperature. Heat pumps don't like setback thermostats for that reason, and would rather hold a steady temperature all the time. Heat pumps are not as good at quickly bringing the temperature up, either, for the same reason. Aside from those minor issues that are easily dealt with, heat pumps don't require anything unique in the home.

    I don't think I'd consider a boiler unless you already have a hydronic system, or if you plan to use a wood fired boiler as a potential alternative heat source. Using an air to water heat pump just to run a water to air heat exchanger in an air handler doesn't gain you anything, and greatly complicates your system, probably adding additional inefficiencies too. I would not consider this option unless you are thinking about using a wood boiler as I mentioned above.

    I normally don't recommend heat pump water heaters (HPWH) in heavily heating dominated climates since they scavenge heat that you had to use fuel to make anyway. In your case though, you may be able to recover enough of the waste heat from those freezers to make things work out overall, but keep in mind that that same 'waste heat' would otherwise being helping to heat your home if you didn't use it to heat hot water instead. If the room with the freezers tends to be uncomfortably warm, then an HPWH might be a good way to make the room more comfy while using that excess thermal energy to do something useful.

    Consider adding exterior rigid foam if you can. 2" of exterior rigid foam would increase your wall's effective overall R value by over 50%. This would help you regardless of what you end up using as a heat source. Note that if you have large amounts of glass, you'll have less overall benefit.

    I would look into adding to that attic insulation if it's loose fill, since that's cheap and easy to do. Consider going up to R60 or so. Look into air sealing too, you can almost always find ways to improve on that. I'd look into the upper level ceiling (can lights, attic hatches), and rim joist areas as low hanging fruit here.

    You didn't mention the size of your home, but your furnaces sound oversized to me too. My home is about 4,000 sq ft and I have two 80,000 BTU furnaces. It has to be very cold in winter before I need both furnaces to keep the place warm -- usually one furnace alone is plenty. I would say right now I have 'moderate' levels of insulation, which I've been gradually upgrading as I move through with my renovation projects. Your home is likely better insulated right now.


  4. hb1 | | #4

    Thanks for your response Bill. I updated my house square footage #3. My sense is that adding a lot of heat pumps is impractical financially and a better solution would be heat pumps for most days with gas backup for when it gets really cold is probably the right track as it can get below - 30 C a few weeks a year. What brands of heat pumps do you recommend? I do have a radiant heating in my basement. I think its the main reason for my heating efficiency as it provides most the heat for the house with the 1 upper floor furnace adds heat at night. My main floor furnace only ran about 20 hours last winter.

  5. walta100 | | #5

    If you are connected to city gas the chances are your rates are low enough that installing a heat pump is unlikely to make economic sense especially if you will still have other gas appliances and paying the monthly connection fees.

    The only way to really know is to do the math using your rate / solar install costs.


Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |