Heat Pump Webinar – Q&A Summary

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Q: Answers regarding the efficacy with respect to keeping a home warm in Ottawa’s climate would be appreciated.  I am two degrees separated from people who had/have one in this climate, who maintain they don’t work.  The husband is an engineer, so you’d think he knows what he’s talking about.  But it’s unclear how old their system is/was…..maybe it’s an older one, and newer installs work better?

A: There are high-performance cold-climate versions that can maintain their full capacity down to very cold temperatures, below -20oC for example. These often have electric resistance back-up as a “just in case” when it gets extremely cold. It is also possible to back-up the heat pump with a gas furnace if someone was hesitant to go all-electric. In that scenario, it is still possible for the air-source heat pump to do the vast majority of the heating (depending on how it is sized).

Q: How much home insulation do you need for a heat pump to be effective? I live in an older home and it is not possible to insulate the walls.

A: It’s always good to insulate and air-seal when doing a heat pump retrofit, but it’s not necessarily a requirement. My own home is heated with a heat pump and I also have no insulation in the walls. It works great.

Q: We have heard that for larger homes the heat pump may well not be able to do the job and a back up is needed, either electric or gas. If that is right, how do the two systems interact? Do they share the same distribution system for instance?

A: If the home is centrally ducted then, yes, both the back-up and the heat pump would distribute the heat through the ductwork of the home. With gas back-up it is typically either/or – you use the heat pump or the gas back-up. With electric-resistance back-up it can work at the same time as the heat pump with the electric resistance “topping up” the heat from the heat pump.

Q: I want to make sure the hybrid to -30 will actually work in Ottawa

A: With hybrid systems there is a gas furnace as back-up. If it is sized right, then it can heat your home down to as cold a temperature as required. In hybrids, the ASHP is typically off in extreme cold but since extreme cold is rare over the course of a year, the heat pump can still do the large majority of the load.

Q: I realize there will be differences between various brands and models of heat pumps, but in general, at what temperature do most heat pumps need assistance from a secondary heat source (e.g. electric strips or gas).

A: This really depends on the heat loss of the house and the capacity of the heat pump. When sized properly to meet the design heating load, cold climate air source heat pumps do not require back up to -20C and beyond.

Q: It would also be great to hear about the feasibility/cost of installing in & heating older era homes (i.e. 1960s) with ground heat pumps vs. air heat pumps in colder areas (I am in Ottawa). Here is an example from Edmonton: https://www.cbc.ca/news/canada/edmonton/energy-efficient-house-edmonton-1.6641320

A: You’ll see some examples of installs in 100-year-old homes in the talk. Both ground-source and air-source heat pumps are great options. Which is best for the homeowner will depend on the homeowners needs and the home itself.

Q: Can you address how effective they are when temperatures goes below -35′?

A: I have yet to see a manufacturer claiming effectiveness down to -35oC. The leading brands can go down to -30oC. I think when it gets that cold you will need back-up. Either a gas furnace or electric resistance heating.

Q: I’m looking to buy a cold climate heat pump right now. Just a few Qs for those with one: Do you feel warm on cold days in your house?  How loud does it get during the winter?

A: I switched from a gas furnace to a heat pump and feel warmer on cold days than I did with the gas furnace. Here’s why: https://www.energyvanguard.com/blog/heat-pump-or-furnace-which-is-better-for-comfort/

Most of the other questions will depend on the size and type of system and how it’s installed and controlled. Wall-mounting is not recommended from a noise perspective.

Q: I’ve started the process of converting to the heat pump technology for heating, air conditioning and hot water tank. One concern that I’ve come across relates to the refrigerant used in heat pumps. Some research shows that it can be hundreds of times more polluting than CO2, methane and other GHGs in the eventuality of a lead as the heat pump system ages. Are any of the heat pumps available in Canada using HFC free coolant?

A: Yes current refrigerants are terrible for global warming potential BUT there isn’t a lot used and if installed correctly, they shouldn’t leak.  Studies have shown that behind the meter gas leaks have more climate impact than refrigerant leaks.  For my home, my estimates are that if all refrigerants were to leak, it would have the same climate impact as two years of gas furnace operation.

The Federal Government is in the process of approving new refrigerants in accordance with the Kigali Agreement.

Q: How many times per day will a cold climate heat pump go through its defrost cycle during the winter months?

A: It depends on the outdoor temperature and the defrost control algorithm. The heat pump defrost most around 0oC because the air still carries a lot of moisture, and the moisture is what causes the frost. When it gets very cold the air doesn’t have moisture and does not need to defrost. The heat pumps which use smart defrost control algorithms would not need to defrost very much when it gets very cold.

Q: In older homes, how important is upgrading insulations, windows, and air sealing before conversion to ASHP?

A: These measures reduce the amount of heat that your home needs and if enough is done, you can install a smaller (and cheaper) heat pump system.  However, significantly delaying installation of a heat pump because of planned building envelope upgrades isn’t always the best choice for emissions.

Q: Is it true that with a heat pump it is recommended that you do NOT turn down your thermostat at night as much as you might be used to doing with a gas furnace?

A: That is true. Heat pumps are most efficient when they do not have to make up a large set back. We recommend only turning down the thermostat if the home will be unoccupied for a longer period of time or if you like it a little cooler when you sleep.

Q: Is an ASHP significantly more efficient than an air conditioner for cooling?

A: It depends on the heat pump and on the A/C you are considering. Most people have low-SEER  A/C in Ontario (13 SEER). A good heat pump can be higher than that. A cheaper heat pump may be comparable. Note: SEER is an efficiency measure.  The higher the number, the more efficient the unit.

Q: What’s the life span of a heat pump.

A: Natural Resources Canada says 15 to 20 years. Similar to an A/C.

Q: How reliable are Hybrid systems?  Control systems are much more complicated than old tech. Can set points we changed to favor lower gas vs lower electricity costs?  Is this automatic?

A: We have been installing hybrid systems for years in areas that don’t have natural gas and people rely on propane, for example. The systems are reliable when properly installed. The control systems are more complicated than a simple thermostat but they are no problem for contractors who install them regularly. The balance point can be adjusted in the thermostat install settings and some thermostats will do this automatically to optimize operating cost.

Q: Are there options for mid-rise apartments with baseboards?

A: Yes. If you have a balcony then a split system is possible. If you don’t have a balcony, then monobloc options are possible, which duct air in from the outside. See the resource library on sustainabletechnologies.ca

Q: Any case studies on installation of a HP in older double-wythe brick home without wall insulation (and without a wall cavity that could be insulated)?

A: The STEP case studies looked at these, check them out here: https://sustainabletechnologies.ca/home/heating-and-cooling/air-source-heat-pumps/smarter-home-heating/

Q: Are heat pumps going to add much benefit to a modern new well insulated home with an electric forced air system, and with an A/C attached?

A: Your system is rare. My understanding is that there are few electric furnaces in Ontario. An air-source heat pump would cut the electricity required by space heating by up to a factor of 3. See https://www.cleanairalliance.org/an-analysis-of-the-potential-for-air-source-heat-pumps-to-reduce-energy-costs-and-greenhouse-gas-pollution/



Q: If your heat pump ices up, is it important to de-ice it?  How do you do that safely?

A: Heat pumps have an automatic defrost cycle – like your freezer. Most manufacturers turn off the indoor fan and run the unit in reverse to use the heat of compression to warm the outdoor coil and melt any frost or ice. It is important to ensure that the outdoor unit is located at least 30 cm above the expect snow level to allow them to defrost properly.

Q: I’d love to hear the experience of others in heat pump maintenance companies/contractors. These would be for annual cleaning of indoor heads and outdoor inverters. Not just the filters on indoor heads…that’s easy. Thx

A:  I run a co-operative of HVAC contractors in Ontario. We recommend annual maintenance including cleaning the indoor and outdoor coils. For ductless split units, there are tools that maintenance techs can use to make this easier than it used to be.

Q: The place most likely for us to install the outdoor unit is subject to a fair bit of snow drifting – is this an issue?

A: Installing the outdoor unit in a place where it will get covered in snow is a real issue. If the bottom of the outdoor coil comes in contact with a lot of snow, the snow will melt during defrosting and refreeze into ice. That ice can destroy the fins on the coil and even crush the tubes, causing a catastrophic failure that is not covered by the warranty. Make sure the unit is installed where it will be above snow drifts.

And always keep pets away from the outdoor unit. Dog urine can quickly destroy the equipment!


Combining with radiators/in-floor heating

Q: We have a hot water baseboard radiator system. Is it possible to use an air-to-air heat pump? Would we need to upgrade all our radiators to operate at around 40 deg C

A: Air-to-water heat pumps exist, but you’d need to speak to a professional to determine if this is a viable solution for your house. There’s a bit more info on this topic here: https://nationalpost.com/life/homes/the-hot-new-way-to-heat-a-home

Q: Can heat pumps be used in older residences that have radiators (circulating water in a closed system) as their means of heat distribution?

A: Yes, there are air-to-water heat pumps available but this gets a little complicated in an existing hydronic system designed around high temperature radiators. It is currently more common to add air-to-air heat pumps aka “ductless splits” to homes with baseboard heating and leave the boiler in place as a backup.

Q: Can air source heat pumps be used for hydronic with in-the-floor water pipes.

A: There are air-to-water heat pumps available. These systems are on their 3rd and 4th generation in Europe and Asia but haven’t made much of a splash in North America yet. Expect more manufacturers to bring them to market here in the next couple of years.

Q: Could an air-to-water heat pump be used with an in-floor heating system?

A: Yes. In-floor heating is actually ideal for air-to-water. Much more so than homes with radiators. The key point is that the infloor requires warm (not hot) temps and this is easier for a heat pump to manage.

Q: Given that air-to-water heat pumps are largely unavailable in North America, what do you have to do in an old home with radiators? Do you have to have the “cassettes” on the wall? Would you need them in the basement, too, to keep the floors warm? (floors are currently heated by the water pipes leading to the radiators).

A: There are air-to-water heat pumps available in North America, and even a couple of Canadian manufacturers – Arctic Heat Pumps and Nordic Heat Pumps (not a recommendation though – just pointing out they are available). The challenge is to get it to work with existing rads which require high temps. You can replace the rads with low-temp versions. Or you can just get a ductless air-source heat pump (and forget about the pipes for the boiler). There are also high-temp heat pump options that may work with your rads – I’ve seen this with geothermal but not air-source. Hybrid options where gas takes over in extreme cold are also available. If you have in-floor heating then it is generally easy to do an air-to-water heat pump because lower temps are required.


Installation issues

Q: Would be great to hear your thoughts on the need to upgrade to 200 amp service. Also expected costs for Hydro to do their service upgrade, and electrician to do their work

A: I live in a townhouse and have 100A that cannot be upgraded to 200A. It’s looking like I can get a 2-ton cold-climate version to meet my full needs, but after that I may need to choose between electrifying my hot water and getting electric resistance back-up for the heat pump. It depends on the heat loss of the house and the other loads in your home. If your electrical service was constrained, a hybrid system utilizing a heat pump with gas furnace back-up is possible. It would require less space on your electrical service panel.

The service upgrade cost varies on whether it is an overhead connection to the transformer or in conduit. It also varies on the distance between the electrical meter and the service panel. In the GTA I’ve seen costs at $3k (included a panel upgrade as well) and up to $6k.

Q: For people who have a recently installed high efficiency two stage gas furnace, does a dual fuel system and adding a cold weather heat pump still make environmental and economic sense?

A: Adding an ASHP to an existing high efficiency furnace makes a lot of sense. Gil will share information about hybrid systems in the webinar.

Q: Can heat pumps be installed where the source of fuel is from an oil furnace?

A: An air source heat pump can be added to an oil furnace but the federal government just announced an additional grant starting early 2023 for an oil-to-heat pump conversion program as part of the Greener Homes Initiative. I suggest looking at this program when it is fully unveiled.

Q: How far apart can the inside and outside units be? My current air conditioner is about 3 meters from my furnace. I’d like to keep the indoor and outdoor units in the same places as my current system.

A: The minimum distance between indoor and outdoor unit is usually 3-5 m but it depends on the manufacturer.

Q: Are there potential issues with having an oversized ASHP? Ideally, one would do a deep efficiency retrofit (e.g. increase insulation; ensure continuous air-vapour barrier; high-efficiency doors & windows; etc), but many people end up replacing their HVAC when their system breaks down.

A:  It is important that when you size for the heat load that you don’t cause problems for cooling in the summer. Most cold climate air source heat pumps have inverter compressors and can run at partial capacity. The important thing is to ensure that the minimum cooling capacity is lower than the design cooling load and that the existing ductwork can accommodate the air flow needed for the heat pump.

Over sizing heat pumps for heating can lead to several unintended consequences. 1) Impaired cooling and dehumidification in summer can lead to mould growth in humid climates and breathing problems. This is less of an issue with 2-stage or modulating equipment but it needs to be confirmed that the system can modulate down low enough in cooling mode that it isn’t oversized. 2) It needs to be confirmed that the duct system can move the required amount of air for the heat pump running in heating mode. If this is not considered, the system will be loud, and the high air resistance (external static pressure) will impair the efficiency of the blower motor and lead to premature failure.

Q: Does the Air Source Heat Pump replace your furnace or is it an add-on?

A: An air-source heat pump can fully replace a furnace. Or it can replace your air-conditioner and work with your furnace – that’s called a hybrid system. The air-source heat pump would turn off when it gets extremely cold and the furnace would turn on. If sized right, the heat pump can still do the large majority of the heating.

Q: I have been told that I need to upgrade my 100amp Electrical service in order to install a cold climate heat pump with electric resistance backup for really cold days (below -30c). Unfortunately, I have also been told that no one on my street is able to upgrade at this time.  What measures are being taken to allow those of us with 100amp service to switch to a cold climate heat pump so that large portions of the population do not face this roadblock?

A: I’m in this situation. I am in a townhome in Mississauga. Depending on where you are full electric back-up may not be required. Alternatively, you could choose a hybrid and back your system up with a gas furnace. It requires fewer amps. If you size it right, it is possible for the heat pump to manage the large majority of your heating.

Q: Heat pump hot water tanks blow cold air into the room they are located in. Not everyone wants cold air blowing in those rooms.

A: Manufactures will dictate in their installation instructions the recommended minimum room size for a heat pump water heater to avoid over-cooling the room. This is typically between 700 – 1000 cubic feet (ie. 10’x10’x7′ or 12’x12’x7′)

Q: I was told that my “basement” in my heritage home was too low for a heat pump. What are the space restrictions? Would a hybrid system fit in a low ceiling “basement”?

A: You will need at least 84″ of ceiling height to install a central ccASHP in the upflow position. There are horizontal installation options available, and we have installed them in crawl spaces as low as 48″

Q: What is the difference between single-stage and two-stage HPs?

A: Two stage heat pumps will better cool in the summer because they allow you to size for heating need without over cooling. Fully modulating inverter heat pumps are becoming more popular because they can ramp up and down more effectively.

Q: I just installed 2 wall-mounted Mitsubishi hyper & regular ASHPs. I constantly hear varying motor sounds/bass rumbles throughout the house, which differs from what I keep hearing about heat pumps being quieter.  Have you encountered this with wall-mounted vs ground-mounted heat pumps?

A: Vancouver has a great gu