All About Heat Pumps
The heat pump is a basic component of home energy efficiency upgrades. Whether your priority is greater home comfort, lower utility bills, or fighting climate change, the heat pump is something you should definitely consider.
What Exactly Is A Heat Pump?
A heat pump is a remarkable piece of equipment that can heat and cool a home using very little energy. First invented in the mid-1800s, heat pumps move heat from one location to another in the same way as our fridges, freezers, and air conditioners…but the heat pump that you install in your home can move heat in two directions. In winter, it pulls heat out of the air or ground outside and moves it into your home, while in summer, it takes heat from your home and moves it outside. Because it simply moves heat from one place to another, it uses much less energy than systems that burn fuel to create heat.
Why You Should Make The Switch?
Many of the first people to adopt heat pumps were motivated by concern over the carbon pollution produced when we burn fossil fuels like fossil gas (traditionally referred to as ‘natural’ gas to enhance its public image). More than half of Toronto’s greenhouse gas emissions come from buildings, and most of those are generated by the fossil gas burned to heat them. The desire to reduce greenhouse gases and to be kinder to the planet continues to be a major motivating force, but people are starting to recognize the other advantages of heat pumps.
Are All Heat Pumps The Same?
The short answer is no. They all use the same principle of moving heat from one place to another, but the place they get the heat and the way they distribute the heating or cooling can be different. Some homes may even use more than one type of heat pump.
Most heat pumps in Toronto are air source heat pumps (ASHP), meaning that they obtain their heat from the air. Within this category, you will hear of regular or conventional heat pumps and cold climate heat pumps (ccASHP), which are able to gather heat at lower temperatures.
Conventional ASHPs are adequate for milder climates like Vancouver. For a Toronto home, they may also be sufficient for a very well-insulated house, if paired with another heat source like your existing gas furnace in a hybrid system (more on this later), or if you really like wearing sweaters.
Cold climate heat pumps are a bit more expensive than conventional heat pumps due to their more-complex design, but their higher efficiency leads to operational savings in the long term. They are probably the best solution for most Toronto houses, and the only ones you should consider if you want to get off gas completely.
You may also hear about ground source heat pumps (GSHP), which get their heat from the ground. These devices are relatively expensive and require considerable ground space for heat collectors. For this reason, they are impractical for most private Toronto houses and are not the focus of this discussion.
The second thing to look at is how the heating or cooling might be delivered. In Toronto, most houses have either ducts or radiators. Prior to heat pump technology, in ducted systems, air has been heated by a gas furnace or cooled by an air conditioner and then moved through the house in ducts usually hidden in walls and ceilings. A house with radiators has used gas to heat water in a boiler, and the hot water has been distributed through the house in pipes and radiators. A radiant system also uses hot water to heat floors and/or ceilings. A shrinking number of houses still use electric baseboards for heating without ducts or radiators.
If Your House Has Ducts…
If your house has ducts, you will probably want to continue to use a ducted system to distribute air heated or cooled by the heat pump. You will likely have a central unit that serves the entire house. The condensing unit of the heat pump will be installed outside either on a raised platform or attached to an outside wall (like a conventional air conditioner). An air handler inside, where your gas furnace was, will circulate the warm or cool air.
If Your House Has Radiators or Radiant Floor Heating…
In this case, you have two choices:
If you want to keep your hot water distribution system, you can opt for a “hydronic” system. Homes equipped with boiler systems and radiators or radiant floor heating can use an air-to-water or, less frequently, a ground-to-water heat pump system. The water circulating in these systems will be at a lower temperature than with a boiler, which may, sometimes, require size upgrades to the radiators and the distribution systems.
When you use a heat pump to replace a hydronic boiler, the same heat pump can also preheat your hot water, then only requiring a small boost of electric heating to bring the water up to shower temperature.
Rather than cooling water for a radiant system in the summer, which will lead to puddles of condensation in your house, for cooling, consider adding a second air-to-air heat pump which can be placed in your attic with small ducts to cool the upper floor, where it is needed the most. This heat pump will also dehumidify your home, which is a large part of the cooling process. As a bonus, this second heat pump can be switched on to ‘heating’ mode for those few really cold days in the winter, providing you with a back-up heat if you need it.
If you choose not to keep your hydronic system, you can opt for a ductless system.
If You Choose A Ductless System…
This is the system you will use if your house doesn’t have ducts and if you choose not to retain your hydronic system with its radiators or radiant floors. This system uses “mini-split” or “multi-split” units mounted on walls or ceilings, similar to wall-mounted air conditioning units that have been used for years. The number of indoor units you need will depend on your home’s size and layout. Sometimes small duct systems are added to allow one indoor unit to serve multiple rooms. These are called “ducted mini-splits.” One outdoor unit can serve one or several indoor units depending on the configuration. One important advantage of this type of system is that you can maintain different temperatures in various parts of your home.
If You Want To Keep Your Gas Furnace As Back-up…
If you have a newer forced-air gas furnace, or you’re not ready to give up a gas furnace, you can pair it with many types of heat pumps in what are called “hybrid” or “dual fuel” systems. These systems use the heat pump until the outside temperature drops below a set temperature or until the heat pump is no longer able to deliver the heat required to meet the temperature you’ve set on your thermostat. At this point, the system switches automatically to the fossil fuel heating system. The homeowner has complete control over the system and can switch to the gas furnace if they’re uncomfortable. There are even some hybrid systems that can be programmed to switch between heating systems based on whether you want to minimize carbon emissions or utility costs.
If You Only Want One Specific Area Heated Or Cooled…
Small air source heat pump units can be mounted into a window opening, much like the air conditioners we’ve used for years. These units are less efficient than central and ducted systems, but they plug into a regular household power outlet and can effectively heat or cool a room.
Still Have Questions?
Of course you do! Here are some of the frequent questions we hear about heat pumps.
This article draws in part from the Canada’s Home Electrification Toolkit. Written by Heather McDiarmid, Building Decarbonization Alliance. Illustrations by Saje Damen. Copyright © 2024 The Building Decarbonization Alliance. This article and the Toolkit have been released under a Creative Commons CC BY-NC-SA license.