Ground source heat pumps
Ground source heat pumps (GSHP) release heat into and absorb heat from the ground. They require underground piping: in horizontal trenches below the frost line or in deep, vertically bored holes. They can meet a home’s heating and cooling needs through the entire year and can also be used to help with water heating.
GSHPs are particularly efficient heat pump systems because the ground experiences only small seasonal shifts in temperature, but they are also expensive to install due to the underground piping. GSHPs are not always feasible in urban settings and are more commonly used in rural areas.
Air source heat pumps
Air source heat pumps release heat into and absorb heat from the outside air. They have an outside unit that looks similar to that of a central air conditioner and an inside coil that may be connected to the ductwork or water-based heating systems (eg radiators). In the Waterloo Region climate, a backup heating source may be required depending on the model and may be built into the system. The different types of air source heat pumps are described below.
Cold climate air source heat pumps
Cold climate air source heat pumps (ccASHP) make use of more recent improvement in heat pump technology allowing effective, reliable, and efficient year round climate control even in colder climates, such as Waterloo Region. The efficiency drops on very cold days: some makes and models may require an electric resistance heater as backup in our climate.
The key is the variable-speed compressor and air handler, which allow the heat pump to have greater capacity and efficiency at colder temperatures, without it being oversized for milder temperatures or when used for air conditioning. An electric resistance heater is generally used as the backup heating system for very cold conditions and when the outside coils are in defrost mode, allowing these systems to operate without fossil fuels. A ccASHP can reduce a Waterloo Region home’s greenhouse gas emissions by 40-70% depending on the original fuel, electricity sources, and other home energy uses.
Dual fuel heat pumps
Dual fuel air source heat pumps (DFHP) can provide all of the summer cooling needs and they can efficiently provide heat for a home until outside temperatures fall below the operational temperature range (often the low end of the range is somewhere between -5’C and +5’C). These systems comprise a heat pump paired with a conventional heating system, usually a furnace that provides heat when temperatures are below the heat pump’s operating range.
DFHPs can be programmed to either switch between heating sources to maximize financial savings or to maximize greenhouse gas emissions reductions. The total emissions reductions are hard to estimate as they are dependent on how the DFHPs are programmed and the outdoor temperatures. Very rough calculations for a typical home in Waterloo Region suggest that up to 50% of a home’s heating needs could be met with a good quality DFHP, although their overall energy efficiency may be lower than cold climate ASHPs. This translates to a greenhouse gas emissions reduction for a typical Waterloo Region home of up to 20-35% (50% of the impact of a ccASHP).
Mini/multi-split heat pumps
Mini-split or multi-split heat pumps (MSHP) use small wall or ceiling mounted heating/cooling units that provide heating and cooling to a single room or section of a home.
Some newer units are rated for cold climates and may be able to operate efficiently even at very low temperatures. Many units, however, require a backup heating system, such as electric baseboard heaters, for colder days and nights. These are usually ductless, releasing conditioned air from the indoor unit directly into the room. MSHPs may have one (mini-split) or many (multi-split) indoor mounted units connected to one outside unit. Multi-split systems allow for zoned temperature control throughout the house. These heat pumps are good solutions when zoned heating is required, when there is no existing ductwork, or when extra heating is required for an addition.
Air-to-Water Heat Pumps
Heat pumps can even work with water-based heating systems (hydronic) such as radiators and in-floor heaters or fan coils: these are called air to water heat pumps. They use the same outside unit as a conventional ASHP but the inside unit transfers the heat to or from the water that is circulated in the radiators or in-floor systems.
These may also provide domestic hot water. When the system requires a backup heat source, either an electric resistance heater or a conventional system that uses fossil fuels can be used.