When making an estimate of heat demand, you need to take into account such unobvious details as whether the roof is flat or pitched, or how many panes the windows have. Find out what else to consider when choosing a heat pump.

The ideally selected heat pump should have an output matched to the heating energy demand of the specific building. There is therefore no single universal model suitable for every home. A house may have several dozen square metres of heated floor area, or it may have several hundred. It may be a detached building or part of a terraced development. The type of insulation is also very important, but we will discuss its impact on the choice of heat pump later in the text. For now, let us look at how a heat pump works and why both underestimating and overestimating its output can affect heating efficiency.

How does a heat pump work?

A heat pump uses thermal energy stored in the natural environment for heating. It can draw it from the ground, water or air—these are the heat sources. The energy is collected using a refrigerant, such as difluoromethane, also known as R32. Its temperature is lower than the ambient temperature, even when frost outside reaches -25 degrees. The heated refrigerant becomes a gas, which is compressed by the compressor. Its temperature rises and, through a heat exchanger called a condenser, it heats water that goes to a storage tank and from there to taps or the heating system—for example, radiators or underfloor heating, i.e. the so-called upper heat source.

The refrigerant is reusable; it does not disappear after one cycle. After releasing its heat, the cooled refrigerant reaches the expansion valve. When its state changes back to gas, it can return to the compressor. The cycle begins again.

Choosing a heat pump

Choosing the wrong heat pump may result in the system failing to operate efficiently and the building not being heated as expected. In other words, it will be cold inside. On the other hand, if the building's heating output demand is much lower than the heat pump's output, it will operate uneconomically. That is why it is so important for the estimated heat demand of the home to be as accurate as possible. It is a good idea to commission an energy audit.

Using special calculators or applications, you can also make an initial estimate of the building's heat demand yourself. However, whether we use a professional's help or carry out the analysis ourselves, we should prepare the following information about the building:

  • type of building (e.g. detached house, terraced development, etc.)
  • heated floor area and number of storeys in the heated zone
  • room height
  • thickness and types of materials making up the external walls
  • number and type of windows (e.g. triple-glazed)
  • number of balcony doors
  • whether the building has a basement
  • insulation of the roof or ceiling above the top heated storey (thickness and type), as well as the type of roof (e.g. pitched or flat)
  • ground-floor insulation (thickness and type)
  • underfloor or radiator heating?
  • in the case of existing houses, it is worth knowing the year of construction, as well as the previous annual consumption of the fuel currently used or the amount of gas burned.

The choice of heat pump is also influenced by the desired indoor temperature and the number of people living in the building.

Once all the parameters are known and it is possible to estimate the desired output of the device, you can proceed to choosing its type.

Types of heat pumps

Depending on the lower heat source, heat pumps can be divided into:

  • ground-source, which are additionally divided into heat pumps with vertical or horizontal exchangers,
  • water-source,
  • air-source, among which we can choose monobloc heat pumps (all the pump components are housed in a single casing mounted outside the building) or split heat pumps (the device is divided into outdoor and indoor units connected by refrigerant pipes).

An innovative and interesting solution is a hybrid heat pump. It combines a gas boiler and a heat pump, allowing you to choose which heat source to use at a given time. Hybrid heat pumps can be installed in buildings connected to the gas network. Like other devices, they come in different output ratings, which can be matched to the size of the building. As with air-source heat pumps, there are two types: split and monobloc. Devices of this type work well in renovated buildings. Immergas offers them in its product range.