Heat Pumps: Heating and Cooling a Home

A heat pump obtains heat by moving it from air, ground or water rather than burning fuel. It heats in winter and cools in summer, and works best with good insulation and suitable emitters.

An air conditioner takes heat out of a room in summer and dumps it outside. A heat pump applies the same principle in both directions: in winter it takes heat from outdoor air, the ground or water and delivers it indoors. Because nothing is burned, there is no flue, gas boiler or combustion products in the house. For the system to meet expectations, though, it has to be planned together with the building's insulation and heat emitters.

How it works, in plain terms

Inside a heat pump is a closed loop in which a special fluid, the refrigerant, circulates. The fluid absorbs heat from the outdoor source and evaporates, a compressor squeezes it and raises its temperature, and then it releases heat in the indoor heat exchanger and turns back into liquid. The compressor needs electricity, but the system can deliver several times more heat than the electricity it uses.

That ratio is not fixed. The bigger the gap between the source temperature and the temperature needed indoors, the harder the pump works. An air-source pump becomes less efficient in very cold weather, and the same happens when very hot heating water is demanded.

Efficiency figures in manufacturers' catalogues are measured under specific test conditions. In a real house, results depend on the climate, the temperature of the heating system, installation quality and how the system is set up. When comparing units, it is better to look at figures given for different outdoor temperatures rather than a single number, and to ask about noise levels and control options as well. To estimate average efficiency over the season, the designer considers the heat loss of the house together with local climate data.

Types

Air-to-air: heats or cools the indoor air directly. Many split and multi-split air conditioners are in fact heat pumps of this kind. Installation is simple, but they do not make hot water.
Air-to-water: transfers heat from outdoor air to a water-based system such as underfloor heating, radiators, fan coils and domestic hot water. A common choice for private houses.
Ground-to-water: takes heat from pipes laid in the ground or from boreholes. Ground temperature is steadier through the year, so efficiency depends less on winter cold, but it needs excavation or drilling and space.
Water-to-water: used where a nearby water source is available and permitted.

Matching the heat emitters

A heat pump performs best with low-temperature water. That makes underfloor heating its natural partner: a large surface heats the room evenly at a low temperature. Radiators can work too, but they must be sized for low water temperatures. If small radiators chosen for high temperatures remain from an old system, the pump is put under more strain.

Fan coils can be used for both heating and cooling. Cooling through underfloor pipes is also possible, but temperature and humidity need controlling so that condensation does not form on the floor.

Cut heat loss first

A heat pump is sized according to the heat loss of the house. If walls, roof and windows are poorly insulated, a more powerful unit is needed, meaning larger equipment using more energy. The logical order is therefore to improve the building envelope first, then choose the system based on calculated losses.

Picking an oversized unit just to be safe is not a good idea either. A large pump under a small load keeps switching on and off, which reduces both efficiency and equipment life.

Questions to ask while planning

Where will the outdoor unit go? It can create noise near bedroom windows and property boundaries, and it needs free space for airflow.
Where will water from the outdoor unit drain during defrosting in winter?
Is there room in the plant room for a hot water cylinder and the hydraulic module?
Which rooms will have underfloor heating, radiators or fan coils?
If solar panels are planned, how will the pump's daytime consumption be coordinated with them?
Is a backup heat source needed for the coldest days?

In private house designs Zaferoğlu İnşaat fixes the plant room location together with the architectural plan, which makes it easier to reserve space for a heat pump. If you want to plan space and conditions for a heat pump in your new house, contact us.

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