Home / That’s how it works – about exhaust air heat

How does exhaust air heating work?

Are you wondering how exhaust air heating actually works? Then we suggest you read this little guide, and you will get the answers. We are quite familiar with heat pumps.

We choose here to describe an exhaust air heat pump. However, the principle is the same regardless of the type of heat pump.

Warm indoor air is drawn from wet areas to the pump. Fresh air is taken in through standard window vents or wall vents. The hot air passes the evaporator. A cooled refrigerant flows through the evaporator. The refrigerant is heated by the warm indoor air and vaporized into gas at the same time as the air is cooled. The cooled indoor air is blown out through the house wall as a residual product.

The gasified refrigerant is led to a compressor where the pressure of the gas is increased. As the pressure increases, the temperature of the gas also rises from about +10 degrees to about 80 degrees.

In this high-pressure area, cold water is led into the condenser. This cold water is heated by the hot gas, which then condenses into liquid. The heated water passes out for house heating and hot water.

When the refrigerant has given up its heat to the water, it passes a valve where pressure and temperature drop sharply. The cold and mainly liquid refrigerant then goes back to the evaporator.

Installerad RX-pump i samarbete med Besqab

When is exhaust air heating suitable?

Basic requirements:

  • The house must have ventilation ducts from all wet rooms plus the kitchen
  • The house must be equipped with windows/wall vents for fresh air intake. Alternatively, air can be taken in through a duct system, so-called supply air.
  • The house should have a water-borne heating system. Radiators or underfloor heating don’t matter.
  • The kitchen fan must go in a separate duct.

An advantage of an exhaust air heat pump is that the indoor air, which is always warm, is used as an energy source. The energy content of this is considerably higher than cold outdoor air. Another advantage is that you get the house’s ventilation in the bargain. The indoor air becomes pleasant and no separate ventilation fan is needed.

Extract air heating in the villa

Fresh outdoor air is brought into the house. The air circulates in the rooms of the house with exhaust air devices. Used room air is vented away through the duct system (the kitchen fan has its own exhaust air outlet). The warm room air is led to the heat pump, which in turn supplies the house with both room heat and hot water. When the room air has passed the heat pump, it is released. The temperature has then been lowered and the heat pump has taken advantage of the energy in the room air.

Comfort cooling in the villa

As the first manufacturer of exhaust air heat pumps, ComfortZone has now developed a new type of heat pump that also provides the house with comfort cooling when needed; ComfortZone Cooling!

In normal operation, the RXC heat pump provides heat to the house, but in Cooling mode the cold is instead taken care of and converted to give the house what we call comfort cooling. In order to produce this comfort cooling, it is required – unlike when heating – that a supply air unit be connected to the heat pump, called T15.

With comfort cooling, the incoming temperature in the rooms can be adjusted to the appropriate level and also, if necessary, cool down the house’s floor loops, all while the heat pump continues to produce hot water for showers and tap water. Simply a “two-in-one solution” in one and the same heat pump!

ComfortZone Cooling is available in versions RXC35 and RXC50 and can be ordered through our retailers.

Why Comfortzone?


ComfortZone has developed a solution with requirements for long life and safe operation. Only through exhaust air
as a heat source, we make it possible to continuously reach an output of 3.5 kW, 5 kW or 6.5 kW.


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