Energy conservation with Dantherm
heat recovery ventilation units

Get a healthy indoor environment and a sound economy

Energy calculation - what is the net energy saving with a residential ventilation system?
A sound indoor environment is important. So is the global environment. With a heat recovery ventilation unit from Dantherm you will get a solution that saves energy, provides a pleasant indoor environment and contributes to reduced CO2 emissions. Dantherm heat recovery ventilation units are fitted with highly efficient heat exchangers recovering up to 95% of the heat from the exhaust air.

In order to calculate the net saving with a heat recovery ventilation unit, we must take into account the energy consumption for heating and electricity, as the residential ventilation unit uses electricity and at the same time it reduces the heating demand of the house.

Below we have made a calculation where we compare the consumption in a new-build house (constructed in accordance with the latest building regulations) with mechanical heat recovery ventilation, with the consumption in a house with traditional ventilation.  As it appears, there is a nice saving on the total energy consumption.

Energy balance sheet - example

Assuming that:
A tight and insulated detached house of 140 m2 is fitted with a mechanical heat recovery ventilation system with counterflow heat exchanger. The ventilation unit has a heat recovery of 80% and SFP of 1000 J/m3. The house is a standard one-storey detached house with utility room, a kitchen, a bathroom and a toilet.

Annual energy conservation in kWh

Gas consump. heating of ventilated air
Electricity consumption for running of the ventilation system
Cost reduction in kWh


5.720 kWh/year - 482 kWh/year =

5.720 kWh
482 kWh
5.238 kWh

Annual cost reduction in
Energy consump. converted to m3 gas
Cost reduction gas*
Electricity costs** for running of the ventilation system
Cost reduction in DKK
5.720 kWh/year / 11 kWh/m3 =
 9,25 kr./m3 x 520 m3=
2,25 kr./kWh x 520 kWh =

4.810 DKK - 1.170 DKK =
520 m3
4.810 DKK
1.170 DKK

3.640 DKK

Annual CO2

CO2-reduction gas
CO2 extra electricity

0,205 kg/kWh x 5.720 kWh =
0,478 kg/kWh x 520 kWh =
1.173 kg - 249 kg =

1.173 kg
249 kg
924 kg

 * Natural gas price: 9,25 DKK pr. m3        ** Electricity price: 2,25 DKK pr. kWh   

Source: Danish "Videncenter for energibesparelser". 

1 liter fuel = 8-10 kWh. 1 m3 natural gas = 9-11 kWh, (highest for new boilers).

CO2-emissions for various kinds of heating:

  • Natural gas: 0,205 kg CO2 pr. kWh
  • Fuel oil: 0,265 kg CO2 pr. kWh
  • District heating: 0,122 kg CO2 pr. kWh
  • Electricity: 0,478 kg CO2 pr. kWh

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