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Saving heating costs by means of a specific example

The Energy Performance Certificate makes it possible. Since the last German Energy Savings Regulation came into force, it has become possible and even obligatory to assess existing flats in terms of energy, too. In the this way, flats have become comparable just like the fuel consumption of different motor vehicles is compared day by day and low consumption levels are regarded as a quality feature.

Flats with high energy efficiency and low heating costs are more attractive and easier to rent than flats which have not been refurbished. The actual heating costs saved by installing a room ventilation system depend on numerous influencing factors, primarily on the behaviour of the owner or tenant. However, approximate values are possible, as illustrated by the calculation example: Flat of 90 m², room height: 2.50 m, heated room volume Ve = 225 m³


Heating costs savings : Heizkosten/Jahr = heating costs/year; Fensterlüftung = ventilation by opening windows


According to the German Energy Savings Regulation (EnEV)

the ventilation heat loss

is calculated

as follows:


Qv = 66 x Hv

where Hv = 0.19 x Ve

Qv = 66 x 0.19 x 225 m³ = 2822 kWh


The EnEV is based on "standardised" people with standardised ventilation behaviour and therefore on an air exchange rate of 0.7 h-1.


Ventilation heat losses in real life:

In practice, the air exchange rate may absolutely be at 2.0 h-1 due to incorrect user behaviour (leaving windows ajar), in which case the actual ventilation heat losses are, for example, 8,000 kWh per year (corresponding to costs of, for example, 800 € per year, depending on the current energy price and energy price increase rate).

Our calculation example is based on the assumption that up to 70% of the ventilation heat requirement can be saved with a Pluggit ventilation system. This already takes into account temporary opening of windows and doors.

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