Heating load calculation

Calculation of the room heating load

By calculating the heating load, your heat generator is adjusted to the size actually required. You will not lose money by oversizing your new heating system. Save twice! The need-based design of a heating system not only reduces the investment costs considerably, but also the running costs in the future are significantly reduced.

We would be pleased to advise you on the subject of heating load calculation and check whether a calculation is useful in your case. During the elaboration we consider your defaults and desires all the more to ensure a dimensioning of your new heating system according to your needs. As the cake chart shows, the calculation also reveals which components lose most heat. Thus, this representation is a good basis for further optimizations of the building envelope.

From which building size should a heating load calculation be carried out? Installations in existing buildings are in most cases oversized. In the past, the heat output and the design of the pipelines were calculated generously, as fuel costs were lower and the emission of emissions had not yet been checked with today's care.

Today, the plants are designed according to requirements.

Heating load calculation yes...but not in detail:
For family houses, which are supplied with a condensing boiler (gas or oil), an exact calculation is often not necessary for the following reasons

The output of the available condensing boiler (gas or oil) is often higher than the actually required output (with many manufacturers the smallest unit version is already over 10 kW).
The units are operated modulating (gas) or stepwise (oil). This means that the units can always adapt the output to the current requirements. If a unit is designed too large, it can still be operated as required due to this characteristic.
The additional price for a unit with a larger output (e.g. comparison of 15 kW to 25 kW) is usually so low that a detailed calculation shows hardly any potential for saving investment costs.
If the hot water preparation is realised via the central heating system, the system must provide a certain minimum output, which in small buildings is often higher than the required output for heat supply.
Heating load calculation...in any case detailed:
When using regenerative systems (heat pumps, wood pellet systems, solar systems) a detailed calculation is always useful

Systems for the use of renewable energies rarely have a large modulation range. A precise design is necessary for a demand-oriented mode of operation. In addition, damage to the system can be caused by incorrect design.
For example: If the bore hole of a heat pump system for the use of geothermal energy is designed too small, the expensive heat source (borehole or ground collector) can be damaged by overloading the heat source.

In the field of systems for the use of renewable energies, the investment costs can be considerably reduced by a design that is tailored to the requirements.
For example: If a heat pump with a ground heat source (borehole) is too large, additional costs are incurred in various places.

larger heat pump (possibly additional costs for larger buffer storage tank)
more drilling meters (additional costs are about 1000 €/kW)

For the area of apartment buildings and commercially used units

From a certain building size upwards, a heating load calculation is always useful.

The greater the demand, the higher the savings potential. For systems with a higher output, other factors also play a role, which can have a considerable impact on the investment costs:

  • Can a wall-mounted unit be used, or must the floor-standing variant be used
  • Pump groups and distributors are designed according to the required capacity
  • The diameter of the exhaust pipe must be larger
  • The gas pipe must be laid in a larger nominal width

Alexander Lückge B.Eng.
Business Unit Manager, Department Private Customers