Where does the difference between the building's heat load and the total declared room loss come from?

Product	InstalSystem 5
Type of article	TIP&TRICK
Source for translation	2024-12-11

Problem description

The design heat load calculated in accordance with EN 12831 may differ from the sum of losses of individual rooms. This results from the calculation methods given in EN 12831. The difference in results may be significantly influenced by:

• The fact that when calculating the design thermal load of a building, half of the infiltration losses are taken into account, and the thermal load of the room takes into account 100% of this air.
• Losses to rooms belonging to other Building unit/Appartment. In these cases, temperatures on the other side are taken into account in accordance with the "Temperature of adjacent heated spaces" table. For this reason, there will be transmission losses to rooms belonging to other Building unit/Appartment, even when the design internal temperature of the adjacent room is the same as the calculated room. In the calculations for the building, these losses are not taken into account.

It is possible to check the impact of these losses by following these steps:

• in the Thermal calculations of building options, in the Determine temperature of adjacent space list, select the Always adopt design temperature of adjacent space option (this can be selected both for the entire building and for each building unit separately),
  

  

  1. Always adopt design temperature of adjacent space

  
  
  

  

  2. Temperatures of adjacent spaces equal to design

  
  
• performing calculations for the Thermal calculations of building module.