The calculation of the cooling load for the design and/or correct planning of an air conditioning system of any kind or size is based on Regulation VDI 2078. This “Calculation of thermal loads and room temperatures (design of cooling load and annual simulation)” is enacted by the Association of German Engineers (abbreviated to VDI).
Unlike a formal law, a regulation is not binding. However, it includes recommendations and rules and therefore represents the state of the art.
The cooling load, room air temperature and operative room temperatures of all rooms are calculated on the basis of Regulation VDI 2078, regardless of whether they are air conditioned and, if so, how they are air conditioned. All parameters that affect the thermal behaviour of the room in any way are taken into account.
What is the cooling load?
The cooling load consists of the thermal loads to be dissipated from a room to achieve a desired temperature level, and consists of the following:
External cooling load
- transmission heat from adjoining rooms that are not air conditioned, external walls and roof areas
- radiated heat through windows
Internal cooling load
- thermal emissions from people, lighting, machinery and equipment heat
- thermal absorption by material throughput through the room
- heat from chemical reactions
Latent heat loads by moisture
Adding these loads together produces the cooling load of a room that needs to be dissipated by the air conditioning system.
Approximate calculation of the cooling load of single rooms
The disadvantage of the current version of VDI 2078 is that it is similar to a simulation of a building that can only be calculated with the aid of computers, and professional and hence expensive programs. An older version of 2078 provided the option of an approximate calculation, which we have made available in the form of a calculation tool on our website. This does not replace the precise calculation but delivers considerably better values than a calculation using ballpark figures (e.g. 100 w/m²)
We would like to use an example to explain below the general process for using this form.