CEN/TC 89/WG 6 - Calculation of non steady state thermal behaviour of buildings

ISO 13792:2011 specifies the required input data for simplified calculation methods for determining the maximum, average and minimum daily values of the operative temperature of a room in warm periods:
a) to define the characteristics of a room at the design stage in order to avoid overheating in summer;
b) to define whether the installation of a cooling system is necessary or not.

This European Standard specifies a set of assumptions, requirements and validation tests for procedures used for the calculation of the annual energy needs for space heating and cooling of a room in a building where the calculations are done with a time step of one hour or less.
This European Standard does not impose any specific numerical technique for the calculation of the room heating or cooling need and the internal temperatures of a room.
The purpose of this European Standard is to validate calculation methods used to:
   assess the energy performance of each room of a building;
   provide energy data to be used as interface with system performance analysis (heating, cooling, ventilating, lighting, domestic hot water etc).
The validation procedure is used to check the energy need for space heating and cooling based on a transient sensible heat balance model, taking into account:
   the external surface heat balance;
   the conduction through the building envelope;
   the thermal capacities of external and internal structures;
   the internal surface heat balance;
   the air heat balance;
   the heat balance solution method.
All other aspects are given either by prescribed boundary conditions or by input data and are not part of the model validation. It is assumed, that for all these other matters e.g. embedded heating and cooling systems, prescriptive models have to be used according to existing European Standards.
The system performance analysis and moisture balance are not within the scope of this European Standard.

This European Standard sets out the level of input and output data, and prescribes the boundary conditions required for a calculation method of the sensible cooling load of a single room under constant and/or floating temperature taking into account the limit of the peak cooling load of the system. It includes a classification scheme of the calculation method and the criteria to be met by a calculation method in order to comply with this European Standard.
The purpose of this European Standard is to validate calculation methods used to:
   evaluate the maximum cooling load for equipment selection and cooling system design;
   evaluate the temperature profile when the cooling capacity of the system is reduced;
   provide data for evaluation of the optimum possibilities for load reduction;
   allow analysis of partial loads as required for system design, operation and control.
The validation procedure is used to check the room sensible heat balance model, taking into account:
   the external surface heat balance;
   the conduction through the building envelope;
   the effect of the thermal mass of the structures;
   the internal surface heat balance;
   the air heat balance;
   the heat balance solution method.
All other aspects are given either by fixed boundary conditions or by input data and are not in the focus of the model validation. It is assumed that for all these other matters e.g. embedded heating and cooling systems, prescriptive models have to be used according to existing European Standards.
Informative Annex A gives a simplified method for cooling load calculation.

ISO 13792:2005 specifies the required input data for simplified calculation methods for determining the maximum, average and minimum daily values of the operative temperature of a room in the warm period to define the characteristics of a room in order to avoid overheating in summer at the design stage, and to define whether the installation of a cooling system is necessary or not.
The criteria to be met by a calculation method in order to satisfy this standard are also given.

ISO 13791:2004 specifies the assumptions, boundary conditions, equations and validation tests for a calculation procedure, under transient hourly conditions, of the internal temperatures (air and operative) during the warm period, of a single room without any cooling/heating equipment in operation. No specific numerical techniques are imposed by this standard. Validation tests are included. An example of a solution technique is given in Annex A.
ISO 13791:2004 does not contain sufficient information for defining a procedure able to determine the internal conditions of special zones such as attached sun spaces, atria, indirect passive solar components (Trombe walls, solar panels) and zones in which the solar radiation may pass through the room. For such situations different assumptions and more detailed solution models are needed.