Simulation of thermal indoor climate in buildings by using human Projected Area Factors

Nowadays many new and old buildings in Denmark have large glass surfaces. This is a consequence of the technical development of windows with low U-values that has made it possible to build houses with windows from floor to ceiling in northern climates. On the other hand if one is sitting close to these large windows on a cold winter day it is recognized that this can cause thermal discomfort.

The calculation of this discomfort needs to be taken properly into account in the simulation of the thermal indoor climate and energy consumption of the rooms. The operative temperature can be used as a simple measure for thermal environ-ment. The operative temperature is a function of the air temperature, the mean radiant temperature and the relative air velocity.

However, in many programs for calculation of energy consumption and thermal indoor climate the model for calculating the mean radiant temperature has traditionally been based on the calculation of an area weighted mean value independently of the location in the room. In practice the location of the per-son in the room has a significant influence and inhomogeneous radiation plays an important role for the us-ability and functionality of the room.

In order to calculate the mean radiant temperature as function of the per-son´s location in the room one needs to calculate the angular factor between the person and the surfaces. This paper describes a method for detailed calculation of the operative temperature and how it can be implemented in programs for dynamic building thermal analysis.

The method is demonstrated in a newer apartment with windows from floor to ceiling and shows how impotent it is to include the radiant effect from the glass sur-faces and how it influences the indoor thermal climate significantly.