At the design stage, it is desirable to be able to predict the indoor thermal climate that will result from a given combination of building construction, heating system, and outdoor climate. Several large computer programs can be used to predict heating and cooling loads, indoor air temperatures, surface temperatures, and humidity, but these programs are often difficult and expensive and are used mainly for large buildings.

This paper presents a simplified calculative method to evaluate the thermal indoor environment at the design stage. The method is proposed in the new Nordic Guidelines for building regulations. The parameters of this method are operative temperature, floor surface temperature, and radiant temperature asymmetry, which are calculated and then compared with existing limits for an acceptable thermal environment. The procedure, which can be performed easily by hand calculations, is demonstrated by examples.

The paper also presents the requirements for an acceptable thermal environment, which are specified in the new Nordic Guidelines.