Performance of EN ISO 13790 utilisation factor heat demand calculation method in a cold climate

The applicability of the utilisation factor method EN ISO 13790 is studied in modern Finnish buildings in the cold climate of Finland. The heat-demand results of EN ISO 13790 are compared against a validated dynamic simulation tool. It is shown that, with the default values of the numerical parameters of the utilisation factor, EN ISO 13790 gives in Finnish conditions as much as 46% higher or 59% lower heat demand of the building compared to the simulation tool, depending on the type of the building and its thermal inertia. The results of EN ISO 13790 can be calibrated for the residential buildings with the correct selection of the numerical parameters for Finnish conditions. With the new values of the parameters, the results are in good agreement in most cases; however, the maximum difference between the methods remained 29% for highly insulated residential buildings. For office buildings, heat demand was strongly underestimated in all the cases by the monthly method EN ISO 13790 regardless of the values of the parameters. The results of the study indicate that the monthly method EN ISO 13790 with new determined numerical parameters is reasonably applicable for residential buildings, but not applicable for office buildings. Therefore, the other methods of prEN 13790, i.e., simple hourly or detailed simulation methods, should be used for office buildings.