Method for probabilistic energy calculations : variable parameters

Abstract:
Building regulations in Sweden require that an energy calculation is done for every building to show that the building design meets the maximum specific energy use as outlined in the Swedish Building Code. The result of this energy calculation is always one number, for example a building might use 89 kWh/m2 year when the building regulation requires 90 kWh/m2 year. This level of reporting can lead to conflicts if the measured energy use is over the calculated energy use. With the current tools you need to do a time-consuming parametric study in order to see which risks are associated to the design and material properties.

This paper is part of a project called “Calculation method for probabilistic energy use in buildings” and is developing and testing the application of Monte Carlo simulations using two popular energy calculation tools developed in Sweden. The goals of the project are; to look at which input parameters have the largest influence on the result; to begin defining a realistic spread of the most significant parameters; to study the advantages and disadvantages of probabilistic energy calculations; and to look at the discrepancies between calculated and measured energy use.

This paper presents the results of the first stage of the study defining which input parameters should vary and defining a realistic spread of the values of these parameters. Out of all the input parameters in the case object, it was determined that the method should be tested with 16 parameters with variable values. This paper also presents the preliminary results of an energy calculation done on a real object using the variable parameters and 1000 iterations compared to the base calculation without Monte Carlo simulations.