Minimisation of life cycle cost of a detached house using combined simulation and optimisation

In the current study, minimisation of life cycle cost (LCC) for a single family detached house is achieved by combined simulation and optimisation. The house has a typical Finnish construction with initial U-values in accordance with the Finnish National Building Code C3 of 2003. The implemented approach is coupling the IDA ICE 3.0 building performance simulation program with the GenOpt 2.0 generic optimisation program to find optimised values of five selected design variables in the building construction and HVAC system. These variables are three continuous variables (insulation thickness of the external wall, roof and floor) and two discrete variables (U-value of the windows and type of heat recovery). This investigation shows the advantages gained from the implemented approach of combining simulation and optimisation. The solution suggests lowering the U- values for the external wall, roof, floor and the window from their initial values. The exact values of the optimised design variables depend on the set up of the LCC data for each case. Reduction of 23-49% in the space heating energy for the optimised house is obtained compared with the reference case. Verification of the GenOpt results is made by comparison with results from a brute-force search method, which indicates that GenOpt has found, or has come very close to, the global minimum in the current study.