Reduction of space heating energy through minimisation of life cycle cost 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 house is heated by a direct electric heating system. 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 of ventilation air) which are defined within set limits.

The assumptions for the LCC data are: number of years under study (20 and 50 years), escalation of electric energy price (1 and 5%) and real interest rate (2.94 and 4.90%). The general solution for the LCC minimisation goes towards reducing the energy cost for space heating by investing in the insulation of the house and using better windows. It suggests lowering the U- values for the external wall, roof, floor and the window from their initial
values to be equal to, and sometimes lower than, those for the so-called “Low Energy House”. The optimisation results indicate that 28 to 49% reduction in space heating is achieved compared with the reference case (Standard House 2003).