Optimizing the insulation thickness of walls of existing buildings with CHP-based district heating systems

Abstract

The heat demand of existing buildings can be reduced by improving the thermal properties of building envelope. Moreover, the heat medium temperature of district heating (DH) systems may also be influenced by adding insulation materials. An optimization model used to determine the optimum economic insulation thickness of walls (OEITW) of existing buildings with combined heat and power (CHP)-based DH systems was established based on energy grade and amount of energy. An existing residential building in Beijing, China, was used as the basis of the case study. The impact of insulation thickness (IT) on energy grade and amount of energy was studied. Sensitivity analysis method was used to investigate the impact of electricity price, interest rate, insulation material price and absorption heat pump price on the OEITW and minimum annual total cost (MATC). Results show that the OEITW and MATC can be obtained by using the optimization model. The heat demand and heat medium temperature can be lowered through adding insulation materials, resulting in the reduction of energy grade and amount of energy. Sensitivity analysis results show that the impact of sensitivity factors on the OEITW and MATC are different.