An optimal maintenance plan for building envelope insulation materials after retrofitting

Energy conservation in the building sector is drawing increased attention in the world. It is found that around 40% of the European Union's overall energy consumption is used by buildings. Among the energy used by different systems and components in a general building, its envelope makes a great contribution. As a result, properly designed retrofitting and maintenance plans for building envelopes can make a big difference in terms of energy usage of buildings. In this paper, a multi-objective optimization model for determining an optimal maintenance plan of building envelope components after retrofitting is presented. Specifically, windows, external wall insulation material and roof insulation material are the components considered for retrofitting and maintenance. After the items are retrofitted with their better counterparts, an optimal maintenance plan is developed for the purpose of energy consumption minimization with economic performance taken into account. Net present value, payback period and life-cycle cost, which are important factors for decision makers are taking into consideration when formulating the minimum energy usage maintenance plan. Eventually, an optimization model is formulated with two objectives, one to maximize energy savings and the other to maximize economic benefits during the model's evaluation period. A case study on a 70 years old family house is conducted as an illustrative example. The results show that around 40% of the energy consumption of the building can be avoided by applying the retrofitting and maintenance plan.