Life Cycle Cost Optimization of Residential Buildings in Bulgaria: a Case Study of the Building Envelope

Around 60 % of residential buildings in Bulgaria are constructed before the Nineties of the last century, i.e. they have been in use for more than 30 years. Furthermore, the final energy consumption of Bulgarian residential buildings is the highest in Europe. This raises the question of the improvement of the energy performance of existing residential buildings. The current study is intended to assess the influence of the heat transmittance coefficient of the external building envelop elements on the annual energy consumption for heating and cooling and finding its optimal value. Life-cycle cost (LCC) as the optimization criterion is using. The optimization procedure is conducted for the climatic and economic conditions in Bulgaria and taking into account the existing legal framework. The minimum of the building life cycle costs is determined by using a genetic algorithm.