In search of the cost optimised energy-saving renovation - evaluation of typical residential buildings in Austria

This paper represents a study of cost-optimal building renovation arrangements regarding the heating energy performance. The study is based on typically residential buildings with different building ages and therefore different constructions. The calculation method is compiled on standard energy demand and the net present value method. The results show that the cost-optimal performance is between a heating energy demand of 30 to 40 kWh/m(2) GFA p. a. The building age with the different construction qualities has a high effect on the results of the net present value. Also the investment costs of the different building renovation arrangements show a high effect on the results concerning the cost optimal renovation measurements. Where the insulation thicknesses of the envelope have proposed thicknesses of about 14-18 cm the windows only reach the highest U-Value of 1.2 because of the higher investment costs. Furthermore the sensitivity analysis shows the high impact of the necessary input calculation parameters, like the energy price, the interest rate and the energy price variation. The study considers several ways which can improve the decisions about the renovation possibilities. These include not only the decision of the renovation but also the necessary arrangements, which could be integrated in the procurement.