Cost-optimal renovation and energy performance: Evidence from existing school buildings in the Alps

• We model a quick assessment for the cost-optimal level in case of energy performance standards.
• We investigated the impact of the calculation parameters.
• The results of the cost-optimal energy performance level are between 50 and 60 kW h/m2 p.a.
• The highest impacts on the result arise from the energy variation followed by the energy price and the interest rate.
• The operating time based on the standard of about 12 h per day does not correspond with the reality.

This paper reports a study of cost-optimal building renovation arrangements regarding the heating energy performance. The study is based on 8 different primary schools with different building ages and therefore different constructions. The schools are located in the Alps and thus in a region which is in the antagonism between high energy standards and particular climatic conditions. The calculation method is oriented on standard energy demand and life cycle cost methods. The results show that the cost-optimal performance is between a heating energy demand of 50 to 60 kW h/m2 p.a. Furthermore the building age 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 10–12 cm the windows only reach the highest U-value of 1.2 because of the higher investment costs. Also the heating energy system with their energy efficiency was considered in the study and the change into a more efficient system is proposed in every case.