Calculation of Cost Optimal Levels of Minimun Energy Performance Requirements for Retrofit Measures on an Examplar Office Building

The European Directive about “Energy Performance of Buildings” of 2010 (EPBD recast, 2010/31/EU) introduced the concept of cost optimal level of minimum building energy performance: energy analyses have to be coupled with economical assessments when a building is investigated. The design both of new buildings and of retrofitted existing buildings should be developed taking into account the results of the “cost optimal” analysis. In this paper, an existing office building is studied: it is an exemplar Turkish office and it needs a renovation to reduce its energy consumption. Two different locations are considered: Ankara as a representative city of tempered dry climate and Antalya as a representative city of hot-humid climate of Turkey. After the illustration of the characteristics of the exemplar office and the definition of its total energy demand, a number of possible retrofit actions are listed and some specific packages of retrofit measures are selected and applied. The measures are addressed to the building envelope, to the heating/cooling systems and to the lighting system. Potential energy savings are evaluated and the cost optimal analysis is carried out for each of the selected package. Cost optimal levels, calculated with different period for the cost analysis, are highlighted and the results are critically discussed. Results mainly show the high influence of the imposed boundary conditions for the calculations: the assumptions have significant impact both for the energy and the cost calculation. As a consequence, the definition of a common approach is fundamental to avoid unrealistic and incomparable results.