Cost-optimal design for nearly zero energy office buildings located in warm climates

The improvement of energy efficiency and the integration of renewable energy in buildings are key elements of current European policies. According to the recast of the Directive EPBD (Energy Performance of Buildings), Member States have to target nZEBs (nearly zero energy buildings) and minimum energy performance requirements within a cost-optimal framework by 2020. This study reports the comparative methodology reported in the EPBD, aimed at the establishment of cost-optimality in office buildings located in a warm climate. A number of energy efficiency measures have been selected and applied to the envelope and the systems of a virtual reference office building. Technical features and energy performance calculations have been assessed for the obtained configurations. Primary energy consumption and global costs have been derived to identify the cost-optimal configuration from a financial and macroeconomic analysis. The paper shows the suitability of the methodology to support the design of cost-effective energy efficient solutions in new office buildings. Results show technical variants selection able to a decrease primary energy consumption by 39% and CO2 emissions by 41% at the lowest cost. They also illustrate how to design cost-optimal nZEBs for a warm climate in compliance with EU (European Union) policies. •Energy performance and global cost evaluation have been performed for building in the southern Italy.•Energy efficiency measures have been applied to the envelope and the system for reference office building.•The comparative methodological framework is applied to obtain cost-optimal levels for new building.•Analysis of office buildings by a comparative methodological framework.•Achieving the nZEB target seems to be feasible in many cases.