LAUSR

Abstract The present study includes a combined assessment of the energy efficiency and economic performance of energy measures in five-story existing and newly constructed office buildings in Greece. The building primary energy consumption and investment and operation & maintenance costs are calculated per Directive 2010/31/EU and EN 15459-1 standard. VRV heat pumps are the most cost-effective heating/cooling system while also being associated with the lowest primary energy consumption (PEC) levels. Meanwhile, LED lighting systems with lighting controls are indispensable for achieving cost-optimality in all investigated scenarios and obtain nZEB status in newly constructed buildings, while also resulting in substantial PEC reduction in older buildings, with the contribution of automation systems being very important as well. The defined nZEB targets can be reached with building envelope materials of various U-values if accompanied by sufficient efficiency measures; on the contrary, extremely low U-value components (especially windows) do not appear to be particularly cost-effective. The installation of PVs is crucial for reaching the nZEB threshold, especially in new buildings, being also advantageous from an economic viewpoint. Notably, none of the considered interventions results in NZEB PEC according to the assumed NZEB threshold values which are arbitrarily defined in the study based on the reference building PEC and that are possibly overambitious.