This study presents some preliminary results of an on-going European Project, RePublic-ZEB [1], where an analysis is conducted for identifying the cost optimal levels for the existing buildings, towards nearly Zero Energy Buildings (nZEB) performance. The analysis is applied to the reference building for an existing office building in five different countries: Italy, Portugal, Romania, Spain and Greece. The evaluation tool uses a new cost optimization procedure based on a sequential search-optimization technique considering discrete options [2] is applied and the results will be presented in terms of optimal "package of measures", energy consumption and global costs. Finally a cross-country analysis will be performed. © 2015 The Authors.Peer ReviewedPostprint (published version

Reference climatic data have been available since the early 90s in order to ensure uniformity of assessment and repeatability of energy performance calculations: they include monthly means of meteorological elements, as reported in national standards. Other climatic data were provided by ENEA for the period 1995-1999. More recently, new test reference years, representing the basis of UNI 10349 update, were made available by CTI. Some discrepancies between the old and the new sets of data appear. For some reference NZEBs, this paper presents the analysis of the effects of the climatic data on the calculation of energy performance of buildings

The Italian Ministerial Decree 26/06/2015 specifies the requirements of nearly zero-energy buildings (nZEBs) and demands that the energy performance of the new building is compared with that of a reference or target building, which has the same location, function, size, but reference insulation level and technical systems efficiencies. The research aims both to investigate the technical feasibility of design solutions complying with the legislative requirements and to verify the reference building approach. The analysis is applied to a residential building in three Italian climatic zones. The calculations are conducted by means of quasi-steady (UNI/TS 11300) and dynamic (Energy Plus) methods

Building energy performance requirements aiming at the nZEB target have been recently established by the national legislation. In Italy, the requirements are verified through the notional reference building, whose U-values are reduced in two steps: up to 2018 and since 2019 for public buildings, and up to 2020 and since 2021 for all other buildings. This might cause a reduction of the heating need but an increase of the cooling need. The objective of the study is to investigate in which conditions and extent a significant imbalance of the energy needs occurs. Different building types and climatic zones are considered

The study presents some results of the on-going European Project, RePublic_ZEB, on the refurbishment of the public building stock towards nearly Zero Energy Building (nZEB). The work is focused on the application of the nZEB requirements to two existing public buildings representative of the 1960s in Northern Italy. Many packages of energy efficiency measures that comply with nZEB requirements are identified and evaluated. The aim is to promote energy efficient but also cost-effective solutions for the Italian building stock refurbishment. The results are presented in terms of "package of measures", energy consumption, global costs, actualized pay-back period and CO2 emission