Hourly dynamic and monthly semi-stationary calculation methods applied to nZEBs: Impacts on energy and comfort

The EU Directive 2010/31 abstained from prescribing harmonized and strict requirements for nearly Zero Energy Buildings (nZEBs), to provide EU countries flexibility and room for maneuver in setting national targets, in view of the impact of local climatic conditions and specific territorial and socio-economical features on heating and cooling needs. Benchmarks are usually provided in terms of primary energy needs, however the definition of accurate calculation methodologies, notably as regards the cooling share, is a rather challenging task. Nonetheless, its accomplishment is cardinal to countries, like Mediterranean ones, were the building performance is mostly dictated by summertime sensitivities. This paper presents a cutting-edge approach to nZEB performance analysis: the monthly quasi steady-state (EN 13790 as implemented in Italian UNI/TS 11300) and hourly dynamic calculation methods (developed under the standard UNI EN ISO 52016-1:2018) are compared, with due attention to the cooling energy consumption, to spot pros and cons of a finer temporal discretization. Potential nZEB design alternatives in three different Italian climatic zones are contemplated and used to confront the effectiveness of the above procedures. (paper)