The EN ISO 52016-1:2018 technical standard has introduced a new simplified dynamic method for the calculation of the building energy need for heating and cooling. This new procedure combines a low amount of input data required, as for the previous quasi-steady and dynamic simplified methods of the withdrawn EN ISO 13790 standard, with an increased accuracy, which would reduce the gap with detailed dynamic methods. This work is part of a broader research activity aimed at investigating the new simplified dynamic model and highlighting its strengths and weaknesses, in terms of accuracy and robustness. Specifically, the work addresses the parameters that have a great influence on the final results and the effects of uncertainties in input data. To this purpose both standard and tailored energy performance assessments have been applied, in particular in the first one a continuous operation period of the space heating system was supposed, and in the second one an intermittent operation system was chosen. A sensitivity analysis was also carried out to quantify the variation of the heating and cooling loads with the set-point temperature, the windows physical properties, the heat capacity and the thermal transmission properties of opaque components, as well as the occupancy related input parameters, such as the internal heat gains and the ventilation flow rate. The analysis was applied to a multi-unit residential building located in Rome and built in the first half of the 20th century. The results outline absolute relevance of the set point temperatures. The significance of occupant behaviour and the importance of the correct definition of the component thermal properties is also pointed out through the comparison between the standard and tailored assessments.
The recently issued EN ISO 52016-1 technical standard provides a new simplified dynamic method for the building energy performance assessment. Since an extensive validation of the EN ISO 52016-1 hourly method is still missing, the present work investigates the effect of the main modelling assumptions—related to the heat balance on the outdoor and the indoor envelope surfaces—on the building thermal behaviour. The model validation was carried out by assessing the accuracy variation consequent to the application of the EN ISO 52016-1 modelling assumptions to a detailed dynamic calculation tool (EnergyPlus). To guarantee a general validity of the outcomes, two buildings, two levels of thermal insulation, and two Italian climatic zones were considered, for a total of eight case studies. To explore different applications of the standard method, the analysis was performed both under a free-floating condition—to evaluate the accuracy of the model in predicting the indoor operative temperatures—and to assess the annual energy needs for space heating and cooling. Results show that the assumptions related to the definition of the external convective and the shortwave (solar) radiation heat transfer lead to non-negligible inaccuracies in the EN ISO 52016-1 hourly model.
In the last years, new technical standards for the assessment of the energy efficiency of technical building systems were developed by the European Committee for Standardization (CEN). These procedures were conceived as to combine the easiness of the calculation methodologies and their related assumptions with a sufficient level of accuracy. While the former objective is often achieved, the latter is a challenging task as the procedures sometimes fail to simulate in a proper way the actual performance of the technical systems. On the other hand, the detailed procedures applied by detailed dynamic energy simulation tools are more precise and complex; however, for their application, they need a wide range of input data that are often hard to collect. For this reason, simplified procedures are now commonly applied, above all in the case of existing buildings. Nevertheless, these procedures need to be deeply analysed and validated. In this paper, the main standard calculation procedures addressed to chillers and specified in EN 16798-13:2017 were analysed, with a focus on the required input data and the calculation procedures. The same approach was then applied to the more detailed calculation methods used in the dynamic tools EnergyPlus and TRNSYS, and the results were compared. The theoretical analysis was then followed by a case study approach. A reference office building, representative of the Italian building stock, was selected and analysed in two different Italian climatic zones. The determination of the thermal energy need for cooling was performed by means of EnergyPlus, while the assessment of the energy demand related to technical building systems was performed both with EnergyPlus and with the standard procedures. This paper is part of a wider research activity finalised to the analysis of the technical building systems calculation procedures, taking into account different generation systems and thermal coupling modes between the technical systems and the building itself.
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