Modelling of double ventilated façades according to the CEN Standard 13790 method and detailed simulation

The European Energy Performance of Buildings Directive(EPBD) encourages the use of technologies in buildings that can potentially improve their energy performance.Double ventilated faades can often have a positive contribution to this objective and their effect has to be quantified during the calculation of the overallenergy performance of the buildings. The updated EN ISO 13790 Standard is part of the new set of CEN Standards that have to be delivered to support the EPBD requirement for a general framework for the methodologyof calculation of the total energy performance of buildings. It contains a method to calculate the contributionof the double ventilated faades to the annual heatingand cooling requirements of buildings. At the same time (validated) detailed simulation tools, which are also allowed in this Standard, offer an alternative way to quantify the effect of the double ventilated faades on the buildings energy performance. This paper examinesa case study where the ESP-r simulation program and the method described in the Standard were used for a common building specification to investigate the impacts from a double ventilated faade on the energy performance of the building. It discusses the potential differences that might appear when a detailed simulationtool (ESP-r) is used with constrained (according to the Standard) inputs and also unconstrained inputs, compared to the outputs obtained from the method describedin the Standard. Some parametric studies are included to show whether the same trends are obtained using both the method in the Standard and the detailed simulation approach.