Double-Skin Facade: Modelling and Experimental Investigations of Thermal Performance

Double-Skin Facades (DSF) are gaining popularity that, in fact, appears to be independent from sturdy critics of the concept in the past years. DSF buildings are being built in Europe and worldwide, DSF concept is being taught at schools of architecture and fully glazed office buildings are being favored by companies and their employees.

To bring the reduction of energy use in these buildings application of suitable tools and methods is necessary to achieve successful design solutions.

Earlier work on the topic of DSF modelling was examined from various publications. As a result, the main difficulties experienced by scientists when attempting to model DSF thermal and energy performance were examined. In addition, the lack of experimental studies and empirical validation of models was realized, many numerical models have not been empirically validated and most of them require an expert knowledge to perform the simulations.

To fill in the gap of lacking experimental data a range of measurements was carried out in an outdoor, double-skin façade full-scale test facility ‘The Cube'. As a result, three complete sets of experimental data were composed. These are available for external air curtain, transparent insulation and preheating operation modes of DSF cavity. The data sets include measurements of naturally induced air flow, temperature gradients, velocity profiles, climate data, etc.

Two data sets were used for further empirical validation of building simulation software for DSF modelling within IEA Annex 34/43, subtask E "Double-Skin Facade". The results of empirical validation are discussed in this work.

Discussion and analysis of experimental results is carried out. It has lead to hypothesis of recirculation flow phenomenon in the DSF cavity. Finally, a suggestion of a new numerical model is developed to account for recirculation flow appearance in the DSF cavity. The model is based on a simple mass balance between the boundary layer flow and the main flow in the cavity.