Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November.
DESIGN AND VALIDATION OF A FACADE ZIGZAG-SHADING MODEL Johannes Maderspacher1 and Sven Moosberger2 Lucerne University of Applied Sciences and Arts, Department of Architecture & Technology, CH-6048 Horw; Email:
[email protected] 2 EQUA Solutions AG, CH-8934 Knonau; Email:
[email protected] 1
ABSTRACT For a prototype building of a plus energy house, contributed to the Solar Decathlon 2010 by the University of Rosenheim (Rosenheim, 2011), attention was paid to the development of an own solar protection system. This shading device has a very dynamic behaviour for direct solar transmittance (Te) and for the total heat gain coefficient (g). Therefore a special analysis, with a revised double façade model, in the simulation environment was necessary. Satisfying correlation of the simulation results with measurements was met by: • adapting the simple window code in the double façade model with angle dependent Te and g values to consider the complex geometry of the façade • using the “air gap” in the double façade model to account the convective and emitted heat transfer of the preheating shading device.
INTRODUCTION The Solar Decathlon provides the opportunity for students to plan and build a plus energy home. Around 20 universities take part on every Solar Decathlon competition. The project takes about two years and in the end of this time all participating houses have to be built up on a competition area. After one week of contest, in which all homes are compared in detail, a winner will be announced.
The University of Rosenheim took part in the first Solar Decathlon Europe in Madrid. After the student competition the contributed house was built up on the campus of the University. Five week measurements were realized with the aim to compare simulation results of IDA ICE with measuring of a real building.
DESIGN OF EXPERIMENT To focus the validation to the model of the innovative solar protection, four different measurement periods were recorded. This procedure was chosen in order to isolate the different effects and their contribution to simulation uncertainty. During the first two periods, the solar shading system was inactive and the main heat flows were calibrated, including transmission, convection and radiation, as well as heat storage effects by thermal activation of the building components. After this base model calibration, the shading was added to both the real measured building and the simulation model for the third and fourth period. Thus, uncertainties due to an inaccurate base model were eliminated. During period 3 and 4, the façade model therefore causes the main differences between measurement and simulation. This enables a detailed analysis of the developed shading model. The first period – „Free floating without solar protection“: During this period, an analysis of the building “behaviour” in free-floating mode has been realised. The building was exposed to real climate conditions. There was no active climate conditioning. The second period – „Heating without solar protection“: During this period, the air temperature was kept above 21/23 °C with the help of a heating fan, while during periods with high solar radiation, the temperatures could get much higher. The third period – „Heating with solar protection“: During this period, the shading was always closed. As in the second period, the indoor climate was again kept on a minimum temperature of 21/23 °C.
Figure 1: Zigzag-Shading of the prototype building
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Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November.
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The fourth period – „Heating with controlled solar protection“: During this period, the shading was controlled by a pyranometer orientated to south. Again, the indoor air temperature was kept above 21/23 °C.
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Figure 4: Reference angle dependency for glazing transmittance in the simple window model
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