Experimental Evaluation of Airflow in Naturally Ventilated Active Envelopes

Abstract

Active envelopes are characterised by two glazed surfaces separated by a ventilated cavity in which a shading device is placed. Thermal performance of active envelopes is governed by the airflow through the cavity. Until now, there is a lack of knowledge about the amplitude and direction of the airflow in naturally ventilated active envelopes. In this paper we report on the airflow in the naturally ventilated active envelope at the Vliet building of the Laboratory of Building Physics in Leuven, Belgium. (1) The airflow was experimentally determined by measuring the pressure difference over a ventilation grid. This method shows several advantages over traditional methods. (2) Thermal buoyancy and wind pressure differences govern the airflow. For both phenomena, measured data were compared with models. It was found that at low windspeeds and upward flow conditions, a linear relation between the pressure and temperature difference could be obtained. For higher windspeeds simple models cannot accurately predict the complexity of the airflow in naturally ventilated active envelopes due to the location of the measurement probes and due to wind washing effects imposed by altering wind directions.

Keywords

active envelope double skin facade airflow tracergas natural ventilation thermal buoyancy wind pressure difference

Get full access to this article

View all access options for this article.

References

Ashrae , 1997, ASHRAE Handbook of Fundamentals, Atlanta.

Andersen, K.T. , 1995, “Theoretical considerations on natural ventilation by thermal buoyancy,” Ashrae Transactions, 101(2): 1103–1117.

Baker P. , Saelens D. , Grace M. and Inoue T. , 2000, Advanced Envelopes. Methodology, Evaluation and Design Tools, Final report IEA Annex 32 (IBEPA), Leuven, Acco.

Baskaran B.A. and BrownW.C. , 1992, “Performance of Pressure Equalized RainscreenWalls under Cyclic Loading,” Journal of Thermal Insulation and Building Envelopes, 16:183–193.

Bejan A. , 1993, Heat Transfer, New York, Wiley.

Blocken, B. and Carmeliet J. , 2000, “Spatial and temporal distribution of driving rain on buildings,” Submitted to Wind and Structures.

Busselen B., Mattelaer P., 2000, Experimentele evaluatie van actieve gevels systemen(Experimental evaluation of active envelopes, in Dutch), MS thesis, KU Leuven.

Compagno A. , 1995, Intelligent Glass Façades—Material, Practice, Design, Basel, Verlag für Architektur.

Daniels, K. , 1997, “Doppelfassade—Ein mu• für Hochhaüser?” (Double skin envelopes—Imperative for high rise buildings?, in German), Detail, 3:349–354.

10.

Faist A.P. (red.), 1998, La façade double peau. Mesures in-situ et en laboratoires(Double skin facades. In situ and laboratory measurements, in French), research project Ecole Polytechnique Fédérale de Lausanne, Institut de Technique du Batiment.

11.

Gertis, K. , 1999, “Sind neuere Fassadenentwickelungen bauphysikalisch sinnvoll? Teil 2: Glas-Doppelfassaden (GDF)” (Are new envelope technologies useful from a building physics point of view? Part 2: Double skin facades, in German), Bauphysik, 21:54–66.

12.

Jones J. , Messadi T. and Li S.-S. , 2000, “Experimental Study of the Cooling Season Performance of Ventilated Double-Glass Envelope Cavities,” in: Proceedings of the International Building Physics Conference Eindhoven September 18–21, 2000, pp. 357–365.

13.

Li Y. , 2000, “Buoyancy-driven natural ventilation in a thermally stratified one-zone building,” Building and Environment, 35:207–214.

14.

Li Y. and Delsante A. , 2001, “Natural ventilation induced by combined wind and thermal forces,” Building and Environment, 36:59–71.

15.

Onur N. , Sivrioglu M. , Turgut O. , 1996, “An experimental study on air window collector having a vertical blind for active solar heating,” Solar Energy, 57(5):375–380.

16.

Park S.D. , Suh H. S. and Cho S. H. , 1989, “The analysis of thermal performance in an airflow window system model,” Proc. of the ASHRAE/DOE/BTECC/CIBSE Conference, Thermal Performance of the exterior Envelopes of Buildings IV, pp. 361–375.

17.

Raatschen W. , 1995, “Tracergasmessungen in der Gebaüdetechnik, Luftaustauch—Messung und Simulation” (Tracergas measurements in building engineering, air change—measurement and simulation, in German), gi—Gesundheitsingenieur, 116(2) 78–87 and 116(3): 129–138.

18.

Rodrigues A.M. , Canha da Piedade A. , Lahellec A. , Grandpeix, J.Y , 2000, “Modelling natural convection in a heated vertical channel for room ventilation,” Building and Environment, 35:455–469.

19.

Sedlaeck G. and Ziller C. , 1997, “Stömungstechnische Untersuchungen von Doppelfassaden,” (Research on airflow in double skin facades, in German) Proceedings of Symposium DGF-Au enwandenprogramm, Berlin, IRB-verlag, pp. 127–136.

20.

Stoll, Joachim , 1997, “Doppelschalige Fassaden in Hochhäusern” (Double envelopes in high rise buildings, in German), in: Doppelfassaden und Technische Gebäudeausrüstung(Double envelopes and building installations, in German), Fachinstitut Gebäude-Klima e.V., pp. 95–124.

21.

Suresh Kumar K., 1998, “Pressure Equalized Rainscreen Approach toWall Design: Past Accomplishments and Future Challenges,” Eindhoven, Technical Report FAGO 98.25.K TUE.

22.

Zhang J.S. , Janni K.A. , Jacobson L.D. , “Modelling natural ventilation induced by combined thermal buoyancy and wind,” in: Transactions of the ASAE, 1989, Vol. 32(b), pp. 2165–2174.

23.

Ziller C. et al., “Naturliche Belüftung eines Hochhauses mit Doppelfassade” (Natural ventilation in high rise buildings by means of a double skin envelope, in German), in: KI 32, 1996, pp. 343–346.

24.

Ziller C., 1999, Modellversuche und Berechnungen zur Optimierung der natürlichen Lüftung durch Doppelfassaden(Experiments and models to optimize natural ventilation in double skin facades, in German), Ph.D. thesis, Shaker Verlag, Aachen, 96 p.)