Determining the Optimal Opening for Multi Skin Facade with External Ventilation



Photo of Peter Simmonds

Peter Simmonds


Building and Systems Analytics



The envelope of the Harbin Bank Building in Beijing has a Multi-Skin Facade where the outer cavity is naturally ventilated. During the design the client raised some critical questions:

  1. What is the optimal size of the openings?
  2. How will outside air move through the outer cavity?
  3. If there is wind against the facade then the top and bottom openings will be equally pressured, so how will air still move through the outer cavity?

These points obviously concerned the client and the solutions had to be explained in plain and simple terms. This paper describes the design of the Multi-Skin Facade and explains with the aid of aero physics how the outer cavity functions under different external temperatures and different wind pressures against the facade. The result of the various investigations was an optimum ventilation opening for the outer skin.


The project brief was straightforward: Provide 40,000 square meters of energy-efficient office space for Harbin Bank’s new headquarters in Beijing. What wasn’t so clear-cut was instruction from the bank’s chairman

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Background – The construction of the façade

As stated before the façade was to be aesthetically pleasing and fully functional, so the choice of glazing was critical. In order to evaluate the performance of the double skin

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The Alternative Façade Constructions

Alternative 1- MSF-1 consisted of the original GL-1 glazing and the original GL-2 glazing which comprised of 8mm YBE 0.138 (2#) + 12 mm Ar (Argon) +6mm clear glass

The Multi

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Aero physics is not a discipline or term with which one is generally familiar in building, although it has played a role in construction for several years now. Aero physics

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From the previous results we knew the climate façade performs well during the summer, the question arises whether the ventilated cavities are required to be closed during the winter months

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The methodology presented in this paper show how understanding the physics of multi skin facades can be used to prove the air movement through the cavity and the openings to

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Special thanks go to Russell Gilchrist of Gensler, who knew exactly what buttons to push in order to obtain the results he wanted.

Rights and Permissions

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Simmonds P. et al. 2012, Tilted Glazing in building simulations and its effect on form refinement of complex facades simbuild 2012 Co-Author

Simmonds P. and Getov P, 2013, AIA Monterrey design Conference Epidermis/Hypothalamus: Building Envelope as a factor controlling occupant thermal comfort Co-Author

Simmonds P., 2013, 12th International Conference on Sustainable Energy Technologies Designing an intelligent building skin for occupant comfort

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Simmonds P., 2016, What are the heating and cooling loads generated from a high-performance facade? Facade Tectonics, 2016

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Tamblyn, R. T. (1993). HVAC system effects for tall buildings. ASHRAE Transactions 99(2), pp. 789~792.

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