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Research focus
The use of double facades to facilitate demand controlled ventilation

Researcher: Zhihong Liao
Funded: DTI Technology programme/industry 
Value: £68,300
Lead partner: CWCT 
Partners: Allies and Morrison 
Bennetts Associates 
Carillion plc 
Council for Aluminium in Building 
Faber Maunsell Ltd 
Hoare Lea 
Sir Robert McAlpine Ltd 
Status: Begins January 2007


The objective of this work is to establish virtual precedents for the use of double facades that provide a pressure-moderated plenum from which air can be drawn for demand controlled ventilation. The performance of such a facade requires knowledge of how to determine the best geometry, how to position and size the vents in the outer and innter skins, and how to determine how effectively it may be used.

This project will:

  • Undertake a desk study of the wind events in the UK, particularly the periods of low or no wind. This will comprise statistics showing the performance required of the facade if it is to be effecitve for a given percentage of the time.
  • Facade geometries will be postulated for a number of building layouts to optimise the use of theremal stack effect and also the transfer of air from one to another.
  • The performance of the double facade as a pressure-moderated plenum will be modelled using CFD software to show how large facades may be before pressure variations in the plenum interfere with ventilation patterns and the extent to which gusts can be moderated on the windiest days.
  • Existing building projects will be studied to determine typical demands for ventilation and other factors controlled by the building envelope including daylight, solar gain and heat transfer by convection and conduction.
  • The 'art of the possible', determined by the CFD modelling, will be reconciled with typical building requirements and the realistic geometries, vent strategies and control strategies will be reviewed to determine rules for use at the outline design stage.
  Two reports will be written:
  • One for clients and architects presenting the information required to allow the inclusion of an effective double facade at the design stage.
  • The second for cladding and building services engineers presenting an engineering methodology, along with relevant data gathered as part of the project.

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