Window Downdraft - [source code]

Use this component to compute the floor-level downdraft air temperature and velocity at a given set of points that are located close to a cold surface such as a window. The draft conditions produced by this model are assumed to be 10 cm off of the floor. The model used in this component comes from physical measurements of window downdraft that were further validated using several CFD experiments. Ther are published in these papers: Heiselberg, P. (1994). “Draft Risk from Cold Vertical Surfaces.” Building and Environment, 29: 297-301. Manz, H. and Frank, T. (2003). "Analysis of Thermal Comfort near Cold Vertical Surfaces by Means of Computational Fluid Dynamics." Indoor Built Environment. 13: 233-242. -


  • testPts [Required]
    The test points at which downdraft conditions will be evaluated.
  • windowSrfs [Required]
    Breps or Surfaces representing the window surfaces off of which downdraft flows.
  • winSrfTemp [Required]
    A number representing the surface temperature of the windows in degrees Celcius.
  • airTemp [Required]
    A number representing the air temperature of the room in degrees Celcius.
  • defaultVeloc [Optional]
    A number in m/s that represents the speed of the air that is not in the downdraft. The default is set to 0.05 m/s.
  • runIt [Required]
    Set to 'True' to run the component and claculate downdraft conditions.


  • draftAirTemp
    Script output PPD.
  • draftAirVeloc
    Script variable downDraft
  • airFlowPlanes
    Script variable downDraft

Check Hydra Example Files for Window Downdraft

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