[BLDG-SIM] atrium natural ventilation

Nick Doylend bldg-sim at ndoylend.fastmail.fm
Thu Oct 18 02:27:49 PDT 2007

Hi, I wonder if anyone can give some advice on this one.  My colleagues
and I are considering a naturally ventilated atrium in the UK.  We're
trying to establish appropriate opening areas at top and bottom to limit
summertime overheating conditions.  At the moment we are using Tas for
this analysis but now suspect its bulk air movement calculations
are not sophisticated enough to model the stratification in the space.

The atrium is occupied at the ground floor and extends up four stories,
it has been zoned into four horizontal slices.  Rather than showing an
increase with height of air temperature we see the opposite - the lower
zone is warmer than the upper zones.  Maybe the ground floor zone has a
higher sensible gain due to the occupants but in a high vertical space,
shouldn't the heat rise to the top of the space?  I wonder if Tas is not
considering the convection across the horizontal zone boundaries or is
overestimating the downward air circulation?

Does anyone have experience of using Tas or alternative techniques for
this kind of analysis?  We would prefer to run a dynamic simulation that
can predict annual overheating, rather than a detailed CFD snapshot in

Any suggestions?


Nick Doylend

PS It would also be interesting to get a show of hands from the Tas
users on this forum - eQUEST seems to be the most popular simulation
tool here judging by the volume of posts.

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