[EnergyPlus_Support] Re: Residential Multifamily Infiltration & Ventilation

["Jean marais" <jeannieboef@xxxxxxxxx>]

This is my personal most loved debates. IMO crack infiltration is well addressed with the infiltration objects available in eplus. The take into accound the primary driving force, namely wind, as well as other miniscule effects like stack effect and temperature difference.

But as soon as you have a building primarily thought to ventilate with windows, then you enter the realm of "natural ventilation". The air movement through large open spaces like open windows is erratic and unpredictable. How do you know when occupants will open windows, wind direction, gusting, temperature differences, stack effect...these all play major roles now depending on the moment's conditions. CFD is also just a clip in time. How to simulate this over a year to get "equivalent" energy gains and losses caused by natural ventilation?

COMMIS and Air Flow Network were developed around the same time and use mainly the same theory. CONTAM was a iSBAT user interface developed by NIST for COMMIS. I like using AFN because it so tightly nits with the built environment which one can create with eplus. The AFN has flexibility to predict window opening and modulation based on indoor and outdoor temps, fresh air requirements (both which help predict when occupants may choose to open windows). IMO it still lacks a manager that will close windows if the air velocities through the window exceed set limits (this can be done with ems, but is not feasable for large complicated buildings).

I have asked DesignBuilder to think about developement of graphical results displays similar to CONTAM and an interface to build or edit the autogenerated AFN it currently does.

However you approach natural ventilation, there a huge limitations, assumptions and approximations. This in one of the largest question marks regarding modelling on my list.

And that is my opinion.



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