How does E+ determine wind pressure coefficients on surfaces that face an internal yard within the building?

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We model a rectangular building with an internal yard (open to the sky) and windows facing this yard. In order to evaluate the effect of natural ventilation we run the fully calculated ventilation option. From the Engineering Reference document, it is not clear how E+ treats the wind pressure coefficients on the surfaces that face the yard. It seems that it will use the same coefficients as it uses on the externally exposed surfaces in the same direction, which is not correct, and would cause wrong patterns of air flows (i.e. air flow into the building on the surface that faces the wind direction instead of outflow as should be on all the surfaces facing the yard).