Sorry for the late response here and very good observation. In honesty, I never quite realized how the opening multiplier values were supposed to work but what you have said makes complete sense. It was easy enough to add an input for these opening multipliers in the case of shades so I just added it into the component:
Hi @LachlanFinn and @chris,
I am trying to carry out a parametric analysis with the shade to glass distance and I bump into these four parameters Top opening multiplier, Bottom opening multiplier, left-side opening multiplier and Right side opening multiplier. In the last version HB 1.6, these parameters are left as 0.5 per default. Does this mean that half the distance from the window is open to the airflow to all sides?
Figure shows examples of Abot, Atop, Al and Ar for different shading device configurations. These areas range from zero to a maximum value equal to the associated shade/screen/blind-to-glass cross-sectional area; i.e., Abot and Atop ≤ sW, Al and Ar ≤ sH.
I’m not an expert on how exactly to translate the real opening area into the the multiplier that EnergyPlus uses but I think that your understanding is correct from what I can tell:
Going off figure (b) on the right, I think a multiplier of 0.5 would mean that distance b is half of distance s.
It may help to know that I really have not seen the opening multipliers affecting my simulation results much unless I set them all of the way to zero and I also set the shade permeability to zero. At that point, you have the air trapped within a gap between the shade and the glass. Otherwise, the difference between a little air circulation and a lot is not usually that significant.
