HB+ sDA Calculation - 2% of points

I’m having trouble understanding how HB+ performs the sDA Calculation. Per IES LM-83-12 (and explained when hovering over the blind_states_ input) the model must close the blinds when more than 2% of analysis points receive direct sunlight. I would understand “direct sunlight” to follow the ASE threshold of 1000lx direct (0 bounce). However, the blind_states_ input is from the blind states of the Dynamic Blinds Schedule, which are based on a single sensor point and the total illuminance at that point, not the direct sunlight. Even if the DynBlindSchd logic input is based on ill_dir, the shading schedule still only operates on that single sensor point rather than being triggered by 2% of all analysis points.

What is my best course of action if I want to do a by-the-books sDA with the shades being fully open when <2% points receive direct sunlight (>1000lx ill_dir) and fully closed when >2% points receive direct sunlight? Thanks!



Hi Riley,

There is an “ASE” component that to my knowledge will trace the hours of direct sun. The 0 bounce might be a bit off if it’s based on DAYSIM which will mean that your blinds potentially are down too often.

Hi @Riley.Johnson

I am using “honeybeeplus hourly values” component to generate blind state which meet IES 2% requirement.
As below screenshots (there are two window groups in this model), we can get number of points which exceeds 1000lux direct sunlight per each hour to define if the blind need to be closed or not, then we can make a customized blind state data-set which can be connected to the sDA component.

I believe I share the same question with @Riley.Johnson, which I think has been partially addressed but not directly answered. To me, the way sDA appears to be set up is that the dynamic shading receives input from a single sensor point. However, IES LM83-12 states that to be officially sDA, it needs to be >2% of the points over 1000lx for the dynamic shading to react. Does the sDA module (where everything connects to generate an sDA value and the DA grid) take into consideration the >2% points on the grid? Or is the sDA value based on the single sensor point, and to generate a “true” sDA, one would have to write something similar to what @gogog has written, as shown in his screenshot? Thanks,

Hi, @ldolezal
I think that sDA module is calculating the results based on blind state which it received, if there is no data connected to the component, it will only consider “the window” state. Of course, it need to be clarified by the develop team(@mostapha @chris). Moreover, as 2% points can be any point of the analysis gird, it is also hard to define the sensor point with native honeybeeplus component. Therefore, I am trying to solve this issue with the mentioned method in previous reply.

Why difficult to pick your point? Check all the points and see if more than 2% of your points receive direct sun where the direct illuminance is higher than 1000 x VLT value. That should set your blinds schedule.