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# Read Daylight Metrics CSV Files

Can someone explain me how to read the Data of DaylightMetrics?

For example : What the meaning of Daylit, Daylit occupied etc.. and how the numbers come?

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Short Answer: If you had a space that was routinely occupied well into the evening, or conversely vacant for half the day, the metrics would potentially tell the wrong story, is all.

Longer Answer: The reason there are three values for each daylight metric (sDA excepted) is there is no prescribed temporal range for them. The OpenStudio Radiance measure just calculates for the three most interesting ranges, daylit, occupied, and "daylit and occupied". It's obviously pointless to calculate the daylight metric for nighttime hours, we know that is zero, right? But depending on the space type, it may be more useful to calculate the daylight metrics for when a space is known to be in use. We know the occupancy status from the occupancy schedule that is part of the OpenStudio model, and the daylit hours from the weather file, and the interior daylight illuminance from the Radiance simulation. From there we simply calculate the metrics, based on these three temporal input ranges. sDA has a specific range as dictated by IESNA (LM-83-12) for now, so that one we calculate accordingly -- just the one way.

As for the other elements in the data:

metric_value - this is the metric. I don't know how to make this any clearer.

hours_met - number of hours where the metric criterion was satisfied. In your example, this would be the number of hours where the daylight illuminance was >= 500 lux (for DA and conDA) or >=100 <=3000 lux (for UDI).

input_hours - number of hours that met the criteria for consideration, i.e. were either daylit, occupied, or (daylit AND occupied), per column 'C' in the dataset.

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how about the Metric Value, Hours_met, Input_hours meaning? i dont get that

( 2016-08-15 22:50:04 -0500 )edit

I updated the answer. Again, the "metric_value" is simply the metric. It's the percentage of the input hours that received enough daylight to satisfy the metric criteria. Make sense?

( 2016-08-16 11:12:03 -0500 )edit