I am using sketchup and Daysim for daylight simulation for a school project. My results give me daylight levels for every hour, every day of the year. The results are abnormally low on Sept 21 and 22 compared with most of the days in September. It looks as though Sept 21 and 22 must have been very dark cloudy days when the weather file I am using was created. Should I use the results for Sept 23 and explain my reason for doing so as an alternative compliance path?
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TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
June 22, 2011 - 9:38 am
Caroline,
What is your step set to in Daysim? In Daysim you can set the time step to have the program look at the weather from every 5 minutes up to every 60 minutes. By setting it to 60 minutes you'll decrease your simulation time and you may get results that are closer to clear sky conditions.
You may need to really explain your methodology to the reviewer on this. Just stating that you got better results on those days will not cut it. The reviewer may not be as familair with how Daysim works as you so you will need to justify the results. I would dig in the weather file and look for those 3 days, pull out the sky illuminance for those days. Use that information to show the reviewer that clear sky conditions for the projects location has an illuminance of ( ) and typical cloudy conditions have an illuminance of ( ). Based on the average illuminance of those days, the date you use is closer to clear sky conditions for the site. You may have to add some fcs to your calcs since how daysim is looking at weather conditions and there are times in there which are cloudy. State that those days are closer to clear sky conditions than the 21st.
For this version of LEED it requires clear sky conditions to demonstrate compliance, this is because it requires projects to consider direct solar impacts. If the 2012 daylight credit were a pilot credit, you would have an easier time. The reviewer could deny it because the calculations where not done under true clear sky conditions.
I have only played with Daysim plugin for Sketchup and not sure if it allows you to run radiance and import the radiance results. This would be better for this version of LEED.