Daylight Analysis

Worst case compliant area is what you use. So 73%.

Because the reference guide states, the area that meets the minimum illuminance requirement at both 9am and 3pm. This requirement was discussed within the TAG and working groups, and then voted on by the public, so it is the requirement.

Allowing projects to use the average would allow some projects which have poor daylighting condition at certain times of the day to earn the credit. The intent of the credit is to ensure the occupants are provided adequate illuminance values and good daylighting throughout the occupied times of the day.

If you are going to use daylight in your project, then you set your daylighting performance goals at the beginning of the design and then you ensure that the design meets that goal.

Todd,
could you please clarify, as I have read mixed messages on this. I understand that the worse case between 9AM and 3PM applies. But is it:

a) worse case for the building as a whole (i.e. 73% at 3PM < 85% at 9AM - figures for the whole building)

or

b) worse case (between 9PM and 3AM) for specific rooms in the building, which then then make up the total percentage? (e.g. ROOM_01 69% at 9AM < 76% at 3PM = ROOM_01 worst case is at 9AM, but ROOM_02 83% at 9AM > 72% at 3PM = ROOM_02 worst case is at 3PM --> total daylighted area = ROOM_01 at 9AM + ROOM_02 at 3PM)?

It is b. So, as fill in the daylight and views calculator to document the credit. You will list the individual spaces and include the worst case value for each space, be it 9am or 3pm. The only way you should group anything is when you have similar floors. Then you can extrapolate the results of one floor for the other similar ones. Do not group spaces. Even if the same room is side by side, you need to list them individually.

Thank you Todd, it is clear now. Is it possible to develop / submit my own version of the calculator sheet that would automatically take care of the selecting worst case between 9AM and 3PM for each space (i.e. after loading with the data from software from both simulations) and then report the final figure? Or should I perform the comparison else where and then report just the final column in the dayligth calculator? I am asking as my colleagues commented that if the reviewer sees a tool he/she is not familiar with, it may actually work to my disadvantage. Or can I submit both? Thank you for any comments / thoughts on this

The answer is yes. I have submitted my own spreadsheet many times because i do not like the new one not having either of the times listed as in previous versions. Just ensure you include the same things like room names, SF, etc. etc. Make sure your calculations are right. I also include a narrative stating that i am including my own calc. Also, i make sure that i upload it as xls format so that the reviewer can check the formulas and see that I'm not playing around with the numbers.

In regards to the reviewer, any reviewer who would not understand a spreadsheet that is almost exactly like the calculator probably should not be reviewing the technical aspect of the daylighting credit. Like i noted, i have never had an issue with my own since it includes everything the calculator does along with some extras. But upload it as a xls format so that the reviewer can confirm your formulas. If you upload as PDF and they see something fishy they will question it.

Thanks Todd. This has been very helpful

Hi all,

I posted on this recently and can no longer find my comments... perhaps lost in the BuildingGreen upgrade.

I'm still having trouble figuring out why the LEED reviewer is asking for us to "revise the spreadsheet to ensure that only the area that is compliant at both 9 a.m. and 3 p.m. on September 21st, not at one time or the other and not the average compliant area, has been reported as meeting the daylight requirements." When we've spoken with AutoDesk (as we used their Insight plug-in to develop our simulation), they said:

"The reviewer is wrong in their interpretation of the 9am/3pm requirement, as it seems they are asking for point-by-point aggregation of the two hours (points where both 9am and 3pm thresholds are satisfied). We initially implemented LAR with point by point aggregation, showing points that satisfy both, but that's not how it was supposed to work, and since the full release, it's done room by room. The criteria is not point by point, but room by room. "

And:

"I would urge them to look for reviews showing proof of that interpretation. It's a common misunderstanding."

How am I supposed to proceed here? Do any modeling tools output what the reviewer is asking for? Should I post this again somewhere else? I am hitting dead ends.

Thanks,
Hannah

Hi Hannah - I have always done the calculations they way the Reviewer asks, which is as it is stated in the LEED Reference Guide. Unfortunately, I have not seen any simulation software that will overlay two simulations and tell you the areas that are compliant at both simulation times. For a lot of rooms, I imagine the 9AM and 3PM areas overlap pretty closely. But, for those that don't, I overlay the images and do my own area take-off to determine the overlapping compliant areas. Yes, it is extra work for you. Autodesk needs to step up and provide software that can do the full calculation as LEED requires!

Erin,

Do you simply visually compare the 9am and 3pm for each space, and only overlap the obviously different ones? Do you do this through Photoshop? Area takeoffs in something like Bluebeam? We're desperately trying to figure out how to complete this without wasting time.

Thanks!
Hannah

Yep, that's exactly what I do. I usually import the simulation images into CAD or Revit. Then do area take-offs for the rooms where the 9AM and 3PM daylit areas are clearly different. Photoshoping the two simulation times to extract the overlapping images can help identify the overlapping areas. Bluebeam would be a good tool for getting the areas from the image files (I don't have Bluebeam, but it would be perfect for this task).

Thanks so much, Erin! Now that I'm comparing side by side it is definitely easy to see when I will need to do some annoying analysis versus being able to just combine data points from each time, or pick the more stringent, etc.

Best,
Hannah