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NC-2009 IEQc8.1:Daylight and Views—Daylight

0.5m margin and work-space adjacent to the glassed facade

Hello, For dayligting simulations, there is usually a 0.5m margin applied around the perimeter of the room, excluding the area from the assessment. In our understanding, this is because of potentially misleading illuminance values so close to the wall (i.e. influence of vertical surface reflections) and also because of the assumption that there are usually no work spaces that close to the wall. However, in our project (office building), there are workstations adjacent directly to the glased facade. If we apply the 0.5m margin, a great part of these workstations within the ROA would be excluded from the assessment. Would that be acceptable to set the margin to 0m while providing an explanation in a narrative?

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Profile picture for user treed74
TODD REED
Energy Program Specialist
PA DMVA
LEEDuser Expert
626 thumbs up

Tue, 08/09/2016 - 12:21

Run both and compare. I'm betting it does not effect credit achievement. Personally i run my calc points right up to the wall and have submitted multiple daylighting reports like that and have never been questioned.

Tue, 08/09/2016 - 14:29

Thank you Todd for the quick reply. I agree that to do a comparative study would be ideal, but unfortunately we are pressed by time and the simulations are quite time consuming. But I understand that you haven't had a problem with no margin at all, so will use this option. Next to the original question, I would also like to confirm my understanding (sorry if that would be better to start a new thread, I can re-post if you would prefer so) - following the LEED guidance, the maximum allowable grid spacing is 5ft. In our software (IES VE) the default spacing is 0.5m. I am thinking about increasing this value as I assume that the simulation will be faster. I guess that this will be acceptable, even if the reviewer may know that the software can simulate at higher resolution. But ideally, I would like to avoid any questions later on. Can I ask - what resolution do you usually simulate with (office buildings with open, as well as separate offices)?. Is this something I should be concerned about?
Profile picture for user treed74
TODD REED
Energy Program Specialist
PA DMVA
LEEDuser Expert
626 thumbs up

Tue, 08/09/2016 - 14:39

Set it at 5 feet and run it, this will be fine for LEED documentation. If you were doing this during the design phase, i would set it a little tighter, but that is my own preference and situation dependent. When you submit, you will include a narrative that states all your simulation parameters, reflectances, grid height and spacing, times of day, etc. A reviewer is not going to try and determine whether you are at 5 feet or 4 feet. If you include the illuminance levels on the sim output image, you'll need the spacing to allow the clarity of the text, program dependent. A reviewer would probably question a space that is 20x30 and only has four calc points shown. Fewer calc points do tend to lead to quicker calc times, of course many other factors can make sims slow, but with everything right, it should be quicker. The biggest thing you should focus on is consistency. Ensure whatever information you have submitted is consistent between all other documentation in other LEED credits. Make sure the room names and numbers are the same between sim reports, floor plans, and daylight calculator, Make sure the areas are the same. Make sure the numbers in the calculator much the numbers in the credit form. Make sure your ROA matches the number in PIF2. Provide a narrative as to what you did, make sure it can be read, and you should be fine. A reviewer is not there to find fault, even though some believe that is what they do, they are there to ensure that "you" have demonstrated that your project has met the requirements. You'll get the benefit of the doubt if you are honest, consistent, and demonstrated that you a general concern for the submission process. Being sloppy, inconsistent, and not providing the minimum will tend to sway a reviewer away from the benefit of doubt.

Tue, 08/09/2016 - 15:53

Thanks a lot for this detailed answer Todd, this is really great. This is our first dayligting project taking the simulation route, so your support is really appreciated. Thumbs up!! :)

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