For LEED 2009 EQc8.1, if small space has one exterior wall completely glazed, and according to the prescriptive method , VTL*(WA/FA) >.18, then would automatic shades for glare control be an argument for meeting this credit. The project I am dealing with consists of several rooms with lot of glazing in order to maximize the use of daylight, but obviously would have glare issues. Is automatic glare control acceptable to meet the requirements?
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Jill Dalglish, PE
Lighting EngineerMKK Consulting Engineers
LEEDuser Expert
440 thumbs up
June 9, 2010 - 11:50 am
Neetu,
Thank you for your question and your interest in LEED and daylighting. Please consider that as a sustainable practice, the design you describe is not recommended. A lot of glazing does not (necessarily) maximize the use of daylight and it also does not benefit energy efficiency (as you probably know). If I do say so myself, I think you might benefit from the services of a qualified daylighting designer. I happen to know someone who is available. ;)
To answer your LEED question, I believe the answer is no. Since the calculation is greater than the maximum, it does not qualify. To qualify, you need to be within the minimum and maximum AND have glare control. The fact that it is automatic does not except you from being over the maximum.
Neetu Singh
Building Performance AnalystThe Green Engineer
June 9, 2010 - 12:25 pm
Thank you Jill for your reply. I agree that maximizing daylight does not necessarily benefit the design.
Let me reiterate my question here.
The overall design of the building is to let in daylight into deeper and wider spaces of the building. As a result of this effort and the related design aesthetics some of the smaller rooms on the perimeter see more daylight than required. Important fact that I forgot to mention was that the entire glazed facade for this project is screened by terracota screen for shading purposes, to avoid glare and entry of direct sunlight into the spaces. Sadly enough, Option 2 of LEED, the prescriptive approach does not take into account any kind of permanent shading while calculating the VLT*WFR ratio.
I had my doubts because if the project is not willing to go the "simulation" way to achieve this credit is there no other way to document that glare control measures have been taken into account.
If hypothetically I placed automated shading devices in the small rooms which had too much of daylight, it would actually be preventing any discomfort during the use of that space as the shade control would not be occupant dependent but rather glare dependent.
Would the space then not qualify for the credit?
Jill Dalglish, PE
Lighting EngineerMKK Consulting Engineers
LEEDuser Expert
440 thumbs up
June 9, 2010 - 12:51 pm
I see, this does explain the intent more clearly.
I would argue that your terracotta screen reduces your effective VLT. I would show calculations of your Effective VLT in your supporting documentation (VLT x %openness factor of the screen) and use that for your VLT*WFR calculations and see if you comply that way. It's a bit non-standard and I don't know if GBCI would go for it. How far from the glazing is the screen? Are there angles of the sun where direct sunlight can get around the screen?
I would again say that the automatic shading of the small rooms (although good for the design) would not exclude you from exceeding the maximum ratio because it is not permanent. I don't know if the reason for having a maximum VLT*WFR ratio is to prevent glare or some other reason. Arguing for good glare control may not apply if there is some other reason.
I'm getting into a fuzzy area here and don't have direct experience with modifying the VLT to be an Effective VLT so I'd be happy to hear what others have to say.