DAYLIT AREA Op-2

Afogreen Build, thank you for your reply, but you do not atrget my questions. 1. Do I need to take (= compare to threshold to get credit points) for all regularly occupied spaces 9AM or 3PM (whichever is lower, assessed at building level, the same point-in-time for all building) , or do I need to pick for each regularly occupied space 9AM or 3PM (whichever is lower, assessed space-by-space, that is some space can have lower values at 9AM and some other space can have lower value at 3PM, so that the result can be a mix between the 2 point-in-time simulations) ? 2. Moreover (and it would be first of all), should I take thw worst case scenario between 9AM or 3PM (for the entire building as a whole, or selecting the worst case between the 2 point-in-time for every single space, this dependent on the answer to 1. )  (this should be YELLOW line in very simple example I've linked),  OR  should I use points of the grid calculation area  that recieves illuminace 300-3000 lux for BOTH 3AM and 9PM (GREEN line in the linked example)? This is more restrictive (mathematical concept of intersection between two sets VS minimum of two sets -minimum globally or minimum locally, this points again to question 1.-) , but it is what "both" does mean to me . The issue is that many software tools seems to intend MINIMUM rather the INTERSECTION, (intersection is my interpretation,  as far I understand what is written in the reference guide) I would like to know the authentic interpretation to this requirement Thanks

I had reponse to an inquiry by USGBC. The right interpretation is the second one, as I tought, so INTERSECTION and not MINIMUM. FAQ section of this credit should be revised in the answer to question "If I’m pursuing Option 2 or 3, can I average the compliant square footage between 9 a.m. and 3 p.m. for a space and use the average as the compliant square footage?" That answer is misleading towards the authentic credit requirement    

I got the green light to share drectly excerpts from our email conversation.   My original inquiry to USGBC:

[... ] some opertaive clarifications will be really appreciate pursuing the credit through Option 2.

When asked to "record the areas that are daylit (have illuminance levels between 300 lux and 3,000 lux for both 9 A.M. and 3 P.M.) and the associated floor area" (reference guide, step-by-step guidance, option 2, step 3, 1st bullet point), do I have to refer to:

1. the minimum building area 300-3000 lux of the two scenarios (9AM vs. 3PM), that is to say to pick the 9AM results or 3PM results, wichever is smaller (yellow area of the schematic figure, please see: https://1drv.ms/u/s!AnOv3GbixKLFnb19KzA18jAPM16uIA?e=lfmyeV)

or

2. the intersection of building areas 300-3000 lux at 9AM and 3PM, that area the daylit area both at 9AM and 3PM (green area from the schematic figure above). This a more severe interpretation but may underline the concept that a desk station is not moving during the day; moreover it seems to me the literaly meaning of areas daylit "both 9AM and 3PM" [...]

    Here the reply by the expert:

[...] Per Option 2, Simulation: Illuminance calculations credit language (https://www.usgbc.org/credits/commercial-interiors-retail-commercial-interiors-hospitality-commercial-interiors/v41/eq121?view=language), the team needs to "Perform computer simulations for illuminance at 9 a.m. and 3 p.m. on a clear-sky day at the equinox for each regularly occupied space. Demonstrate illuminance levels are between 300 lux and 3,000 lux at both 9 a.m. and 3 p.m. Spaces with view-preserving automatic (with manual override) glare-control devices may demonstrate compliance for only the minimum 300 lux illuminance level."    So the second interpretation in your email appears correct. The area that receives at least 300 Lux at both 9 am and 3 pm should be listed in the calculator. If some of this area receives over 3000 lux, at 9am and/or 3 pm, then the team will also need to confirm that view preserving automated shades are installed for this area to demonstrate credit compliance. But if an area receives over 300 Lux daylight at one of the two times, but not both, then that area would not contribute towards compliance. [...] Yes, to confirm once again, any area contributing to credit compliance must have the required illuminance level at BOTH 9am AND 3pm.  [...]