I am confused by what seems to be contradictory information in the Reference Guide and what my LEED reviewer commented.
The comment says, "It is not clear whether the claimed daylight zones would be as large as noted in the calculator for the [specified rooms]. Provide floor plans that shows the daylight zones for each space used in the calculations. Along with the plans, provide sections showing how the depth of the zone was established."
When I go through the reference guide, the instructions never describe where a daylight zone is part of the equations. I see the "2H Daylight Zone" and "Modified Daylight Zone" indicated in Figure 2 on page 557.
However, in the method described on page 556 and 557, and also shown in Table 2 on page 558, the Floor Area (FA) is calculated with the full depth of the bay, in the example it is Bay Width 20ft and Bay Width to Core 40ft for an FA area of 800sf. The equation then calculates WFR=WA/FA and then VLT*WFR. The result of VLT*WFR is used to determine compliance. The spreadsheet provided (Supplemental Daylight and Views Calculation Spreadsheet) uses the same method, with one difference. The FA used in the spreadsheet is titled "Zone Floor Area" which is defined in footnote 2 thus: " Zones cannot overlap and are user defined based on the windows in the space. The zone size can be reduced as needed to increase the window to floor area ratio."
Nowhere in any of this does it require the calculation of a Daylight Zone as shown in Figure 2.
So, in my spreadsheet I have a room that is 859sf. The window area is 172sf, the Tvis is 0.64. I modified the Zone Floor Area to be 736sf, which results in a VLT x WFR of 0.150. The spreadsheet then includes 736sf in the Sidelighted Area Subtotal.
According to my reviewer's comments, I have done something incorrect and they want me to indicate the Daylight Zone on the floor plan. Have I done the calculation incorrectly?
TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
March 30, 2017 - 10:48 am
Remember this, the reviewer is not as familiar with the project as you are. They only have what you submit and how you submit it. So when you are questioned like this, its not the reviewer saying something is wrong, its the reviewer wanting clarification to confirm you did it right. Without seeing what all you submitted its hard to say whether the reviewer should have questioned this or not. Typically i see this being questioned where a project team is claiming the daylight zone area to be 100% of the floor area of the space and the space is very deep with a low ceiling. If your sections and plans have no dimensions, the reviewer may question the depth of the zone.
The zone floor area is established by the width of the bay and the depth of the daylight zone. The width is determined by whether there is different size windows or glazing within a room. Typically, the width is the length of the entire wall and people do not play around with multiple bays and different widths due to time and effort. The depth is established by either 2H or using the 63 degree angle. The area is established by the width and the depth. This total is then your total zone area.
So, provide a section, dimension it, use either the 2H or the 63 degree angle method and show it on the section. Provide a plan that highlights the total zone area for each space. As long as your original calculation of the total zone area was correct, you will need nothing else. However, if your total zone area is not correct, then you will need to provide a revised calculator and form. Its also good to provide a narrative telling the reviewer what you are doing and submitting.
Hopefully this clarifies your issue.
Kristian Kicinski
Associate Principal / Director of SustainabilityBassetti Architects
7 thumbs up
March 30, 2017 - 11:07 am
This is where it gets confusing for me. The reviewer is asking me to use the method you describe- a daylight zone calculated from the height of the window. But the equations and examples in the Reference Guide do not include this method. Table 2 uses 800sf as the FA for "N/S Bay". The dimensions listed are Bay Width 20ft by Bay Width to Core 40ft. If a Daylight Zone were part of the equation, then the calculated FA would be less than 800sf, because the window head is 10ft. It would be 20ft wide by 20ft deep, resulting in a FA of 400sf. That would result in a VLT x WFR of 0.30 and the bay would not qualify.
The instructions match Table 2. The instructions say:
-Determine the floor area (FA) for the typical bay- that is, the bay width multiplied by the bay depth to core.
-Determine the ratio of the window area to the floor area (WFR)- that is, WA/FA.
It does NOT say "determine a Daylight Zone based on the window head height."
TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
March 30, 2017 - 12:12 pm
Then you should make your argument to the reviewer. The reference guide and even the addenda does not provide enough information to properly use the prescriptive method nor the correct way. But every reference guide and credit never does and this is why we have Lis and addendas and people on forums like these.
The prescriptive method is simple calc based on ratios rules of thumbs established in daylighting practices and the old DF calculation. A designer can assume that a space will have sufficient levels of daylight within 1.5 to 2 times the window height. Hence the diagram on page 557 showing the daylight zone. This is based on CIE overcast sky model. Any deeper into the space and the access to the skyvault is at a point in which adequate daylight levels cannot be determined with simplistic calcs and more than likely will not have sufficient daylight levels. To use whatever distance to the core is can results in spaces achieving the daylight credit when they are actually over or under daylit.
Kristian Kicinski
Associate Principal / Director of SustainabilityBassetti Architects
7 thumbs up
March 30, 2017 - 12:32 pm
I understand the relationship of window head height to daylight penetration into the space. I'm not arguing the science. I'm arguing the methodology laid out in the Reference Guide, which requires a simple ratio of floor area to window area. The methodology does not include a consideration of window height compared to the depth of the space. I believe the reviewer is asking me to do a measurement and calculation that is not required in the Reference Guide. I'm posting here to test that argument before I respond to the comment, and see if others have had similar experiences. I'm surprised that in going through all the previous comments on this credit this hasn't come up. I've been looking for an addendum or update that clarifies the method and haven't found anything.
TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
March 30, 2017 - 12:50 pm
The complete addenda for EQc8.1 is not available in the online credit library. The addenda also no longer uses bay nor does it use the sample calculation that you are posing in your argument. It uses different examples, but as i noted it still does not clearly define the methodology.
Search addenda number 100000892 dated 5/9/2011.
I can send it to you if you private message me or you can search through the USGBC website for it.
Kristian Kicinski
Associate Principal / Director of SustainabilityBassetti Architects
7 thumbs up
March 30, 2017 - 7:16 pm
I have written the following responses to the reviewer's comments. I'm sharing them here for reference and discussion.
Comment:
"Provide floor plans that shows the daylight zones for each space used in the calculations. Along with the plans, provide sections showing how the depth of the zone was established."
Response:
For the Prescriptive Option, it is not necessary to provide floor plans that show daylight zones for each space, nor sections showing how the depth of the zone was established.
Refer to Addendum #100000892 Post Date 5/9/2011. The Prescriptive method for Sidelighting is described on pages 556 and 557. The method does not include a calculation or establishment of a “daylight zone” related to the head of the window. The calculation uses floor area (FA) in the equation.
Comment:
"For spaces with exterior overhangs, especially those adjacent to the driving range, a 63 degree angle must be used from the bottom exterior edge of the overhang to establish depth of the daylight zone."
Response:
Nowhere in the Prescriptive instructions is this required. The 63-degree angle is mentioned only in context of determining eligible window area (WA) in relation to ceilings. Exterior overhangs or shading devices are not mentioned in the documentation. It is not used in determining floor area (FA).
The addendum reads:
"Determine the eligible window area (WA) for the space.
• Determine whether a modified head height must be used. As shown in Figure 2, draw a 63-degree angle from the vertical, in section, from the window head to the floor. If the ceiling obstructs this line, a modified head height must be used.
• Draw a 63-degree angle from the vertical, in section, using the ceiling corner that obstructed the previous line as a starting point. The point at which this line intersects the window is the modified head height. If a modified head height is used, count only window area below the modified head height. See Figure 2."
To further support this, Figure 2 on page 557 is titled “Sample Modified Window Head Height”. The Figure 2 included in the Addendum further clarified this from the original credit language by removing the words “daylight zone” from the diagram.
The addendum goes on to instruct:
"If the result is between 0.150 and 0.180, the space counts as a daylight zone. If the result is between 0.000 and 0.150, a portion of the space is compliant. Calculate the compliant floor area as follows:
• Divide the calculated result by 0.150 and multiply by the floor area of the space. This fractional result represents the floor area to be counted as qualifying daylighted area."
Refer to the uploaded Supplemental Daylight and Views Calculation Spreadsheet. Line 13 for Space ID 101-Pro lists the Floor Area as 859. The Zone Floor Area is listed as 736 because this is the fractional result from the calculation highlighted above, resulting in a VLT x WFR of 0.150.
Comment:
"Provide the type of glare control device installed in each regularly occupied spaced by completing the column labeled Glare Control Type in the calculator"
Response:
The Supplemental Daylight and Views Calculation Spreadsheet requires Glare Control Type to be specified only when VLT x WFR is greater than 0.180. All of the areas listed on the submittal have a VLT x WFR equaling 0.150, which is less than 0.180.
In conclusion, we maintain the documentation as submitted meets the requirements of IEQc8.1 Daylight and Views – Daylight; Option 2 – Prescriptive.
Deborah Lucking
Director of SustainabilityFentress Architects
LEEDuser Expert
258 thumbs up
March 30, 2017 - 7:51 pm
If you have your project in REVIT, (2016 and later), there's a nifty daylighting analysis tool using the Insight 360 plugin. We have been pretty successful with this.
TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
March 31, 2017 - 8:42 am
I'd say that the reviewer would buy your case with the daylighting zones. But I'd take one space and do it as the reviewer notes and show that the space would still meet the requirement regardless. That's my opinion but its not my project or time.
If you have any exterior overhangs that will impeded access to the sky vault you need to use the 63 degree angle. So any case where you have ,say an exterior shade, you will have to use the 63 degree angle. I've read your argument, i know the guides and addenda but you are not accurately using the tool and i believe the reviewer may disagree with you.. Argue with GBCI for poor instructions but that is my professional opinion.
Glare control devices are required regardless, states in the reference guide. If you have a ratio higher than 0.18 you can use automated shades to still earn the credit. An since there is nothing listed in regards as to what is defined as high contrast nor a reference to contrast an argument in regards as to what is considered high contrast or contrast in general will lie on your shoulders an you will have to provide a lot of info to demonstrate that there would be no high contrast anytime for any occupant in any space. Exterior shading devices can be glare control devices. Look, if you got blinds or shades note them in the calculator and move on, otherwise i believe you will loose your argument for this and will end up with an appeal.
Good Luck.
Kristian Kicinski
Associate Principal / Director of SustainabilityBassetti Architects
7 thumbs up
March 31, 2017 - 10:55 am
Thanks for the feedback!