We are in the process of completing the spreadsheet for credit IEQ 8.1 for a NC project. Kalwall skylights are being used, in addition to Solatube 330 DS daylighting systems. However, the calculations are showing that the skylight coverage is not between the 3% and 6% range. What is the rationale behind the values falling in this range? Kalwall daylighting systems are often significantly larger than 6% of the floor area but we get no credit for them if they are too big. Any suggestions besides removing the Kalwall system to qualify under the prescriptive method?
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Eddy Santosa
Director of SustainabilityDBR Engineering Consultants
376 thumbs up
August 4, 2011 - 2:09 pm
Do you have a daylight consultant in your project? If you don't, I would suggest you to hire one. The daylight consultant can advise the correct sizing for your skylight and solatubes. 3%-6% is optimal skylight design to get sufficient daylight and energy reduction. If you put higher than that, you will not gain the benefit of the daylight because your energy consumption is higher. Additonally, there are many good readings in "resources" tab above.
Jason Levine
10 thumbs up
August 4, 2011 - 6:42 pm
We do not currently have one but I will definitely pass this along to my boss. Thank you for the response.
Brian Baewon Koh
CEO, former USGBC FacultyInnovative Design, Inc.
12 thumbs up
August 7, 2011 - 6:00 pm
I second Eddy's recommendation of getting an expert's help. However I have to add that the prescriptive guide of 3-6% of floor-to-skylight ratio doesn't work well in some climate zones. Although the light level from the 3-6% might be proper, in many cases, the heat gain becomes too much that it negates one of the big advantages of daylighting - energy saving. Also the daylighting level depends on many other elements such as ceiling cavity depth, color of the light well, etc. I strongly recommend not rely on the prescriptive method. This is why LEED 2012 proposed to remove it if you look at the LEED 2012 2nd public comment version available now.
Adrienn Gelesz
LEED APABUD Engineering Ltd.
48 thumbs up
April 4, 2014 - 11:53 am
HI, for toplighting, is the requirement 3-6% of total space area, or 3-6% of toplighting zone (caluculated by the 35degree line, etc)?