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Standards Section 140.3C error when doing NewEnvelope analysis

asked 2017-03-06 16:59:22 -0500

Skobunny's avatar

I'm doing a preliminary envelope study via Sketchup/OpenStudio in CBECC-Com 2016 for a retail building (2 stories, 38000 SF). However, I am getting errors related to CEC Section 140.3(c) because I have two large spaces over 5,000 SF that don't meet the minimum daylighting requirements, which is preventing me from running an envelope-only analysis. I do not have any lighting systems fully-designed/modeled yet, but is there a workaround for this issue?

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answered 2017-06-21 22:30:50 -0500

updated 2017-06-21 22:31:10 -0500

This has been an issue in CBECC-Com for a long time- the developers added this as a performance requirement, as Greg stated above, even though it is actually prescriptive. I remeber having an exchange about it awhile back but don't recall the reason that they gave for including it in this way. The way I have gotten around it is to place a skylight in the model with a SHGC of 0 and a U-value equal to that of the roof.

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answered 2017-03-16 14:59:27 -0500

Section 140.3(c) is more about adding skylights than adding lighting/daylighting controls. If you read the Standards, you'll see the requirement is triggered for spaces "that are greater than 5,000 ft2 and that are directly under a roof with ceiling heights greater than 15 feet..."

That's a PRESCRIPTIVE requirement, however, so you should not be getting an error when performing a PERFORMANCE analysis, so it's a software issue. I'm not sure which version of CBECC-Com you're using (code year or software version), but you could try updating to a newer version if there's one available and see if they fixed the issue.

Alternatively, change the height of your space to 14.9 feet and the error should go away (although your baseline will be altered as well, which is technically incorrect).

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Asked: 2017-03-06 16:59:22 -0500

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Last updated: Jun 21 '17