i am entering data, and have a small room with wide windows that push the number to .26. Based on what I have investigated, I need to adjust the daylight zone (in this case up) to get it within the range. This is a defined room, it does not make sense to increase the daylight zone larger than the room itself. in reverse, i could theoretically reduce the window size to get within range, so it appears i am punished for a large set of windows? i first thought it may be trying to prevent too bright of spaces, but isn't this what documenting glare control devices is for? what am i missing?

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TODD REED

Energy Program Specialist

PA DMVA

LEEDuser Expert

626 thumbs up

Mon, 09/12/2011 - 17:29

Your not missing anything, what you are getting is the frustration with the prescriptive method. It is a formula, that does not consider climate, site orientation, interior reflectances, etc. It is meant to be used by projects, and you are correct, to reduce over or under daylighting space. Projects that ignore all apsects of daylight and create glass boxes will have a hard time meeting the prescriptive path. We have projects that meet LEED requirements through simulation, and actual measurements that would not have earned the credit using the prescriptive path. If we would have designed the space to meet the prescriptive path requirements, it would actualy be under daylit. North facing spaces in cloudy climates require more glazing and higher VLTs. If you truly want to daylight a space, then simulations or models is the best option. Have you tried multiple zones in a space

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FAQs about IEQc8.1 :

IEQ 8.1: VLTxWFR - why the upper limit of .180?

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