We are trying to use the prescriptive method for an industrial Project which is planning to incorpórate a "shed" type roof which has horizontal glass on on side . Sincé it is in the roof, it is a skylight, but since the Windows are vertical they are tecnically to be considered Windows. Can we use the prescriptive model for this?
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TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
February 12, 2013 - 9:26 am
Emmanuel, are these clerestory windows? Just trying to picture what this scenario is. Too bad you can't upload a sketch on here to show what is going on.
Without seeing what is going on, i would say that you can;t use the prescriptive method to document clerestory windows that are located within the roof area. The reason being is that the prescriptive method is very limited and its only really meant for prescribed scenarios. The methodology is based on how much of the sky dome is accessible through an opening. That is why you use 2H or the 63 degree angle to establish the depth of your zone, it is also why with skylight you use 35 degree angles. Its all about access to the sky. Clerestories are great daylighting strategies which, depending on their orientation, can provide some great reflective and indirect light into a space.
To say that your daylight zone is the area that is defined by drawing a line straight down from the glazing surface and then the depth would be what? If the clerestories are really high, you couldn;t use 2H because leading edge of the zone technically has no access to the sky dome and the prescriptive method can;t be used for reflective strategies. Drawing a angle from the head of the clerestory window using the 63 degree may result in a realistic daylight zone, but if the windows are really high, the angle would create an unrealistic zone.
You can;t really use any of the steps in determining the daylight zone from skylights because the clerestory glazing is vertical, and not horizontal.
Without being able to establish a zone, you can;t demonstrate the ratio. Without the ratio, you can;t document the method.
Emmanuel Pauwels
OwnerGreen Living Projects
137 thumbs up
February 12, 2013 - 9:43 am
Todd,
Thanks for your reply. The Windows are indeed clerestory Windows on the roof. The height of the área is 10 meters which is high. One part of the roof has curbed skylights. I guess we can count those, right? Other part of the roof are those clerestory Windows which as you explained can not be validated with the prescreptive method. A 35º angle from the opening in the roof would cover a very large zone, so I do not think that is realistic.
TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
February 12, 2013 - 9:52 am
Your curbed skylights can be used in the prescriptive method. If this is already built, then just use measurements, otherwise simulation is the best way to go. If your just trying to earn the daylight credit without wanting to know performance then you could use the prescriptive method, minus the clerestories.
Emmanuel Pauwels
OwnerGreen Living Projects
137 thumbs up
February 12, 2013 - 10:16 am
Thanks Todd. Even when the height is 10m can I use the curbed skylights in the prescriptive method. Is there no height limit?
TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
February 12, 2013 - 10:41 am
There is no height limit, but there are the other requirements that must be met as noted in the Reference Guide.