[bldg-sim] Energy-10: Light shelves and shading?

Rob Hitchcock RJHitchcock at lbl.gov
Tue Apr 13 14:13:14 PDT 2004


Caroline,

I'm afraid that within the constraints of the Energy-10 user interface, 
you will not be able to effectively model your lightshelves.  The 
shading overhangs that can be defined within Energy-10 will only block 
light from reaching the window below the overhang.  They will not 
reflect light up through the window above them.

Using a high ground reflectance to approximate the upward reflection of 
light from a light shelf is at best only that - an approximation.  It 
will also incorrectly cause additional light to reflect into the lowest 
window, which is typically the largest glazed area, probably causing a 
larger error in your final results than you would get with a more 
accurate ground reflectance.

Rob Hitchcock
===========
Caroline Prochazka wrote:

>I am a graduate student of architecture at the
>University of Waterloo. I am using Energy-10, Ecotect
>and Desktop Radiance to study the role of daylighting
>with respect to heating and cooling energy for two
>existing Canadian 'green' buildings. This posting is
>only one of my many questions, which recently arose
>from closer examination of my models.
>
>ENERGY-10: A question about shading. My south facade
>has two shading elements for each window unit,
>dividing the windows into three portions. Top-down
>there is one exposed area with a light shelf
>underneath, this lightshelf is an overhang for the
>middle glazed area with another light shelf below
>that; finally there is a slightly larger glazing area
>under the second light shelf with vertical wall under
>that. To simulate this shading, is it more appropriate
>to break up the south windows into three types (Top
>pane with no shading, middle pane with shading above
>and lower pane with shading above)? or to figure out
>some sort of equivalent, larger, overhang to position
>at the top of the original window unit, and forgo the
>effect of the small unshaded top portion? Alternately,
>it has been suggested that I use a high ground
>reflectance to simulate the light shelf.
>
>Regards,
>Caroline
>
>=====
>t.    519.822.3832
>e.    cjprocha at yahoo.com
>web:  http://www.geocities.com/cjprocha
>
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