coated double glazed window material in ecotect for daylight

[prerana_tuladhar]

I am currently working on a project where the building envelope includes double glazed coated window opening which greatly affects the amount of day light entering the interior spaces. the lighting analysis highlights of ecotect for double glazed window indicates four properties (Visual Transmittance, Solar heat gain coefficient, color, speculatrity). the product used for the double glazed window is Saint Gobain's Green Aura -- outer 6 mm with coating face 2+12mm air gap + inner 6 mm clear glass. While specifying this material in ecotect, what do we need to change? which property will define the outer coating face??

please can some one help me out on this?

i have attached snapshot of the element box that appears while choosing the material for thermal planes.

[Pennetier1]

Hi prerana_tuladhar, 

The only property you need to change is the Visible Transmittance (Vt) of your glazing.

Leave the SHGC to 1.0 for Daylighting analysis, otherwise it is going to be multiplied by the Vt and it will give you erroneous results (Do the opposite when running thermal calculations).  You need to have the Vt correct as Radiance will use that number to be translated into Visible Transmissivity and Ecotect will create the correct Glazing Material to be used by Radiance.

Set your Color Reflectivity to match your Visible Transmittance: first select the color white (Vt = 1.0), then enter the same Vt as your glazing.  This will set the RGB transmissivity correctly for Radiance; the Illuminance values will be correct, but if you run Luminance analysis, your colors might be off, unless you know the exact RGB of your glazing and can enter it. 

You do not need to worry about your outer coating; that is already taken into account by the Vt, SHGC and U-value of your glazing property.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,