glazing set up - absorptance
glazing set up - absorptance
When creating glazing, i note i can specify transmittance and internal and outside reflectance. How is the absorptance dealt with in IES as I cannot seem to detail this myself.
Re: glazing set up - absorptance
The absorptance is a derived parameter.
Reflectance + Absorptance + Transmittance = 1
thus: Absorptance = 1 - (Reflectance + Transmittance).
So: You don't have to specify the absorptance it's worked out for you.
Reflectance + Absorptance + Transmittance = 1
thus: Absorptance = 1 - (Reflectance + Transmittance).
So: You don't have to specify the absorptance it's worked out for you.
Re: glazing set up - absorptance
Excellent. Many thanks. Now generally we get given only the overall reflectance data. I assume this is the actual outside reflectance they provide. Is this assumption correct? So that when a manufacturer provides reflectance I apply it to the outside within the glazing tool.
Now ive written this, i now think that the reflectance data given will apply to the face that has the solar coating. On a DG window the solar coating is on face 2, ie the inner surface of the outer pane thus i guess i apply the reflectance data to that face. Ie the inner reflectance.
Now ive written this, i now think that the reflectance data given will apply to the face that has the solar coating. On a DG window the solar coating is on face 2, ie the inner surface of the outer pane thus i guess i apply the reflectance data to that face. Ie the inner reflectance.
Re: glazing set up - absorptance
Not sure if you have seen this but section 13.1 of the Apache Constructions Database User Guide has a 5-step process for matching glazing data provided by manufacturers.
Editing the outer pane of glass is usually the first place to start, i would recommend editing the transmittance value first. The overall SC is a product of the total unit. The internal & external reflectance values are always set to the default VE values, these values can be edited but really the transmittance value will have the greatest impact on the total SC. It is important that the long wave SC is much smaller than the short wave SC (less than 10%) Pilkington will give you these values you just to match them as close as possible within the VE. Editing glazing in the VE is a bit of trail & error & tweaking the input values.
Editing the outer pane of glass is usually the first place to start, i would recommend editing the transmittance value first. The overall SC is a product of the total unit. The internal & external reflectance values are always set to the default VE values, these values can be edited but really the transmittance value will have the greatest impact on the total SC. It is important that the long wave SC is much smaller than the short wave SC (less than 10%) Pilkington will give you these values you just to match them as close as possible within the VE. Editing glazing in the VE is a bit of trail & error & tweaking the input values.