Is LBT 1.4.0 able to model window constructions (EnergyPlus) defined with spectral glazing data (reflectance, transmittance)

Hi @chris,

Is this possible in LBT 1.4.0 ? Thanks!

No, it’s not supported right now but I have it as something that I eventually plan to implement:

I would say that it’s not too far of a priority after this one:

Thanks for considering this @chris !
I am willing to test this implementation if you want, I can run inter-software validations (e. g. compare LBT with DesignBuilder) for various glazing buildups.
This capability becomes very important when caclulating transmitted solar radiation through IGUs with selective coatings, which are typical nowadays. I have previously compared results between broadband and spectrally defined glasses, and broadband always underestimate transmitted solar significantly. This is why it would be very useful to be able to assign the properties (reflectance, transmittance) with the E+ Optical Data Type=Spectral, not SpectralAverage.

I have found similar differences when comparing the spectral values reported in LBNL WINDOW with what EnergyPlus actually assumes when using spectrally averaged glass properties.

I remember that the difference wasn’t too significant for most cases of double pane windows but I remember one case of a triple-pane assembly with lots of inter-reflections between glass panes where the SHGC was 0.20 using spectral data but only 0.17 when using averaged properties. So I know it makes a difference and you can rest assured that it is on our agenda.

Thanks! Here in Sweden TGUs are almost always the case, thus the need. Yes, mutliplying spectral transmittance of 2 different coatings (TGU: solar control + low-e) is less straightforward compared to 1 coating and a clear pane (DGU). As a mentioned before, I would gladly beta test this if you want.