Window frame input option

asked 2022-09-18 21:37:33 -0500

Keigo's avatar

updated 2022-09-18 21:49:44 -0500

Sorry for asking a beginner's question.

I think there are two main options to consider window frames:

  1. Calculate total U-value, SHGC, VT, etc. including frames with LBNL WINDOW Program
  2. Use WindowPrroperty:FrameAndDivider and input frame property separately from glass property

According to I/O Reference, WindowPrroperty:FrameAndDivider adds frames outside the window vertices.

image description

As a result, the total window area is different between Option 1 and Option 2. How does everyone address this issue? It suggests that we need to determine which Option will be used before modelling window geometry. If we want to change the input option in the middle of modelling, we need to change the window geometry as well. It's very inconvenient. Or is there any way in EnergyPlus to add frames inside the window vertices?

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Nice summary, @Keigo. This is my understanding as well : one must choose in advance one option vs the other, and then offset window geometry accordingly. Alternating between options would require re-adjusting geometry. As you suggest, having a (future) option of defining rough opening vertices (i.e. frame width offset internally) vs glazing vertices (i.e. frame width offset externally) would be nice. BTW, LBNL's Window program generates input for either option.

Denis Bourgeois's avatar Denis Bourgeois  ( 2022-09-19 06:10:49 -0500 )edit

Thank you for your comment. then, currently we can't add frames inside the window vertices... I really hope the future option.

Keigo's avatar Keigo  ( 2022-09-25 09:00:41 -0500 )edit

Correct @Keigo. One could write up a bespoke script offsetting subsurface vertices (back-and-forth, by the frame width) when opting w/w/o Frame and Dividers, to ensure constant WWRs. We did something similar for OpenStudio models. But it would definitely be preferable to have the option up front.

Denis Bourgeois's avatar Denis Bourgeois  ( 2022-09-25 14:32:09 -0500 )edit