Window frame to glazing ratio change having on influence on the results

[David_S]

I am running senstitivity analysis on variety of input parameters in FlucsDL, to see the impact they have on the model. I have succesfully gone through the Tvis and window sizing, but got stuck on window frame (surely the ratio of glazing to frame has an impact on the amount of ligth getting into the building).

E.g. I've modified the window frame to glazing ratio settings from 10% to 50% (APcdb Project Constructions --> Glazed:External window --> Frame --> Percentage), but this has no impact on the output.

Things I have tried so far:
- quality settings in analysis parameters - even the high quality settings with all tickboxes ticked in the advanced quality settings did not make any difference (grid size tested up to: grid 1 = 0.1m; grid 2 = 0.1m; grid 3 = 0.2m).
- setting VLT to 0 in FlucsDL, to make sure the APcdb Construction (where the frame percentage is set) is referenced (as discussed at viewtopic.php?f=240&t=2646)

But no changes :[

Any idea what migth have go wrong??

[farahghanem]

I am not 100% sure about this, but I believe the window/frame ratio is only meant to be used to calculate the U-value for the glazing, and is not really used in daylighting.

[David_S]

Hi farahghanem,
Thank you for your comment and sorry for not responding earlier.
If this is true (i.e. the window/frame ratio is limited only for the U-value calc and is not picked the day lighting calc), this would represent a major limitation of the software. I guess the only workaround would be to change / redraw window sizes (modeIT) - but this can be a real nightmare on a big project (especially if rapid analysis of what-if scenarios is needed) ...

Hmm..

[farahghanem]

Hi david,

No worries. Try to confirm this with IES directly, and if it turns out to be as I said, then I am sure there is a shortcut command that can resize your windows as well, though I do not know what it is.

Hope this helps.

[David_S]

Hi farahghanem,
thank you for your thoughts on this, I will contact the IES support directly and post a conclusion if they come back to me.
All the best
David

[David_S]

I've got a reply from the IES support, and the conclusion is that:

"...the frame percentage specified in Constructions Database will only affect u-value/thermal calculations and is not used in the daylighting calculations within VE. Our official Training Sessions would recommend to have a different version of the model for doing the daylighting studies where your window sizes are drawn to only be the pane area.

Other options to modify an existing model without resizing windows would be to draw local shades over the windows to obstruct the frame area or adjust the transmittance properties of the glazing to reduce the amount of light allowed into the room and thus indirectly represent the non-glazed areas as a simple factor."

David

[farahghanem]

yes so like I thought, its only for u-value calc.

I would follow their advice on having a separate model for daylighting.