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CRITICAL UPDATE - Glazing Materials for Lighting v4+

Message 1 of 15
5417 Views, 14 Replies

CRITICAL UPDATE - Glazing Materials for Lighting v4+

Insight Lighting versions prior to v4 use the old Rendering engine, which interprets Glazing properties differently than the modern Rendering engine used with Insight Lighting v4+.  When upgrading to Insight Lighting v4+, Glazing materials Appearance properties must be updated to have the desired Visual Transmittance (%VT) interpreted by the new engine.


Upgrade to the new Insight Addin is highly recommended.  It is ~100x faster, Glazing materials are much easier to use, and all materials are more accurate.


Please review the following AKN article:

Glazing Materials changes for Insight Lighting v4 and later versions


**Update Revit 2019 and 2020 to the latest patch to fix a bug in the 'new' glazing VT value in the Appearance UI.


Review this post for tips on managing Appearance assets:


**Adjusting 'old' Glazing materials for Lighting v4+ (new Rendering engine):  

The Glazing Visual Transmittance calculation has been significantly simplified, while adding some additional capabilities.  RGB and VT have a simple linear relationship, and thickness of the modeled glass element no longer needs to be considered, so a material can be applied to any model element, and it will yield the same visual transmittance.

Protein Glazing.png



  • 'Color' RGB defines the Visual Transmission:
         VT% = RGB/255   (for example (127,127,127) would be 50% VT)
  • 'Color' RGB when R, G, and B are different define Visual Transmission with weighted RGB:
         VT% = (0.2126 R + 0.7152 G + 0.0722 B) / 255
  • 'Reflectance' affects performance somewhat but is only a concern when Reflectance % is close to 1- VT%.  Using a value from window specs, or the default 5-15% will yield accurate results.  In either case, this should be the Reflectance of the interior side of the glass.
  • 'Sheets of Glass' now impacts the Visual Transmittance and should almost never be changed from the default value of ‘2’.  The default value of ‘2’ will have yield standard VT%, as it assumes that a glazing unit is 2-sided.  The default value should only be changed in the very rare cases that the Revit element is non-standard, or the window family contains multiple modeled panes and the TV definition is for the entire assembly.

** Opaque Materials Reflectance has not changed, and is still simply RGB/255.


** New Glazing type (beta) is available in R19 and R20.

(Note: This glazing type currently has a bug that shows an incorrect value for Visible Transmittance in the editor.  We recommend avoiding this Glazing type for Lighting analysis work until Revit has been patched to fix this bug)

  • In R19 this 'new' Glazing Appearance Asset is under the 'Glazing' category of the Appearance Library, while the 'old' Glazing is under 'Glass' > 'Glazing'.
  • In R20 the old and new Glazing Appearance Assets are both in the 'Glazing' category.  'Old' Glazing will have a warning symbol in the corner of the Material icon.
  • The 'new' Glazing type has a different set of properties in the Appearance tab of the Material Browser for materials with the Asset applied.  As noted above, the value shown for Visible Transmittance is currently incorrect.  When this bug is patched, we will post full documentation for this Glazing type.Prism Glazing.png


Message 2 of 15
in reply to: scheerd

Hi Scheerd, 


Any timeline on when this patch will come out? It looks like I should maybe consider reverting to the old glazing materials with rgb values to finish off my project? 



Message 3 of 15
in reply to: SteveDFThorne

Hi steve.

I couldn't share any timeline, and release dates are not guaranteed in any case.  

Yes, I would suggest sticking to the 'old' glazing and opaque materials for now.


Message 4 of 15
in reply to: scheerd

Hey there.

It is said that the thickness is no longer needs to be considered, but what if there are several glass panes in the window family (3 panes for e.g.)?

Thank you.

Message 5 of 15
in reply to: scheerd

Patches are out a couple months ago for R19 and R20.  Update to the latest, and the new Glazing assets are good to go.


Message 6 of 15
in reply to: ortemk

If the window family has 3 actual modeled layers of glass, then each layer will influence the overall visible transmittance.

The usual confusion is between the 'modeled' glass and the IGU spec.  As Lighting uses what's actually in the Revit model, it's the modeled glass that matters, just like the real world.

The standard recommendation is to model the IGU (insulated Glass Unit, or multi-pane window) as a single layer/extrusion.  The reason is that most window manufacturers provide specs for the assembly and not for each layer of the assembly.  If you have a window family with separate extrusions for each layer in the IGU assembly, then each layer needs to be defined properly with the layer Visible Transmittance.  

The way it works is, for example, if there are two layers, each with 50% Visible Transmittance, then the IGU will have 0.5 x 0.5 or 0.25 VT.

With Lighting v4+, it's no longer necessary to use the thickness of each layer to determine the VT of the layer.  It's simply either RGB/255 for 'old' glazing, or whatever is shown in the Appearance tab UI for Visible Transmittance for 'new' glazing.


Message 7 of 15
in reply to: scheerd

Autodesk, please provide clarification on the V4+ glazing materials and confirm:

Old Glazing Materials

Updated Revit 2020.1 Glazing Material Using Insight

  • If we use the new glazing materials from the "Appearance Library/Glass/Glazing" folder, then we use the report VLT from that material
  • Should we modify the "Transmissive Color" to alter the reported VLT for any of the new glazing types?
    • Example:
      • We want to lower or raise the reported VLT to a different value.
Message 8 of 15
in reply to: Tyrone.Marshall

'Old' glazing materials are interpreted by the new V2 Rendering engine (Insight Lighting v4+) as VT = RGB/255.

'New' glazing materials have a VT as shown in the UI for the Appearance tab of the Materials Browser.  They do NOT follow the RGB/255 rule, so you need to use trial and error to get your desired VT.

Be SURE to get the latest Revit patch updates for R19 and R20 so the VT is correct in the Appearance UI for the 'new' glazing materials.

The best documentation of this is in the AKN article here:

Glazing Materials changes for Insight Lighting v4 and later versions

Better documentation to come.

...and apologies for the difficulties during this conversion period.  With 2 versions of the engine accessible and supported by 2 epics of the addin, it makes things more difficult than intended.  Once everyone is on Insight V4+ and the 'old' materials are abandoned for the 'new' materials, everything will be quite simple.  For now, we are trying to support multiple versions of materials, Rendering engine, and Insight Lighting.  All in all, if you update to the latest Insight addin and update your R19/R20+ models to all 'new' materials, things will get simpler from here on out.



Message 9 of 15
in reply to: scheerd

Thanks, David!


Message 10 of 15



I have one more question, do you have any guidance for how we consider the following document with the new Revit Cloud Engine and Insight 360


My only other concern is that the manual adjustment of the new materials to get the desired VLT calculation- I wish there can be a better way to not lose any of the specific adjustments you have all made with those new glazing materials regarding color and other considerations.

Thank you,

Message 11 of 15
in reply to: Tyrone.Marshall

That document is out of date for glazing Appearance definitions.

We are in the process of revising the documentation, but it's a long process, and many are still using old pre-v4 versions of the addin, so it's a bit of a long task for us.  The more recent posts, and particularly the AKN article override all previous documentation for v4+.

BTW, there is a new version 4.040 available on downloads page now with a bug fix for downloading results for sDA analysis runs.


Message 12 of 15
in reply to: scheerd

Hello David (@scheerd),


I am hoping to grab some of your knowledge as I am running into an issue in Revit 2020 and I am hoping you can lend your expertise in giving me some guidance on glazing.


With the new change to Insight v4, I’ve updated a model with the new glazing materials so the glazing appearance assets appears. I’ve run a test analysis with VLT values and am noticing some very disappointing results. When I compare these results with the results of an original analysis (which used the original materials where the yellow caution icon was noted but the appearance was edited to note the proper VLT), I’ve noted that the results are very different and the updated glazing materials seem to perform much worse. I’m concerned that the v4 Insight engine is not running properly. I was wondering if using the RGB value for glazing VLT (from the provided tables) and the original materials from the database using this new version are still acceptable and yield accurate results?


best regards


Tai L

Message 13 of 15


Thank you for all the discussion above about the new material settings. I completely understand that LTV and RGB for new sets of glazing materials. Just wondering that for Old material, the reflectance value should be set to 5-15%, but in new material, we should ser the RGB colour for reflectance. Could you please let me know what should I set to reflectance value to be something equivalent to 5-15%  in old material? Attached is one sample of new materials. Thank you very much. Glazing.PNG

Message 14 of 15
in reply to: scheerd

It is stated in the Critical Update post that 50% VT has an RGB value of 127, 127, 127. Per the Insight help provided at the link below it indicates that a single 1/4" pane of glass at a VT of 50% is 1, 1, 1, double paned is 28, 28, 28, triple 73, 73, 73 - nowhere near the 127.


Additionally the below table appears incorrect in that it states that the RGB is 'whiter' with more panes of a 1/4" double pane at 50% is 28, but the same for triple paned is 73. Typically visual transmittance of glazing goes down with more panes of glass.


Can someone please confirm that the below table is incorrect and provide the location of how I can determine the RGB value of my glazing based on my VT? 


Transparent Materials · Insight Lighting Analysis Help (



Message 15 of 15
in reply to: scheerd

oke thank you

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