Noise

[Rombout]

When the sun is away you need to check all glass and reflective items i believe.

[Benjamin76]

With the number of lights in the scene and lots of translucent materials in use (division panels, table lamp shrouds, etc.), I won't be surprised to see noise hard to clean up.

The Rhino Sun is another major contributor of fireflies.

[Bogdan]

Another example. This time on a very simple model. I tested with the glass object as polysurface and single surface. I assigned a thea material instead of rhino default material and I also changed HDRI maps. It is strange how the noise and fireflies are showing up on the curtain wall but not on the glass rail.

[Rombout]

What color is the interior? Did you also check physical sky, perhaps the other IBL also has hotspots?

[Bogdan]

I notice problems when the light from the sun hits materials which are slightly glossy (like the concrete I used) and when those materials with their shiny areas are reflected in the glass. While in some materials this noise is not that visible, on the glass it becomes disturbing.