under or behind? – if behind does the glow object have a composite tag to not cast shadows
The area light is underneath the the glow/luminance object so this object does allow shadow so the light doesnt pass up and through to the rest of the building.
what are the GI settings and does the scene have any AO (either in materials or the whole scene)?
Global Illumination (standard) is set at 100% with 300 stocastic samples min res 20 max 200
Ambiant Occlusion is applied to scene Ray length 0-100mm, dispersion 100, samples 10-128 and 0% contrast
–bry
Bry