Hi, recently I worked on similarly lit project and one thing I can tell - that lighting scenario sometimes can be a real pain in you know where :) Well from my recent experience or rather my recent mistakes, you can learn this:
- 1st portals should be done similar to this
- on the outside of the window\door facing the interior plus one portal plane should cover entire opening no need to add portals for each of the window's glass parts, sorry if I'm mistaken about what you did, but you wrote "Corona standard lights and Corona sky/sun with
some portals on the front door" so I made a suggestion you didn't set up those correctly and portals done that way (I mean multiple portals, especially if done on the interior side of the window) can produce some ugly-never-going-away noise or just do not speed up rendering at all - it depends on the situation
- 2nd try to make window glass one sided geometry with thin(no refraction) option ticked in its material - this is quite important, yet not just for speed or noise (well those too, but difference is not too big) but more (from my bad experience) to the power/brightness of reflections/refractions/specular coming from the hdri (probably corona sky as well but I have not tested this) and it will be quite difficult to balance lighting and reflections coming from the outside with those from the inside objects - I don't know if that's a bug or physically correct behavior (which I highly doubt) but this happened to me so better be safe than sorry :)
Hope that helps .