My simple rule of the thumb to gauge the right brightness of your BH nesting room should pass the 2 feet test.
You simply stand about 2 feet apart and make sure you cannot see the other person's face.
Those birds tends to react negatively if your floor darkness is not proper.
One very common behavior is that they tend not to build their nests.
Yes they will stay inside your BH but will refuse to erect their nests.
My prediction is that they do not feel comfortable to start a family.
They will stay single or refuse to make love since those light are just too bright.
This will eventually result in lots of birds staying but the number of nests are too little.
Basically those light will come from two sources.
Main culprit will be the main entrance hole(s) and those air ventilation pipes.
If you look at these 2 pictures you can figure out how bright is this BH.
The first picture was taken from the right wall while the second was further back standing on the left wall.
This shows you how bright this BH is.
I wonder how come the BH consultant took no precaution to block them with some walls.
If he is a true consultant he should have done something.
Well maybe at that time he was still on a learning curve and have little idea about what brightness the nesting rooms should be.
The best solution is to erect at least two set of rooms to block those light.
My plan will be to erect something like this sketch:
All ventilation holes pipe extensions will be extended to about 2.5 feet long.
I am 100% sure those birds will love the new environment.
Darker and they will feel more comfortable.
The moment they feel comfortable those young couples will begin to mate and present the BH owner with nests.
This might be one of the many ideas that will help to increase the nests numbers immediately after revamp operation.