Home Builder wrote:

Is there a way to identify circuits with bad insulation without visual
inspection?

Yes. The equipment you need is commonly called a Megger. It applies a high
voltage (usually under 500v -- NM cable insulation is good for up to 600v)
and measures very small leakage currents to ground. It takes some
experience to give you the best results, and isn't absolutely accurate. You
may be able to rent one, but I recommend having an electrician who knows
how to use it and interpret the readings test your wiring for you.

--
Best Regards
Anthony Straight
http://dotznize.com/electric

This posting is an opinion only. The reader must use his own judgment and
assume any risk for following or ignoring my advice.