Here is an example of what I see regularly in attics when improvements have been made to upgrade electrical or to add duct work. This photo show the attic side of a can light. Do you notice what is missing? I know you can't see that the electrician did not seal the space between the metal can and the drywall - which would help control infiltration thru the ceiling, but did you notice that there is no attic insulation surrounding this metal can. The electrician did his job of installing the new can light - but there was no follow up to reinstall the attic insulation that was pulled back for the upgrade.