FYI, I had an estimate for adding cellulose insulation to the attic from a contractor through our energy companies. They indicated that for our ranch house all pot lights needed to have a dry wall box built for each one and all exhaust fans needed to be vented through the roof. Also, need to be careful not to fill soffits and avoid wind through the soffits blowing the insulation.
I'm a long time electrician, and builder. You have run into an interesting situation with your recessed lighting, based on dealing with your "energy company" which I'm guessing means your local utility. Many newer cans are both IC rated for direct contact with any insulation, AND labeled as airtight.
While discussing this with an installer for a large insulation/weather sealing contractor, I learned that this doesn't matter to them, and company policy demands a needless, energy wasting drywall fire stop box surrounding any existing recessed fixture. IMHO, it's just a CYA plan to protect the company, and prevent semi-skilled workers from creating a fire hazard. These same clowns also caulk with $1 a tube latex caulk that is totally worthless, has zero elasticity, and fails to adhere to many common materials. They do lots of sealing with silver foil duct tape, which falls off of many surfaces in short order. They are only required to reach 80% coverage when blowing insulation in existing walls, as checked with a thermal camera, before the utility signs off on the job. The worker also admitted to me that much of the blower door testing they do ranges from sketchy, to flat out faked. This BTW, is a nation wide firm that does work for utilities.
I'm no fan of the drywall boxes in this application, it seems like a foolish way to create a big empty void in the insulation. I would rated confirm it they are IC rated, which typically is a label or stamping that's clearly visible when the trim is removed, or replace them with airtight IC units. The other comments about fan venting and soffit ventilation are correct.
