You can buy airtight reflectors and foam seals for where they meet the drywall. You don’t have to replace the actual recessed fixture with an airtight fixture. You do need to make sure they are IC rated (insulation contact) or you have to build boxes around them in your attic to prevent insulation for touching the cans. Retrofit LED’s should eliminate that as a necessity since they don’t generate nearly as much heat but I would not trust that for sure.This is an educational thread on insulation and has answered a lot of questions for me and I'm sure others. I have those leaky can lights in our house around 16 of them and I put those retrofit LED lights in to reduce heat plus they last longer than bulbs but still, they have the air leaks. so , I'm building styrofoam boxes out of 4X8 sheets and I'm going to put them over every can light in the attic I can reach. Only reason I'm posting this is to see if someone else has the same problem and how they solved their coolant and heat loss.