Instead of hanging down from the ceiling like conventional fixtures can lights extend up into the attic so that the only part you see is the front edge of the.
Insulation around recessed ceiling lights.
How to insulate around can lights.
The recessed lights in my house are accessible from the attic but there s no insulation around them because it says on the fixtures that they need to vent the heat generated by incandescent bulbs.
This video from green homes america provides a good overview of the air leakage issue with recessed lights and shows an actual top hat installation.
A number of manufactured products are available to provide clearance for insulation around the fixture but you can also build a box using scraps of rigid insulation or drywall.