Only if the fixtures are Insulation Contact rated fixtures designed to be covered with insulation. Otherwise you should maintain 7.5cm (3 inches) of clearance around the fixtures and leave the top of the fixture uncovered to avoid potentially hazardous heat buildup within the fixture.
The only acceptable way to insulate older, Non-Insulation Contact pot lights is to use a recessed light cover, made of fire safe material or build a sealed box over them and then cover the sides and top of the box with insulation. Minimum box dimensions shall be either 35cm wide x 1.2m long x 30cm high (14″ W x 48″ L x 12″ H), or 53cm wide x 74cm long x 30cm high (21″ W x 29″ L x 12″ H).