Insulation around a Velux?

[Ian H]

Should I use foam around the edge before I board it, fill it with rock wool or leave it for air to circulate?

The window is above a staircase, not in a room.

Thanks

 

[bobsuerita]

the new ones come with a expanding rubber strip that fills that void but we used to foam around window then add 25mm insulation to sides then board but looking you may get 50mm on there

 

[freddiemercurystwin]

That rebate is for the plasterboard to slot into so that will leave whatever gap is left to pack with mineral wool or something.

 

[Ian H]

I cut slips of Celotex and pushed them in tight around the frame. Thanks