Hi

I'm thinking of installing some in the upstairs bathroom; which is
plasterboard with a thick layer of Rockwool on top.

I know from experience how much heat is chucked out from the
downlighters fitted in my kitched ceiling. So what's the correct
procedure for an upstairs ceiling? I'm sure there would be a fire
risk if I just left the layer of insulation untouched; yet to cut a
large circular hole in it around the light fitting would I'm sure be
very wasteful of heat when the lights are off.

I'm envisaging maybe I need to nail a plasterboard 'bridge' spanning
the joists adjacent to each light, and then running the Rockwool over
that, thereby leaving an airgap above the fitting. Is that
appropriate /OTT /inadequate?

Thanks
David