Replacing insulation over lighting cans?

[dilalio]

Aurora Enlite fire rated gu10 fittings in dropped ceiling in bathroom. Had to cut holes in plasterboard above dropped ceiling to accommodate the taller cans of the Enlites - they now protrude into loft space by about 10-20mm but are still well below the top of the joists.
I can part the grotty original rockwool away from the fittings, would it then be OK to put the newer cross-laid rockwool back in position, across the joists and over the top of the cans?
I'm speculating there's enough air circulation in the void created by the dropped lid and the lamps are COB LEDs anyway!
Would this be permissible?

 

[ericmark]

You seem to have miss understood what the fire rating is. Fire rating is to replace the resistance against fire getting through the ceiling they are not to allow heat to escape in fact the reverse, it is there so in the event of a fire the fire takes as long getting through where the lamps are as where there are no lamps. If you cut a second hole in the ceiling for the cans as you call them to stick through then you need another can on top of the first to replace the fire retardant properties of the plaster board removed.

 

[Taylortwocities]

These are your best option https://www.tlc-direct.co.uk/Products/JC94020.html

 

[oldbutnotdead]

At that price I'd be down the motor factors for a sheet of 0.8mm steel and bend my own. £10 each? FFS

 

[dilalio]

Do I need to go that far with it?
Like I mentioned... Most of the fitting is in the air gap between the old and new ceiling!

 

[oldbutnotdead]

As far as thermal cooling is concerned you're probably OK. It is the fire resistance of the ceiling which you have compromised and need to restore. Cheapest method (assuming the loft isn't boarded out) will be plasterboard over the TOP of the joists where your lamps are and side pieces to fill the gap between top and bottom PB (if space isn't a concern then board up the sides of the 2 joists then cover the lot with pb). Then bury the whole shooting match with rockwool or whatever.

Do you have to do it? Legally yes you do, practically it is highly unlikely that you'll be found out (I'm assuming building control aren't involved). Should you do it- yes you should, it'll cost coppers and it'll protect you and your house if anything goes horribly wrong.

 

[dilalio]

You seem to have miss understood what the fire rating is. Fire rating is to replace the resistance against fire getting through the ceiling they are not to allow heat to escape in fact the reverse, it is there so in the event of a fire the fire takes as long getting through where the lamps are as where there are no lamps. If you cut a second hole in the ceiling for the cans as you call them to stick through then you need another can on top of the first to replace the fire retardant properties of the plaster board removed.

I have to disagree on this one... I do understand the properties of the fire rated fittings (we call them cans around here). The integrity of the fireproofing between the room below and the loft space above is retained by the fittings themselves. The second layer of "ceiling" was not added for fireproofing purposes, merely for aesthetics! It is no different to the downlights being fitted into the original ceiling!

 

[oldbutnotdead]

Arrr, I see what you're saying (and just had a Google at the fittings). Yes you're correct- as long as the false ceiling (including lamps) presents an appropriate resistance to the spread of fire then the original one above can be ignored. For your original question, it'd still be better to put something across the joists so the insulation can't drop onto the lamps (plasterboard if there's only insulation up there)

 

[dilalio]

Thank f**k for that!
You had me worrying then
And, yes, I concur on the barrier between the top of the can and the rockwool s**t. Like in TCCs photo above, however, my situation means they are much lower down & just poke through the upper ceiling. And plasterboard is a lot cheaper than those bloody products
Thanks to you both!

 

[oldbutnotdead]

Thinking on, you might be as well to make larger cutouts in the old ceiling (so the hot back end of the lamp isn't too near lath and plaster or whatever it is). 50mm clearance should do it

 

[dilalio]

They already are
I used a 4" hole saw and made three lunges for each fitting!

 

[oldbutnotdead]

Excellent use of the word 'lunge'