Fire Hazard????


Prominent Member
Oct 31, 2000
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Herne Bay, Kent
I have just finished installing three circuits of low voltage lighting in the ceiling of my lounge/cinema room. Before I put the floor back down I have intention of trying to reduce the noise by filling the cavity with as much fibeglass style loft insulation as possible.

My concern is with the heat generated by the lights, will this become a fire risk. If it does what precautions should I take or is there an alternative filling I can use that wont give the same result:confused:

Or am I worrying for nothing.:(
I'm pretty sure rockwool style insulation is fireproof.

12v downlights do produce lots of heat so allowing space for movement of air immediately above them is a good idea. I've got exactly the same set up in my cellar. There is a fist sized gap in the rock wool, made by a fist coincidently, around all the light fittings. The floor above gets warm, especially when the lights are left on accidently for over 12hrs, but I have NEVER smelt burning or experienced any other signs of combustion.
I'm using the mains equivalent, and those lights generate so much heat, that my temperature probe went off the scale!

I tested the lamps by putting them into a spare piece of plasterboard I had, then laid loft insulation directly on to the lamps underside as if it had been installed into the ceiling without any gaps. It was totaly enclosed with no room around it.

I switched it on, and with the probe in place, watched the temperature rise. The rockwool did darken after a few hours, but it's very fire resistant, so you should be fine in that respect.

The installation instructions said that it should be at least 5" away from anything combustable, so try to mount it away from wooden joists/beams, or line them with plasterboard.

My lamps are in a small false ceiling in the apex of my loft HC room, and even after also leaving them switxhed on for over 12 hours, I never smelt any burning etc.

I did fit a linked smoke alarm in the loft too, and it's linked to the one in the downstairs stair well. If one goes off, it will set the other one off, so you will know in advance if there is a fire going on. Very handy when watching a movie I think, or if the HC room goes up while you're asleep. :)


Thanks for the comments guys, I am a little more reassured.

The thing that got me thinking is that I just moved into a new house and this has low voltage downlights in the upstairs bathrooms which obviously come out in the loft and the fibreglass has a hole cut in it around the light.

It just makes me wonder why?
Probably just a precaution.

Rockwool is fire resistant, not fire proof, so ensuring it doesn't actualy come into contact with the lamp is just for extra safety.

I did the same with mine just to be on the safe side, and for peace of mind.

We had halogen downlighters in my previous flat and because they were poorly installed the bulbs fried the transformers which were too close in the cavity.
I would sacrifice some of your sound proofing for ventilation around the bulbs - it should also make changing the bulbs more pleasant - as you won't get covered in bits of fibreglass.
Hi John,

For your information ,I,m a Firefighter, and unfortunately have attended several incidents involving these type of lights and associated transformers.

I do not claim to be an expert on the fitting of the above, but from what I have seen, I would say the safest bet would be to leave the recommended space around them.

Hope this helps.

Kefmad Rich.
id be very careful about making it up as ypu go along.i can assure you rockwool does burn pretty nicely with a crisp yellow flame. it may scorch for a while and look ok but who knows if or when it will take. you would be mental to rely on self made diy experiments or guesswork. get a pro in and you may get burned a bit in the wallet but thats better than getting ur arse scorched or worse someone elses. 2 further ;points. if you must continue yourself install fire hoods to ur lighting and make sure that your insurance covers you in the case of change of use. for instance garage to home cinema conversion may not be covered without proper regs appliance and approval.i think its ok to diy to save a few quid but not when ur this far out of ur depth. fire aint nice....get a pro in and sleep better at night......
Only a five year old thread.....:confused:
5 years but what the heck :D Down lighters can be a big fire risk. Two possible solutions for you:

1. Fireproof hoods like;jsessionid=QP5ZFARAOK3GICSTHZOCFGA
These are a bit over kill as they maintain fire protection barriers for 30 and 60 mins. But they are designed for placing over down lighters.

2. You can use a teracotta plant pot :) these keep any insulation away from the heat and provide a nice hole to let heat out and let the cable in.

Latest building regs require LV downlights to be of the type with a fire resistant hood if installed in a ceiling with a habitable room above. - eg downstairs room with a bedroom above.

your problem wont be fire mate it will be the transformers getting too hot and eventually they will just stop working, most current electronic transformers have a trip in them for this but they will still break eventually, fire hoods do not prevent fire, they are to continue the fire integrity of the cieling beter off with fire rated fittings in my oppinion, if you are putting fibre glass in the floor space leave a gap of about 18" around the fitting and transformer to allow for allittle bit of air flow hope this helps
ched, fire hods are there to keep the ceiling fire rated, not to stop the lights cathing fire to building materials.

Lamp life and transformer life will be greaty reduced if cover in insulation.

Anyone who covers DL or only leaves a small gap is asking for trouble.

Have not of you actually bothered to look at the instructions? :rolleyes:
ched, fire hods are there to keep the ceiling fire rated, not to stop the lights cathing fire to building materials.

I did say that they are there to maintain the 30 or 60 min fire protection barrier and that they were a bit over kill. But they would do the job and protect the insulation.

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