downlights

[SparkyTris]

Ive been thinking about fitting downlights in a problematic ceiling. the ceiling is plasterboard, secured to joists at 600mm centres. there is a 90mm void above the plasterboard, above which is a 100mm slab of closedcell polyurethane (kingspan type) insulation. Sitting on top of that is an underfloor heating system serving the first floor. but that's by the way. the problem is that there is only 90mm of void.

I can find a few "low-profile" downlights which will fit into the void. (obviously its the unseen profile I am talking about here!)

but, having fitted downlights before and having been frankly alarmed at the heat they generate behind themselves, I would like to fit fire rated ones (the ones that have intumescent stuff built in that (I presume) foams up and quenches any fires that start.

does anyone know of any good products around at the moment?

 

[Iggifer]

i'm not going to get into the finer points of installing downlighters, but have you considered LED lamps? Whilst they don't run cold, you can touch them while they're running, and have been running for hours, you could never do that with a traditional halogen lamp

 

[riveralt]

Its unlikely that 90mm of void will be sufficient to fit even low profile downlighters. Minimum size I have seen is around 45mm and then the manufacturers require space of at least 100mm all around the unit.
Incidentally, the perceptions that LEDs run cold is just that a perception. You touch the big heatsink and you will soon now what I mean. They also have a minimum distance around the unit.
Since the room above is occupied you have to ensure that the downlights you fit are fire rated which will also add to the height.

The final, nail in the coffin, if you will excuse that, is the kingspan. I think they require at least 150/200mm cap between their insulation and any lights that are fitted.
In all honesty, you might be better off putting a single central ceiling rose light in the room instead.

 

[SparkyTris]

good idea. Ill investigate.

 

[ban-all-sheds]

but, having fitted downlights before and having been frankly alarmed at the heat they generate behind themselves, I would like to fit fire rated ones (the ones that have intumescent stuff built in that (I presume) foams up and quenches any fires that start.

Fire rated lights do not run any cooler than non-fire rated ones, nor are they more tolerant of running hot.

If installed without sufficient clearance they will not be any less likely to overheat, nor any less likely to cause the conductors supplying them to overheat.

The foam in them is triggered into expanding by the heat from a fire in the room below - surely you aren't expecting them to run that hot, are you?

 

[SparkyTris]

this intumescent stuff, is it supposed to quench a fire which may start in the light enclosure or is it supposed to plug the hole in a wall if a fire is burning in the room?
what would its effect be on an energised lamp if it "went off" and foamed up around the lamp?

the LED lamps, is the heat generated by a power supply built-in to the lamp? the LED's themselves presumably run fairly cool.?

My feeling is that downlights in such a small (and well insulated) void might be a hazard indeed.

riveralt, thanks for your helpful comments & information.

"ban-all-sheds", you would probably contribute most help and information if you could resist typing for a few days. Perhaps I could suggest that you apply to Mastermind, specialist subject The Bleeding Obvious. But thanks for your enthusiasm, all the same.

 

[Iggifer]

Dont get me wrong, I'm not saying LEDs run 'cool' just 'cooler'. The Phillips ones are pretty good, I have grabbed the heat sink, just to test it and I could hold onto it - you could never do this with a halogen.

Even if it's only 10c cooler, this could mean all the difference.

Not that I'm reccomending fitting them in such a small void

 

[333rocky333]

only ones i have seen have a thin black film and all it does in the event of fire is expand a little and block the ventilation holes in the rear of the fitting, to prevent passage of flames into the void above, i personally have never seen ones that expand and extinquish flames.

 

[riveralt]

this intumescent stuff, is it supposed to quench a fire which may start in the light enclosure or is it supposed to plug the hole in a wall if a fire is burning in the room?
what would its effect be on an energised lamp if it "went off" and foamed up around the lamp.

The idea behind fire rated downlights is to help comply with the Building Regulations in so far as they apply to England and Wales - where breaching the ceiling plasterboard fire barrier, as with downlights, could cause fire to spread from one room to the next. Not sure what the situation is in Scotland.
In most fire rated downlights the thin intumescent gasket sits between the metal rim of the downlight and the ceiling and in the case of fire in the room where fitted will expand and act as a fire barrier to the rooms above -it does not quench the fire.

 

[ban-all-sheds]

"ban-all-sheds", you would probably contribute most help and information if you could resist typing for a few days. Perhaps I could suggest that you apply to Mastermind, specialist subject The Bleeding Obvious. But thanks for your enthusiasm, all the same.

What I wrote was clearly not Bleeding Obvious to you:

having fitted downlights before and having been frankly alarmed at the heat they generate behind themselves, I would like to fit fire rated ones

You thought that fire rated ones would be good because of the heat they make, so I pointed out that fire rated ones won't solve the heat problem, aren't designed to solve the heat problem, but are designed to deal with fires, and STG you aren't worried about them causing a fire?