Low Energy downlights in reduced height cavity

[DJM]

OK, I know you guys hate downlights, but bear with me.

As a reult of dry rot and woodworm, I have had to rip a ceiling down and SWMBO has requested more light in th room. Want to keep the centre light, but as teh room ahs a sloped roof on one side I though a couple of recessed downlights will add just enough extra light in that are without restricting the ceiling height. And if I am going to put them in might as well make them low energy.

Now here's the rub, the sloped roof has only 4" beams and I will be putting 50mm of celotex between them, so I need short depth downlighter which is OK with celotex.

I have seen these http://www.qvsdirect.com/Elco-Low-E...Downlight-C-w-Lamp-Satin-Chrome-pr-23524.html
which seem to be shallow wnough, but what abput the insulation?

Anybody got any recommendations?

 

[ColJack]

the celotex will be in contact with the plasterboard surely.. so there IS no gap..
you don't push it up tight to the battons, you fit it flush with the underside of the rafters..

best bet is to copy the model number from that site and google elco lighting and try their website for tech specs and clearances.. ( we can't do it all for you.. )

 

[flameport]

4" beams and I will be putting 50mm of celotex between them

Lighting aside, only 50mm of insulation in a roof seems rather thin?

 

[1john]

couldn't you have two equally spaced pendants instead?

 

[DJM]

the celotex will be in contact with the plasterboard surely.. so there IS no gap..
you don't push it up tight to the battons, you fit it flush with the underside of the rafters..

I'm not sure what you mean here. I was asking if it was ok to drill a hole in the platewrsboard and celotex and fit, or if the hole in the celotex needed to be much larger to leave a gap between it and the fitting. I know the celotex will be in contact wiht the plasterboard.

the best bet is to copy the model number from that site and google elco lighting and try their website for tech specs and clearances.. ( we can't do it all for you.. )

I have already looked at their website, but it is not obvious (at least to me) whether it is suitable for use near insulation. I had hoped the experts here would have come across this issue and perhaps advise how close insulation such as celotex can be placed to light fittings such as this.

Flameport, yes 50mm is thin, but it is celotex so equivilent of 100mm, and it's 50/100mm more than before so an improvement. Unfortunately the rafters are only 100mm and as it's a cold roof space I need to leave at least 50mm air gap, so it's the best I can do.

1john, I could, but it wont reall y help as the low light is under the sloped roof and a pendant is just not suitable there.

I have also seen that Magaman do the Planes range http://www.megamanuk.com/megaman-products/luminaires/downlights/planex.php?pid=703222 but again no specifics wrt insulation

 

[ColJack]

it was the

so I need short depth downlighter which is OK with celotex

that trew me.. I thought you meant that you needed a fitting that would fit in the 2 inch gap left if you pushed the celotex to the top of the rafter..

 

[Steve]

Why downlights? You will always have problems with downlights in sloped ceilings. A couple of surface mounted swivel spots would be a better choice.

 

[electronicsuk]

The fittings you link to look like they use a GX53 lamp. If that's the case, there's no worry that anybody could ever replace the lamp with a halogen equivalent that would put out more heat. Those CFLs are pretty cool running, and the reality is that you're very unlikely to have a problem with heat dissipation. However, this may not necessarily be the opinion of the manufacturer, so it's your call.

 

[DJM]

The fittings you link to look like they use a GX53 lamp. If that's the case, there's no worry that anybody could ever replace the lamp with a halogen equivalent that would put out more heat. Those CFLs are pretty cool running, and the reality is that you're very unlikely to have a problem with heat dissipation. However, this may not necessarily be the opinion of the manufacturer, so it's your call.

Thanks for the feedback. The fact that those fittings use GX53 was one of the key choices as they run cool and nobody can fit halogens is one main reason for suggesting them.
As the fittings will be open to free air at the back, if I leave a 25 mm gap around the edges I can't see why there would be a problem. I have asked Megaman for their views on the planex fitting and well see what they say, assuming they reply.

The other obvious dissadvantage is that I have to try and solve the vapour barrier issue.

Steve, - surface mounted spots will just end up being knocked all the time

 

[mointainwalker]

50 mm of Celotex ( R 2) is equivalent to 80 mm of fibrewool insulation,
( R2 ) not 100 mm+ as you suggest.

Celotex is impermeable to vapour so once you have your safe distance from lamp, cutting accurately and also taping with aluminium tape to beams should take care of your vb issue if I have understood your proposal correctly.

 

[ColJack]

it may be impermeable, but cutting a bloody great hole out of it to fit the downlighter into will mess that up won't it...

you could always use foam backed board as well as the foam between the rafters.. give you some additional insulation.?

 

[mointainwalker]

@ColJack

That's why I added "..if I have understood your proposal correctly."

I didn't pick up anywhere how much lamp would be behind the pb and once I had read that the OP was talking about leaving a 25 mm gap between lamp and Celotex, then I didn't think he was still talking about drilling a hole in it. Hence my reply

By the way how did that flat re-build ( or new kitchen ? ) go that you mentioned some considerable time ago ?

 

[DJM]

it may be impermeable, but cutting a bloody great hole out of it to fit the downlighter into will mess that up won't it...

you could always use foam backed board as well as the foam between the rafters.. give you some additional insulation.?

I was thinking of producing a foil backed plasterboard box foil taped to the plasterboard for the vapour barrier. It'll stick up into the 50 mm air gap a bit, but still leave plenty of air movevment.

I have thought of insulated platerboard, but thickness and cost are a factor

 

[electronicsuk]

Either that, or buy one of the pre-made fire/vapour barrier caps that are available from the likes of TLC, then caulk around the inside edge through the downlight hole (as I assume there will be no access from above).