Downlights-Vaulted Ceiling-Vapour Barrier

NovaGSi

Good afternoon,

I am fitting downlights into a vaulted ceiling (new build), I have a number of questions;

Info on the roof/ceiling:
- The roof construction is with 9x2 rafters at 400mm centres
- I'm using 80mm extratherm between the rafters and 25mm insulated PB across the rafters
- I have cut a section 400x300 in the insulation betweent the rafters were the downlighters will go.
- The 400x300 section of insulation has been pushed back 80mm into the roof space, this gives a space of 400x300x80 behind the downlighter.

1 - How can I maintain the vapour barrier?
Do I tape up the joints in the insulation, the 400x300x80 section?

2 - Will there be overheating issues with the downlighter?

3 - Do downlighters cause condensation?


Cheers,
Mick

NovaGSi

Good morning,

any ideas?

Cheers,
Mick

DOCARCH

Quick answer - don't use downlighters in this situation!

Reasons:
1 - by cutting a 400 x 300mm hole in your insulation your in effect negating the benefits of the insulation in the first place - insulation is only as good as its weakest link.
2 - there is a fire risk/significant risk of melting the roofing felt (this was confimred to me by a roofing felt supplier) in addittion I know of one fire in house caused by recessed downlighters.

I specifically outline to clients that they cannot use downlighters in vaulted ceilings (where the ceiling follows the roof) for the reasons above.

If a client does insist on using downlighters in this situataion, I tell them they must at least use 'fire socks' over the downlighters.

If you search, there are plenty of other (architectural) surface mounted fittings that can be used instead.

Poor Uncle Tom

OP what is wrong with low voltage downlighters surface mounted on rails?

NovaGSi

DOCARCH wrote: »

Quick answer - don't use downlighters in this situation!

This is a serious fire risk then:eek: I didn't think (at least I've asked the question) there would be that much heat generated.

Poor Uncle Tom wrote: »

OP what is wrong with low voltage downlighters surface mounted on rails?

The wife is the problem - she doesn't like surface mounted/rails - there is no choice, I can't have a potential fire hazard.

What about LEDs?

Or products like these?

Thanks for all the advice/help, Boards is a great service/source.

Cheers,
Mick

http://www.pegasusassociates.com/3inLoVICHousingPNLIC301.html

MicktheMan

OP, don't use downlighters, they ruin the airtightness of the house. As mentined above use surface mounted fittings.
I do heat loss surveys and find a lot of times that the major weaknesses in otherwise well built houses are downlighters.

NovaGSi

MicktheMan wrote: »

OP, don't use downlighters, they ruin the airtightness of the house. As mentined above use surface mounted fittings.
I do heat loss surveys and find a lot of times that the major weaknesses in otherwise well built houses are downlighters.

I've got downlighters in most rooms in the house - the wife went mad with them:(

I live in a bungalow and all the downligthers have no insulation above or around them, how can i solve this issue?
I need to reinstate the insulation, how can I do that safely?
I was also going to put a second cross layer of insulation in the attic.

Cheers,
Mick

DOCARCH

NovaGSi wrote: »

This is a serious fire risk then:eek: I didn't think (at least I've asked the question) there would be that much heat generated.



The wife is the problem - she doesn't like surface mounted/rails - there is no choice, I can't have a potential fire hazard.

What about LEDs?

Or products like these?

Definitely a solution - but recessed downlighters really need free space to let the heat dissapate. You might find with this that your changing bulbs frequently because they have blown due to overheating.

Recessed downlighters can operate at up to 400C! Some Councils in the UK have published advisories recommending strongly not using them due to the fire risk.

LEDs might be the answer but I don't know what sort of heat they give out?

De_man

i used a chandelier instead of spots in sunroom;
bathroom (vaulted ceiling again) 6 LEDs (spots appropriately rated for bathrooms) each separated by 3 feet using the fireboxes that were previously
described, (LEDs give off very little heat)

MicktheMan

NovaGSi wrote: »

The wife is the problem [URL="http://"][/URL]

So solve the problem!!!:D:D:D

NovaGSi

MicktheMan wrote: »

So solve the problem!!!:D:D:D

LoL,

It's hard to get a hitman these days, they're booked up for the 8-12 months. Check out the news, they're working very hard these days;)

Cheers,
Mick

MicktheMan

NovaGSi wrote: »

I've got downlighters in most rooms in the house - the wife went mad with them:(

I live in a bungalow and all the downligthers have no insulation above or around them, how can i solve this issue?
I need to reinstate the insulation, how can I do that safely?
I was also going to put a second cross layer of insulation in the attic.

Cheers,
Mick

You need to leave enough space around the fittings in the attic to allow the heat generated by the lights to dissipate. This can be done with an airtight box made from non combustable material and sealed to the ceiling in the attic ( I read somewhere that you can get temps of up to 400 C from such fittings!). I would suggest at least a foot in all directions for size. This then can be insulated.
On the other hand, use a low energy bulb and you wont have such a heat dissipation problem. Hope this helps.

NovaGSi

MicktheMan wrote: »

You need to leave enough space around the fittings in the attic to allow the heat generated by the lights to dissipate. This can be done with an airtight box made from non combustable material and sealed to the ceiling in the attic ( I read somewhere that you can get temps of up to 400 C from such fittings!). I would suggest at least a foot in all directions for size. This then can be insulated.
On the other hand, use a low energy bulb and you wont have such a heat dissipation problem. Hope this helps.

How about a plasterboard box sealed with intumescent (spelling?) mastic?

Cheers,
Mick

Sparky78

I saw someone suggest using something like a ceramic/clay flower pot before.

Poor Uncle Tom

OP consider the insulation in the vaulted ceiling like a duvet on your bed.

Would you get scissors and cut holes in your duvet?
Would you notice if there were holes in your duvet?
Would you require extra heating because of it?

Is it better to try to patch up the duvet or not to cut holes in it to start with.

Quack13

OK, so maybe this is a stupid question.

But I just wanted to resurrect an old thread here with a slightly different angle on it.

Our timber frame is frame is currently being erected and we are starting to look ahead at issues that will be arising down the line.

One of these is lighting types.
I understand the reasoning behind ot putting downlighters in the vaulted ceilings, upstairs ceilings due to it compromising the airtightness/insulation properties etc.

My question is, in this type of build I am assuming it is ok to put downlighters in ceilings of the ground floor rooms as this does not effect the overall airtight envelope.

Am I correct in saying this?

No6

If you must have downlighters consider a suspended ceiling dropped 150 to 200mm below the line of the insulated and airtight ceiling, batten out new layer of plasterboard , skim and cut as many holes as you like. Most downlighters will now be using CFl or LEDS (or should be) these do not run as hot and will reduce the fire risk considerably, although if the ordinary ones get too hot with insulation around them they usually just blow the bulbs. If that is too much trouble then use surface mounted light fittings.

soldsold

Is 150mm really needed for LED lights?

I would have thought about 50mm was enough? ie a normal service cavity with the airtight membrane behine it?