Loft insulation, downlights and wiring

manic

I am just about to top up the insulation in my loft & have a few questions.

First, I've read that you should place the wires in the loft ontop of the insulation to prevent it getting hot. The problem is that the electrician has drilled through the joists and fed the wires through. What can I do without having to rewire the lights.

Second, I have downlights in 2 rooms. I have read a lot of conflicting information about insulating over them. Loft caps are £10 each. Boxing around with plasterboard will take a long time. What are your thoughts.

Finally, I'm going to board a section over the rooms without downlights. I was looking at using knauf space board with chipboard on the top. They say 2 layers of space board are required. Would one layer of these be better http://www.diy.com/? Or is there a cheaper alternative?

jc808

what sort of downlights?

(halogen, cfl, led?)

manic

jc808 wrote: »

what sort of downlights?

(halogen, cfl, led?)

5 are Halogen 12v 35w GU5.3. They each have a transformer.
4 are old fittings that hold R80 reflector bulbs.

anotherbaldrick

Put a plastic flower pot over each downlighter.

anotherbaldrick

anotherbaldrick wrote: »

Put a plastic flower pot over each downlighter.

Upside down of course.

anotherbaldrick

anotherbaldrick wrote: »

Upside down of course.

That's the plant pot upside down , not you.

Gloomendoom

If the op used a clay flowerpot it would give a better fire rating. He could feed the wire down through the drain hole.

Swipe

I live in a bungalow and put all my loft installation over my mains and lighting cabling for the same reason as the OP i.e. the joists were drilled and the cabled threaded through. It's been like this for 3 years now with no problems. I just keep my eye on the loads I'm drawing on my energy monitor and make sure I don't draw more than 3 KW over longer periods of time. Most heavy usage tends to occur when it's freezing in the loft anyway. I just made a channel in the insulation so the cable for the separate circuit for my immersion heater can breathe as that is the only cable that gets slightly warm after an hour. I wouldn't have any concern about lighting cables unless you have lots of those halogen type bulbs that draw lots of power. Apart from re-wiring there's not a lot you can do. I'd also agree on the ceramic plant pots over the plastic ones.

Dave_Buchan

Hi,

Your wires are perfectly fine installed in thermal insulation, in a perfect world they would all be installed in a free air position but all the thermal insulation does is lower the cables current carrying capacity so in most general household situations covering them is fine.

With regard to your downlights, they're probably one of the most common causes of electrical fires in the UK, through poor installation practice.

If you're purchasing new downlights if you opt for a fire rated type you will be able to lie your thermal insulation straight over the top of them, if not you'll have to cover a standard type downlight with either fire guards or fire hoods.

I can't post the link to a quick reference guide about downlighters, installation and fire safety, as i am deemed a spammer but if you go to the electrical safety council website you will find the downloadable pdf. file there.



Hope this helps,

Cheers,

Dave

BoxerfanUK

manic wrote: »

Finally, I'm going to board a section over the rooms without downlights. I was looking at using knauf space board with chipboard on the top. They say 2 layers of space board are required. Would one layer of these be better http://www.diy.com/? Or is there a cheaper alternative?

In the centre (usable) space of my loft I already had 100mm of insulation between the loft floor joists, then put down 18 mm T&G chipboard loft panels on top (screwed down into the joists) then put one layer of thick space board type stuff over that, and then another layer of 18mm T&G loft panels over that (screwed down again). Rest of loft I put 200mm layer on top of the existing 100mm layer, so now exceeds the minumum required thickness in those areas.

I did toy with the stuff in your link but wasn't keen on the idea of the foam resting directly on the joists particularly where they overhang a joist centre. I also wanted something that would be permanent and immovable. Without screwing down the panels you'll be surprised how much they can move about.

Putting down two lots of the foam board would make screwing down difficult due to the thickness, but as I had two layers of loft panels sandwiching foam board the top board screwed down through the foam and into the bottom board this was done quite easily. This made a nice permanant fixing, but can be undone if required as they were screwed in.

Has made a big difference to heat retention in my house.