What loft insulation to use for spotlights?

[M3Sid]

I've just had some halogen downlights fitted to upstairs bathroom. In the floor of the loft above, what can I use for insulation over the rear of the spotlights? No doubt normal loft insulation would be a fire hazard if in contact with hot spotlights. Thanks for any help.

 

[dingbat]

NO insulation. None... not a sausage. This is one of the great hidden benefits of downlighters that the DIY industry doesn't want you to know - when they're on they'll heat up your loft nicely and when they're off they'll let your bedroom/bathroom cool down a treat. (And should you decide to insulate them anyway you'll be a boon to the economy as you replace lamp after lamp. Or, if they're extra low voltage ones you'll be replacing transformers as well.)

 

[Lectrician]

Fibre glass loft insulation is fire proof!

 

[dingbat]

Fibre glass loft insulation is fire proof!

Yes. It's the downlighters that are the fire hazard!

 

[breezer]

i have seen a job that the ceiling void was stuffed full of fibre glassm transformers survived (just) but the cables didn't

 

[mrscalex]

I asked a similar question only 2 days ago and was told the following by a pro lighting engineer.

The loft insulation typically found in a modern house is fireproof. If it wasn't then you'd have a very frightening fireball risk on your hands.

The problem comes from keeping the light vented. There should be no insulation all around to an area as specified for that light, like eg 8" on mine.

Even then, I was told that the only likely risk was shortening the life of the bulb through everheating. I'm sure others may also point out the risk to overheating the cables.

 

[phhut]

I have spotlight eyeballs in my bathroom ceiling - R63 - and I have fibre glass insulation in the loft - BUT I have pulled it back from the lights leaving about a two foot circle. Been like that for about 5 years or more with no problem.

I did think about placing a large lagged 'box' over them, but - as said by dingbat - I decided it would help keep my pipes from freezing up so I left it as described. Had no burst pipes as yet.

On that insulation subject - to my mind it would be better to lag the roof rather than the floor of the loft (given adequate ventilation) - at least then the heat is retained within the house and although the loft may not be used except for storage, it would prevent burst pipes.

 

[dingbat]

On that insulation subject - to my mind it would be better to lag the roof rather than the floor of the loft (given adequate ventilation) - at least then the heat is retained within the house and although the loft may not be used except for storage, it would prevent burst pipes.

Traditionally you insulated the loft floor, except the bit underneath the header tank. That seemed to do the trick. These days there are fewer and fewer header tanks and correspondingly fewer loft pipe runs. By insulating the loft floor you allow a good airflow to the roof timbers - insulating between rafters you run the risk of trapping moisture where it can cause most damage.

Back to downlighters; I have, in the past year, replaced three sets of ELV downlighters due to the secondary side cable insulation melting and shorting out the transformers. In each case the lofts had had their insulation upgraded.

 

[M3Sid]

Cheers and thanks for all the advice, wasn't expecting so many replies.

I made sure that I used decent transformers and even then one per downlight. Yes, a bit redundant (and slightly dearer) but makes installation easier and should a transformer fail then only one light goes out instead of a group of them. Also, the transformers have a thermal cutout which might offer some protection.

I just needed to know about cleareances behind spotlights and take your point about cables running hot (surely not if you use the right ones?). Thanks again.

 

[dingbat]

I just needed to know about cleareances behind spotlights and take your point about cables running hot (surely not if you use the right ones?). Thanks again.

Leave at least six clear inches all round the perimeter of each light (in practice that means effectively removing all insulation between the joists where the lights are. Most lights also specify a minimum void depth of 150-200mm, so there's no chance of installing them under boarding in most lofts.

And as for cable, many transformers come pre-wired, but they are prewired with cable of the correct current-carrying capacity for the conditions specified in the instructions - that is, without insulation.

 

[ban-all-sheds]

insulating between rafters you run the risk of trapping moisture where it can cause most damage.

What about all the loft conversions?

 

[pipme]

Some friends had a large 'loft' conversion... professionally designed and built. (only mentioned that because someone did calculations and did not just wave a finger in the air .. then use up that spare kit lying about in his yard )
There are a significant number of low profile 'vent' stacks added to the roof, they caught my eye when visiting .. These air the gap between felt and internal walls, which I believe are not separate little compartments between rafters, but also vented one to another.
Bit of help from the West country.
http://www.westwiltshire.gov.uk/building_control/guidance/loftconversions.php#ventroof

Did someone post having used upended earthenware pots .. (large flower pots with hole in base) ... sitting over the lamp - in the loft - must have been clear of joists tho'
P

 

[ban-all-sheds]

Did someone post having used upended earthenware pots .. (large flower pots with hole in base) ... sitting over the lamp - in the loft - must have been clear of joists tho'
P

I too have seen that suggested. Utterly bonkers idea.

 

[maxwell10]

Clay plant pots placed over the lights in loft will keep the lights cool and insulation away from them,also I seem to remember reading about special covers that can be placed over lights that smother them if catching fire.

 

[securespark]

Have you got the arrangement you suggest in your house, Max?