Wiring and loft insulation

[smaug]

We live in a house built in 1999. The loft has fibre glass insulation which I propose to increase to modern levels. I understand from other posts that it is safe to cover the spot light wiring (not the lamps themselves) with insulation.
I am using insulated loft board for an area for storage. The instructions recommend lifting the wiring above the boards and using conduit where PVC-sheathed cable comes into contact with the insulation.

Any views on whether this is action is essential or is the manufacturer being over cautious?

 

[PrenticeBoyofDerry]

If your lighting circuit is 1.00mm T&E on a 5A fuse or 6A MCB/RCBO, the cable will be okay in thermal insulation.
Avoid covering any downlights and transformers, leave at least 150m area around these pieces of equipment. If you can it could be worth fixing any transformers above the insulation and boarded area.
The any power circuit cables for sockets, showers, cookers, heaters etc...
need to ideally be raised above the insulation, as normally the current rating of the cable is much closer to the rating of the fuse/MCB/RCBO and the demand of the circuit. Putting cable in containment such as conduit and trunking, also reduces the current carry capacity of the cable. So those instruction supplied with the insulation board is not the best advice for power circuits. So that may need a little more thought! Lifting the the cables above the insulation would be a better recommendation, than running within conduit.

 

[ban-all-sheds]

I am using insulated loft board for an area for storage.

OOI, have you chosen a make?

The instructions recommend lifting the wiring above the boards and using conduit where PVC-sheathed cable comes into contact with the insulation.

Is the insulation expanded polystyrene?

This will damage cables (it leaches the plasticiser out of the PVC and the whole lot dissolves into a gooey mess)

AFAIK PUR/PIR doesn't have this problem.

As others have said, the light wiring will be fine, but watch the clearances around recessed lights. You might like to consider building sealed enclosures around then to stop warm moist air getting into the loft.

http://www.nhbc.co.uk/NHBCPublicati...ical/StandardsExtra/filedownload,16553,en.pdf

As you put the boards down mark the positions of transformers, lights, junction boxes etc.

 

[17thman]

it annoys me immensely that loft insulters dont care a jot about covering downlighters. surley they have to be aware of the regulations and dilligent in their installations

 

[EFLImpudence]

And all the wiring in wall cavities of older properties.

 

[smaug]

Many thanks particularly to PrenticeBoy and ban-all-sheds for their advice.

The wiring in the loft is for spot lights and bathroom extractor fans on the same circuit with 6amp MCB plus alarms (fire and security)

I was intending to build enclosures to hold back the existing insulation but will now attempt to add a top and seal them. I was going to use hardboard but I guess it should be fire resistant. Any suggestions?

The boards were bought from B&Q and have polystyrene insulation so I will now be careful to make sure no wiring can come into contact with them.

 

[PrenticeBoyofDerry]

You can but firehoods/covers for the lights they are not that cheap but will prevent the spread of fire. You could also use 12.5 plasterboards instead of a combustible material or fire rated plasterboards, the transformers will still need some ventilation though.
hoods/braces
Also if fitting covers/hoods over the top of fittings, make sure the cables are left well clear of the lamps as they too can become damaged by heat through contact or close proximity.

 

[smaug]

Has anyone any experience of using aico Loftcaps?

They say "Maintains sufficient air space around the fitting to allow continuous roof insulation to be laid directly over light fittings without overheating or damage to the lighting"

Presumably I could board over them.

Alternatively would plasterboard enclosures be as effective if their volume was equal to or greater than that of the Loftcap?

 

[PrenticeBoyofDerry]

Proprietary cover such as the Aico loftcaps, are compliant with Building Regs Approved Doc L1B.