Loft insulation. Clipped direct or in free air?

[highspark]

As above really. All the rewires I have done recently have had mountains of this stuff installed. So is it bed to lay ontop of this stuff or continue to clip direct under if( which I have always done)

 

[truckster]

Lay on top. If its practical put in a clipping board (4x1) above the fluff to carry the long runs. keeps it neat and reduces the tripping hazard.

 

[Octopus]

Not sure that "laying it on top" is the best idea.

 

[highspark]

Well thanks for the words of wisdom Murdoch problem solved

 

[Guest55]

So long as the insulation is just on top and not completely surrounding the cable on all sides you dont need to de-rate the cable.
So i would lay cable under the insulation - will look neater and be less of a trip hazard.

 

[Guitarist]

Clipping boards along the walls and clip to horizontal trusses when possible then down nearby woodwork to sockets/switches. Easy to follow runs plus minimal exposure to nasty insulation.

Plus, if you take the oval conduit through the (now thick) insulation, the cables pop up where they can be seen. Also keeps them away from rodents.

 

[Guest55]

^^^ good idea , but an alot more work and cable , which is tough to cost in while keeping quote competitive.

 

[AP Electrical]

Slight off topic but I cant believe these gov grant insulation companies throwing 200mm of insulation on top of old cabling without a care in the world....

 

[ackbarthestar]

When wiring in lofts, cables should always be clipped direct against the joists and kept out of the way. Then you can fill the whole roof space with thermal insulation. Clipping direct against wood still means that the cables are not fully covered by thermal insulation since wood has a different thermal value.

 

[AP Electrical]

When wiring in lofts, cables should always be clipped direct against the joists and kept out of the way. Then you can fill the whole roof space with thermal insulation. Clipping direct against wood still means that the cables are not fully covered by thermal insulation since wood has a different thermal value.

True but what about heat dissipation.

 

[Top Cat]

If you wire lights in 1.5mm twe with a 6A mcb it should not mater either way.

 

[ackbarthestar]

True but what about heat dissipation.

Well, if you look at app4 table 4A2 you'll notice that a flat cable clipped direct to joists and covered with insulation greater than 100mm is given an installation method of 101 but if buried in insulation it is given a 103 method. now laying cables on top of thermal insulation will have the same derating factor as method 101 but without the good practice of mechanically protecting the cable.

If cables are laid across thermal insulation then I would suggest that that particular example is not used as part of an assessment.

 

[sedgy34]

the derating factor should be applied for ring circuits you may need to do a 4mm ring or radial

 

[Top Cat]

the derating factor should be applied for ring circuits you may need to do a 4mm ring or radial

Hi sedgy, you trying to bring that can of worms out again! Ha Ha agree with you though!:smilewinkgrin:

 

[Guest55]

the derating factor should be applied for ring circuits you may need to do a 4mm ring or radial

Ring main in a loft with no loft conversion ?
dont see those very often lol.