Thermal insulation advice

[wesj]

Just found this great site,can anyone please help?
I am about to install a kitchen and bathroom in a new two story extension
including electrics (work will be notified to building control prior to state).The customer to go with 12 volt halogen downlights 8 in kitchen, 6 in bathroom and 3 in upstairs landing extension.I suggested for running cost and to future proof she use CFLs but she wants to go the 12 volt route
The downlight I intend to use are fire rated the type with steel can backs and IP rated over shower/bath
No problems in kitchen,180mm joists but I am concerned about upstairs landing and bathroom as the builder informs me he has to lay 279mm of insulation in loft. I intended to use 1.5 T&E to extend both lighting loops.Could you give thoughts and advice re the insulations effects on heat dissipation from lights and de rating the cables capacity.All advice/suggestions will be greatfully accepted
thanks in anticipation wes

 

[davy_owen_88]

Keep the cables out of the insulation and prevent the insulation covering the lights and you have nothing to worry about - simple

Clip the cables to the rafters along as much of the length as possible and cut out sections of insulation around the lights - you could also knock up a small plasterboard box and put that over the lights, but it's easier to just cut the insulation back.

 

[wesj]

Had to work this after noon sorry could thank you earlier.Your reply prompts another question an electrician friend says cables should no longer be clipped to rafters/joists as this is not good practice and against regs this to me sounds b-lls please comment .Thanks again
wes

 

[JohnD]

I wonder if he has in mind clipping to the tops of the timbers? In a loft, this is prone to damage as people clamber about on them in their great heavy boots.

 

[wesj]

No he says circuits should be re wireable/fishable this does not sound right
great site hope I,m not boring the pants or wasting your time

 

[JohnD]

don't understand that.

Fishing is what you do with a cable that passes through a cavity, e.g. behind dry lining.

Cables are supposed to be clipped at intervals (unless in conduit or ducts).

See if you can get him to draw a diagram of what he means.

 

[sausage1]

Hi Wes...

I think your friend is getting confused with parts of a circuit drop like feeding thru conduit run to a switch / sckts etc....

Drilling the joists to allow cable routing is ok (subject to build compliance on hole size / position etc) - see link but clipping is ok, but perhaps John D is right about boots etc!!

http://www.wycombe.gov.uk/uploads/d...ning/LocationofNotchesandHolesinJoistsA04.pdf