Covering electrical wiring for lighting circuits with loft insulation ?

[chris murphy]

"Hello All",


Could I get the Opinions of some of the Electrical Professionals Please regarding covering Electrical Wiring for Lighting Circuits with Loft Insulation - Here are some details regarding why I am asking - And although I THINK that I am correct in stating that this should NOT be done - the `Real World Practicalities` that I have been Reminded about:


I am advising a Relative about some Energy Efficiency Measures for their recently purchased Home - the most Obvious / Effective being to have the Loft Insulation Topped Up to 270mm thickness of Fibre Glass Loft Insulation.

This has raised the Question about the Lighting Wiring being Covered by the Loft Insulation - Which I think that I KNOW [?] should NOT be done - ?

I believe that I would have known many Years ago that this should NOT be done because of the possible Overheating of the Wiring - But I was `Reminded` by a representative from the Company who will be Installing the Loft Insulation that in almost ALL Lofts the Lighting Wiring CANNOT be lifted up to accommodate the Loft Insulation underneath.

He told Me that IF I was Correct in stating that the Wiring should NOT be covered EVERY Home that they Insulated would have to be Rewired for the Lighting Circuits - To Allow enough `Slack` in the Wiring to Install the Insulation underneath - Which obviously is NEVER done ! - And He stated that He would NOT want the Insulation Operatives to be `Pulling Cables About` in any case - Because of possible `Loose Wires`.

I have looked Online about Installation Methods for Loft Insulation and did find the comment about NOT Insulating over Electrical Wiring - BUT - As the Insulation Company representative stated this is NEVER adhered to by them or any other Loft Insulation Company that He has worked for.

And that this `Requirement` would STOP People from having their Homes Insulated because VER FEW People would be prepared to have an Electrician Rewire the Lighting Circuits to accommodate the Loft Insulation - ALSO - a very large percentage of the Company`s work is carried out under Grants for Home Energy Efficiency and these Homes would NOT be Insulated IF the Electrical Wiring had to be Redone - Thousands of Properties !


Obviously I realise [If this is correct ?] that with the use of `Low Wattage` / High Efficiency Lightbulbs [Lamps] there is not so much `Draw` through the Lighting Cables - and I assume that this means there is much less possibility of a Overheat Situation - ?? - But I was told that NOT Covering the Electrical Cables with Loft Insulation has NEVER been adhered to - Regardless of the Wattage Lightbulbs that were in use [NEVER even considered].

He / the Insulation Operatives were aware of the need for `Boxes` to enclose Recessed Lights prior to Loft Insulation being fitted.


I was told by the Insulation Company Representative that He could not remember this `Issue` EVER being brought to His attention and that He has worked for 3 Insulation Companies who have probably Insulated `Hundreds of Thousands` of Homes between them !

I would really appreciate the Professional Opinion of some Members - And I would ask Are the Electrical Cables in YOUR Lofts covered by Loft Insulation ?


"Sorry" to have written such a long Post about this - But I wanted to explain the situation correctly.


Chris

 

[SimpleSimon]

Alot of us on here will have theur own opinions on this topic.
Personally, lighting circuits should be fixed to the loft beams and not floating around.
if downlighters are installed a sufficient space should be cleared around each one so as no insulation could set alight or cause fire.
in regards to wiring, a sufficient assessment should be made on each individual household with the following.
-the load on the circuits.
- the thickness of insulation
- are there any other circuits ti group the cables with.
-Current quality of the cables.
all these factors an electrician will take in regard to suitably 'derate' the cable and make sure that its still efficient to carry the load of the upstairs circuit.
in cases of 270mm you may have to upgrade the cable to a larger size to accomodate a better cabke carrying capacity but i doubt it.

Sent from my GT-I9100 using Tapatalk

 

[chris murphy]

"Hello SimpleSimon",

Thanks for your Reply - I agree that IF this situation was being Investigated as a `One Off` / Onsite Decision there could be calculations done by an Electrician - BUT My main reason for raising the Question is that there is NO Consideration given to Covering Electrical Wiring by these Loft Insulation Companies.

`NEVER even considered` was the comment from the Insulation Company Representative !

From His comments and actually thinking about what I have seen in Lofts Myself - I would suggest that there are MILLIONS of Loft Insulations that are COVERING the Electrical Cables.

By the way - 270mm has been the `Recommended Depth` for Fibreglass / Rockwool Blanket Loft Insulation for quite some time now.

"Thanks for your Reply".

Chris

 

[SimpleSimon]

Chris your absolutely right. Unfortunately its one of things that come up where the mentality is "its not our trade so we wont bother"
Hopefully these home owners have since had a periodic inspection and the wires have been inspected and assessed. More time and money for the home owner but could prevent a fire and save a life.

Sent from my GT-I9100 using Tapatalk

 

[chris murphy]

"Hello SimpleSimon",

The thing is People do NOT have their Homes Inspected - And IF I am Guessing Correctly MILLIONS of Homes have their Lighting Circuit Wiring covered by Loft Insulation !

I am not writing about this because I think that this will be a `Revelation` to the Forum - It is just because what I was advising My Relative about caused Me to think about this - then to Ask the Insulation Company`s `Surveyor` [ Term used loosely] about it.

Then:

Because I am a Member on this GREAT Forum - Where there is obviously a WEALTH of Electrical Expertise and Knowledge - I wanted to get some `Feedback` about the `Real World` Installation of Loft Insulation - which is almost invariably OVER the Electrical Cables !

Chris

 

[Amp David]

For your lighting, providing its protected by a 6 amp CPD then theres not much to worry about.

Circuits like showers and socket circuits would or should be derated accordingly

 

[chris murphy]

"Hello Amp David",

Thanks for your Reply - Although I understand what You are saying about 6 Amp CPD [`Protection`] would there be still a chance of Overheating of the Lighting Circuits Wiring ?

I believe that My Relative has found that She HAS TO use some 100 Watt Incandescent Light Bulbs in Her Home - One of which is because a Low Energy Bulb interferes with one of Her Alarm PIRs.

And She also has Light Switch Timers Installed because She is away from Home frequently and uses these to give the Home a `Lived In` / Someone is In appearance - She / I have found that these can only be used with either `Good Quality` Low Energy Bulbs OR Incandescent Bulbs - As the Cheaper Low Energy Bulbs have a Constant Flicker due to the operation of the Light Switch Timers [Passing a small current ?].

She would be having these Incandescent 100 Watt Bulbs `On` for long periods of the Evening / Night in Winter - Any chance that the Loft Insulation would cause Overheating of the Cables ?

"Thanks for Your Help",


Chris

 

[Amp David]

Example.

1.5mm twin and earth installed above a plasterboard ceiling covered by more than 100mm of insulation, max current capacity of the cable is 13 amps and its protected by a 6 amp MCB.

A shower on the other hand wired in 6mm twin and earth, the cable has a current capacity of 27 amps and is probably protected by a 32 or 40 amp MCB. In this situation its an issue as OCPD is rated higher than the cable current carrying capacity.

 

[telectrix]

spot on there , amp. as long as the In of the MCB is < the derated ccc of the cable ..OK. with lighting, this doesn't usually cause a problem .6A is about 1300 watts or 13 x x100w lamps. it's showers , immersion heaters and socket circuits where problems arise, apart from the obvious one of heat dissipation from downlighters.

 

[chris murphy]

"Hello Amp David and telectrix",

Thank You both very much for your clear explanations.

I have worked in MANY Lofts - Installing Tanks and Pipework etc. and I have seen MANY cases of Electric Shower / Immersion Heater / Power Socket Wiring run in Roof Spaces - especially in Upper Floor Flats - where is was obviously much easier to do this than to take up Floor Coverings and then Floor Boards - Drilling Joists etc. - Run the Cables and then have to Refix the Floorboards and Floor Coverings.

I would imagine that there are MANY Properties where the Risk of the Cables Over Heating is REAL ! - Perhaps especially for Electrical Showers and Immersion Heaters [?].

As I asked in My Original Post - I wonder how many Electrical Professionals have Loft Insulation covering Their Electrical Wiring in the Loft / Roof Space ??
Those who did NOT carry out the Wiring themselves [The Vast Majority] - Have they given ANY thought to what I described in their own Home ??

I have been told by My Relatives Husband that the only Electrical Wiring in their Roof Space IS Lighting Wiring - He knows this because He asked the Electrician that I advised Him to get after the House Purchase to carry out a `Safety Inspection` [I know that some members don`t like this Term].

The Electrician did find some items that needed attention for Safety Purposes and also some New Sockets were required in better positions for the T.V.`s etc. - and I would ALWAYS advise a Home Purchaser to have an Electrical Inspection carried out straight away.

"Thank You" again for your comments and Technical Information.

Chris - Heating - Plumbing & Gas Installer