Electrics - how close can we lay insulation

[spiidey]

We need to lay insulation, in our attic and also in the void between our upper and lower floors.

There are numerous electric cables running through the void and also in the attic.

In terms of insulation, how do we determine what we can lay, where we can lay it, and what density we can lay, to ensure we don't overheat any electric cables?

Is there a general rule of thumb or is it, as I suspect, extremely complicated calculations that are needed to determine this?

 

[winston1]

Why do you want insulation in the void between floors? Assuming both floors are heated the insulation would do nothing.

 

[delmel]

Think he means cables running over the joists and maybe having down lighters.

Always better to keep electrics cooler, but insulation is required. Keep it away from the fittings as best as you can, you could always extend the height of the joists if you so desire and notch out the extended wood for cabling to remain in same place. I am guessing you may be considering boarding also?.
Definitely also keep away from any transformers you might have.

You do not insulated generally between floors of the same dwelling, unusual to consider this.

 

[RF Lighting]

It's been standard practice to insulate all floor voids on new builds fur years now.

Why would you want to waste expensive heat into an unused upstairs room just to get the downstairs room warm?

 

[spiidey]

It's been standard practice to insulate all floor voids on new builds fur years now.

Why would you want to waste expensive heat into an unused upstairs room just to get the downstairs room warm?

Yes, this is my understanding also; however the house was repossessed and looks like the previous owner removed all the insulation between floors and the bank failed to put it back in (and we didn’t notice it at the time!).

So back to how much space to leave around electrics, I’m still unclear on this. Is there a standard calculation? i.e. if I have a mains cable running from the fuse box to a number of double plug sockets the other side of the house, how much space around the cable do I need to leave without insulation?

 

[ban-all-sheds]

It's been standard practice to insulate all floor voids on new builds fur years now.

Why would you want to waste expensive heat into an unused upstairs room just to get the downstairs room warm?

How many new-builds are so expansive that there are any unused rooms upstairs in the first place?

the house was repossessed and looks like the previous owner removed all the insulation between floors and the bank failed to put it back in (and we didn’t notice it at the time!).

It wasn't the banks responsibility to do that. Even if they had known, which they wouldn't.

And whilst some people do sabotage their house if it's been repossessed (I knew someone once who bought a repo and when he moved in he found he had no water - it had been turned off at the stopcock. He turned it on, and then found that not one tap had a washer in it. After he had sorted that out it wasn't very long before he found that the cold water tank in the loft had no float, and had had the overflow pipe blocked.), the sheer effort involved in lifting all the floorboards and removing the insulation makes me think it's far more likely that there was never any there in the first place.

So back to how much space to leave around electrics, I’m still unclear on this. Is there a standard calculation?

Probably, but the Wiring Regulations don't cover that, so someone with some proper design software will need to answer.

Unless we are all happy that Method 101 applies, not 102?

 

[jj4091]

It's been standard practice to insulate all floor voids on new builds fur years now.

Why would you want to waste expensive heat into an unused upstairs room just to get the downstairs room warm?

Really well that is very interesting, something I've never heard of. Thanks
As an after thought is that timber framed buildings only or ALL new builds, do you know if it is covered by a building reg.

 

[spiidey]

Back to the original query - when laying insulation, how much space do I need to leave around electric cables?

 

[JohnW2]

Back to the original query - when laying insulation, how much space do I need to leave around electric cables?

It's not really a question that can be answered in a general way. You do not need to have any space around the cables if the current-carrying capacity of the cable is adequate (in relation to the load and fuse/MCB protecting it) after it has been 'de-rated' (as specified in regulations) for being 'surrounded by insulation. .. so it really comes down to what you suggested/feared in your original message - that calculations (but not necessarily 'extremely complicated' ones) would be necessary to answer the question in relation to any specific cable.

Kind Regards, John

 

[flameport]

Is there a general rule of thumb

Ideally put cables on top of any insulation - this will not affect the cable or it's capacity.

If not possible, then cables for lighting circuits with 5A or 6A fuses/circuit breakers can be completely covered or surrounded with insulation, as the cable is already massively overrated.

For other cables such as those for sockets, showers etc. it depends on the circuit load, cable size, etc.