Cable in insulated ceiling void

[James Carmichael]

Hi,

SWMBO has deemed that we should stuff the floor joists to our kitchen ceiling with 100mm of *acoustic* insulation (so kitchen chit chat doesn't get overheard in the bedroom above) before we put new plasterboard on.

The joists are ~240mm deep and various lighting and socket cables are clipped to the joists and not in contact with the insulation. In some cases it makes logistical sense (given CH and water pipes) to push the insulation up to be in contact with the floorboards, in other voids it makes more sense to have the insulation at the bottom of the joists. It's either one or the other, so in all cases there is either a ~140mm void above it or below it.

The cables are either clipped above the insulation or below, but in either case will be in the ~140mm void left free by the insulation. At no point are they encased in it and at no point are they in contact with it on one side.

The ceiling voids are enclosed at each end so there is no through flow of air and the rooms above are carpeted including underlay. The ceiling will be standard 12.5mm plasterboard.

Various central heating pipes run in these voids. They never contact the cables and, where they share the same void (between two joists) as cables, have been insulated with 13mm thickness pipe insulation.

Am I right in thinking that this all constitutes REFERENCE METHOD B?

Thus, my 2.5mm radial socket circuits are rated at 21 amps (so, fine on the existing 20 amp RCBO) and my 10mm cooker radial is rated at 57 amps (so, fine on the existing 45 amp RCBO)?

Many thanks

James

 

[EFLImpudence]

Method B isn't actually given for flat twin & earth but for sheathed flexible cable is actually 23A and 52A respectively.

Even for t&e Method 100 - 21A & 45A, or 102 - 21A & 47A, where touching the thermal insulation on one side, would still be satisfactory.

 

[DetlefSchmitz]

Just a heads up. I did something similar (using Rockwool). It turns out that a surprising percentage of sound is transmitted through the joists themselves. Seems that you need alternate staggered joists (up/down) so that no individual joist is connect to both ceiling and floor. Of course, I don't know how much worse it would have been without the insulation. I did it because in those days they were giving subsidised Rockwool away virtually for free.

 

[James Carmichael]

Thanks both.

I have to say, having now spent the best part of a day scissoring some slightly springy joists and fitting the stuff, the 'chatter chatter', bang-the-cupboard door and rattle the cutlery tests tell me that the acoustic insulation has made less than bu66er all difference.

Still, I remind myself that the outcome here was not to make it quieter upstairs. It was to satisfy SWMBO that sound insulation is in place.

 

[DetlefSchmitz]

Absolutely.

 

[winston1]

Thanks both.

I have to say, having now spent the best part of a day scissoring some slightly springy joists and fitting the stuff, the 'chatter chatter', bang-the-cupboard door and rattle the cutlery tests tell me that the acoustic insulation has made less than bu66er all difference.

Still, I remind myself that the outcome here was not to make it quieter upstairs. It was to satisfy SWMBO that sound insulation is in place.

l don’t have a SWMBO, I have a wife and when she wants something stupid like that I put my foot down. Much better system.

 

[James Carmichael]

l don’t have a SWMBO, I have a wife and when she wants something stupid like that I put my foot down. Much better system.

It'll never catch on.

 

[John D v2.0]

l don’t have a SWMBO, I have a wife

Agree I don't see why people use this derogatory term, always grates when i see it

 

[James Carmichael]

Dear John,

You know nothing about me, my partner, our relationship, or our mutual humour.

But, still, you feel free to pass judgement if it makes you feel better. Keyboard warriors like you do, after all, make the world a better place.

Just rest assured that your sense of grating is all your own, a cross you will have to bear. It is not shared with my boyfriend, who - coincidentally - self identifies as SWMBO in our relationship.

Alternatively, get off your self important step, chill out, and enjoy Boxing Day.

It's up to you. Either way, I wish you well.

James.

 

[John D v2.0]

That's a very formal reply, however i wasn't passing judgement apart from on the words in front of me in isolation, as you correctly point out i don't know you at all, all i mentioned is i didn't see why people write it and it grates when i see it.
However in the spirit of inclusion the more examples of people different from myself the more understanding I'll be.
So it has indeed made me feel better that i understand more about other people so thanks for explaining and in the long term that will shift my perspectives on this in future.
Have a good boxing Day too

 

[James Carmichael]

Hi John,

Thanks for the reply.

You are right to call out 'SWMBO' generally; it's an artefact of misogyny, best left in the middle of the last century with mother-in-law jokes and anything related to Jim Davidson.

In my case, as I am sure you see, the use is consciously and intentionally ironic.

Anyway, hands shook - enjoy the rest of your day

James.

 

[Risteard]

It's called St. Stephen's Day here.

 

[EFLImpudence]

You are right to call out 'SWMBO' generally; it's an artefact of misogyny,

You were the one who used it.

 

[James Carmichael]

Indeed, I was. Hopefully the context in which I used it is clear to you and goes some way to explaining to you why I did so.

I fear that this thread is veering away from sensible discussion about electrical matters, so this is now the last post from me.

As before, thank you for your help and I wish you all a pleasant evening.

 

[winston1]

It's called St. Stephen's Day here.

St Steven's Day is the same date everywhere. But where you are, like the rest of the UK, it is referred to as Boxing Day.