Green Building Forum - Insulated back boxes

Insulated back boxes

sgt_woulds — Tue, 14 Nov 2023 12:51:18 +0000

Been having some awkward conversations with an Architect recently regarding our Internal Wall Insulation using directly rendered woodfibre boards onto solid brick walls

Given that our parent company is located in Germany, a lot of the information we provide is translated from the original German documents and then edited to suit the UK.

One thing that has slipped through on our internal wall insulation manual is the mention of insulated back boxes for electrical installation. Unfortunately, as far as I can find, there is no equivalent product available in the UK and we should have removed this.

Que an E-mail in ALL_CAPS from an angry architect who is 'DISGUSTED that we sell natural insulation without 'THINKING ABOUT THESE THINGS'.

Explaining gently that we are a woodfibre insulation manufacturer, not an electrical factor seems to be falling on deaf ears...!

My question is, how is this normally dealt with for IWI in the UK?

Does anyone know of a product similar to this:

https://www.kaiser-elektro.de/en_DE/products/electrical-installation/flush-mounting/installation-systems-for-insulated-interior-walls/106/interior-insulation-box-for-insulation-thicknesses-30-100-mm

Insulated back boxes

Mike1 — Tue, 14 Nov 2023 17:25:44 +0000

Normally by fitting plasterboard. Direct rendering is not something that I've done and I've not come across a product.

Options could be just to fix the box in a hollow in the board using an extra long screw (or three). Lengths of plastic pipe, cut to length & filled with foam could also be used as stand-offs, in conjunction with a long screw.

Better would be to 3D-print some custom plastic stand-off brackets. Or adapters to interface between the Kaiser stand-off and the UK back-box (presumably the EU back-box can be unclipped from the product you linked to).

It may also be possible - but probably more expensive - to switch to an electrical range that is compatible with the Kaiser box. Jung, for example, produce a range of British Standard power outlets that I'm pretty sure are compatible with standard European back boxes. No doubt there are others who do so too.

Insulated back boxes

Nick Parsons — Wed, 15 Nov 2023 08:45:39 +0000

I have not come across the product you link to, but this is a perennial issue for me. it used to upset me greatly when sparkies dug out 40mm of valuable WF insulation to sink sockets, even when we were using 100mm. Of course it is worse if customer is following cautious advice re interstitial condensation risk and already limiting insul'n depth to 60-80mm. I always try to get clients to use surface-mounted boxes, or to have all sockets on internal walls. I usually lose that argument!

OP, assuming you are a merchant, could you arrange direct import of said boxes? While I might not agree with the archo's MODE OF ADDRESS I sympathise since, as I said above, it is an issue which bothers me. I don't like buying really expensive insulation and then digging big holes in it!

Insulated back boxes

sgt_woulds — Wed, 15 Nov 2023 08:46:15 +0000

Good call on the Jung range, I'll check that out

But, as you say, it would be an expensive option - IWI is expensive enough as it is! With retrofit of IWI becoming more important to meet UK energy targets I'm surprised there isn't a UK version of this.

Or maybe I'm not, we always lag so far behind the continent...

Insulated back boxes

Nick Parsons — Wed, 15 Nov 2023 08:52:01 +0000

As I type I am sat next to a surface-mounted socket box on 100mm WF. It is fixed with 140mm screws!! Should be stainless for lower conductivity, but they are not.

(Really struggling to post again. Keeps telling me I am not signed in when I am)

Insulated back boxes

sgt_woulds — Wed, 15 Nov 2023 09:08:14 +0000

"OP, assuming you are a merchant, could you arrange direct import of said boxes?"

We manufacture and sell woodfibre insulation to distribution hubs, we are not merchants. To be honest, it's hard enough to UKCA our own product range, let alone a third-party product. Importing anything into the UK since Brexit is expensive and time-consuming enough to make bringing in accessories not worthwhile.

As I said to the architect, we can only specify the insulation. Would you expect Kingspan etc to sell electrical sockets? I can suggest various 'bodges', (alternative technical solutions ) but they add time and labour costs and require the electricians to agree to - and stick to - the method.

We all know that a lot of trades just want to bash it out, take the cheese and move on to the next customer.

Interstitial condensation is a real issue - we have both WUFI modelling and real-life experience to prove it. On the plus side, natural insulations will 'deal' with excess moisture better than plastic ones but we need a solution to stop it in the first place.

Insulated back boxes

Mike1 — Wed, 15 Nov 2023 10:43:20 +0000

Posted By: sgt_wouldsit's hard enough to UKCA our own product range, let alone a third-party product.

I guess you'll know, but until June 2025 you don't need UKCA approval, so not a problem just yet. Maybe the entire UKCA system will have been ditched by then, as it already has been for some market sectors, especially if there's a change of Government.

https://www.gov.uk/guidance/construction-products-regulation-in-great-britain

Posted By: sgt_wouldsI'm surprised there isn't a UK version of this. Or maybe I'm not, we always lag so far behind the continent...

Indeed.

Insulated back boxes

djh — Wed, 15 Nov 2023 11:16:54 +0000

My solution to a similar problem was to have no sockets or switches on outside walls, as Nick mentions. But that is quite difficult and I can understand why it is uncommon. Upstairs isn't too bad since we could fit floor-mounted sockets in a couple of corners, but downstairs we have an extension lead all along one wall in a bedroom (I suppose I could have fitted the cable in the skirting board?) , a complete false stud wall in the utility room to allow sockets, plumbing and cupboards on an external wall, and a large extra box lime-plastered into the corner of the living room containing a load of sockets for TV & hi-fi etc.

But that was all because of my obsession with airtightness and wanting no penetrations at all in the inner plaster on the outside walls. In theory I believe I could have fitted Instaabox or similar but I don't understand how the sockets are mechanically secured. In general on the outside I dug a hole in the render and straw, filled it with resin and pushed a rawlplug or similar into the resin and then screwed into that once the resin had gone off. That seems to have worked with no failures yet.

Insulated back boxes

revor — Wed, 15 Nov 2023 16:31:07 +0000

Posted By: djh(I suppose I could have fitted the cable in the skirting board?)

That would be against regs as it is not classed as safe zone. It could be done I think if it were in a metal conduit which itself was also earthed.

Insulated back boxes

djh — Wed, 15 Nov 2023 20:09:19 +0000

I knew there'd be a reason I didn't do it

Insulated back boxes

sgt_woulds — Thu, 16 Nov 2023 08:26:51 +0000

There is no reason you can't run in the skirting as long as extra precautions are taken. The prescribed zones (150mm from edges and tops of walls and horizontally between electrical outlets) just mean that you can run cables without needing extra protection.

For any cables outside these zones they need to be buried at least 50mm, have conduit or capping protection, or run with armoured cable and be properly earthed.

I do wonder about those plastic skirting boards with the built-in cable trays - I suppose it is counted as surface mounting

I have a very amusing picture of my kitchen refurb where none of these rules were applied. it looked like someone was playing noughts and crosses.

Best ever, was a job where I was removing the old town gas pipes. Hackingsawing through a pipe I received a lovely little wake-up call - one of the previous owners had thought it made a lovely cable shortcut to get power to their side extension...

Insulated back boxes

geuben — Thu, 16 Nov 2023 08:34:18 +0000

Could you use plastic backboxes designed for plasterboard? The lug clamp things won't work so you'd need to fix through the rear, through the insulation and into the solid wall with your insulated fixings.

You'll lose the depth of the backbox in insulation but you could offset that by removing a little extra depth of woodfibre and replacing with aerogel.

Insulated back boxes

sgt_woulds — Thu, 16 Nov 2023 08:43:18 +0000

"I guess you'll know, but until June 2025 you don't need UKCA approval, so not a problem just yet"

Yes and no. There just isn't enough capacity to get all the products certified, so if you want to be ready for 2025 you need to be starting the process now.

You'd think the easy option would be for them to simply agree that European approval = UKCA for existing products but, unfortunately - politics!

Insulated back boxes

sgt_woulds — Thu, 16 Nov 2023 08:51:50 +0000

Posted By: geubenCould you use plastic backboxes designed for plasterboard? The lug clamp things won't work so you'd need to fix through the rear, through the insulation and into the solid wall with your insulated fixings.

You'll lose the depth of the backbox in insulation but you could offset that by removing a little extra depth of woodfibre and replacing with aerogel.

I spoke to a builder friend yesterday, who is deeply involved with retrofit to PAS 2035.

He uses the Compac Foam or Bosig phonotherm 200.

For thinner IWI he chases this back into the wall for the back boxes to mount on – they will screw into the insulation without issue.

Where the cables enter the box, he seals the gaps with intumescent putty for airtightness and the same between the back boxes and the insulation.

So there are solutions, but fiddly and time-consuming compared to properly designed systems from the EU.

Having worked on plenty of building sites over the years I know that for your average workman fiddly means 'bodge it and get off site before anyone notices...'