Airtightness of multiple cable entry

[tanneja]

We have been working our way around the house addressing airtightness, and feel we are doing our best, where this is now a best efforts approach since we are already half way through first fix when really appreciating the detail involved.

 

We have already pulled data, alarm and audio cables through from the garage, via an uninsulated vented porch loft, to the main house.  So we have a single bore hold that carries 20-30 cables.  I can see on the internet airtightness products for cable pulls, but they are all intended to be in place before you pull a cable, where you then pierce the membrane as you pull each cable through.  What if any chance do I have of making a suitably airtight fix for this?

 

In addition, we have hot water pipes (plastic) making the same route via a parallel bore.  These will likely expand and contract with hot water, so to simply silicone around the entry to the wall feels risky.

 

Help!

 

 

[tanneja]

Hijacking my own thread, I also need to have a precise plan for the socket and switch back boxes in the timber extension, and the spot down lighters under the flat roof.  It feels like the sockets for other internal studs and the solid externally rendered (and internally parged) brick external walls shouldn't be too tricky to overcome.

 

For the external timber elements, as normal will have an AVCL layer just behind the plasterboard.  My builder is accommodating of my views but sceptical as to airtightness measures.  He says he would usually have the wires pulled to the general area, and just puncture the AVCL to get them through (the wiring has already been pulled, will be behind a final slim layer of PIR and the AVCL), not usually making a seal to the AVCL around the wires.  He then offers up the plaster board with a small cut out for the rough socket / light exit.  Then when done for all boards, get the lasers out and nicely micro manage the positions of the sockets and lights, then making the PB entry holes bigger to offer in the back box or light fittings (presumably causing more trauma to the already compromised AVCL), and wire up. 

 

This approach means I feel I would struggle for a retrospective airtightness, perhaps hoping for an inner backbox putty to attempt my airtightness, but the AVC wouldn't be bonded to the backbox housing in anyway, so would be PB achieved airtightness.  Are the expensive and seemingly generous sized Instabox (https://www.phstore.co.uk/instaabox) and Optime (https://www.phstore.co.uk/optime-downlight-housing) housings the go to option for maintaining your airtightness recesses and so allow the builder to do their usual?  Presumably the seemingly generous size of these units mean the builder can install these in the approx. position prior to the PB, then micromanage the penetration a bit as he planned with the laser, as long as he falls inside the generous boxes.  Seems like an expensive but logical plan. 

 

Or, can you be a bit more cavalier and bunch up the AVCL in the penetration areas to provide slack for it to protrude back into a PIR cutout cavity?  Then you would just need to grommet or tape the cable penetration through the AVCL.  That might not be simple to achieve, but the cost of the back housings for lights and sockets is quickly adding up (probably 10 sockets, and 10 downlights), unsure what is the best way on balance.

Edited January 25, 2021 by tanneja

[Onoff]

10 downlights? You'll hit the problem I did, a lovely vcl punctured to Hell with holes.

 

With hindsight I'd have counter battened the ceiling and use slimline LED fittings.

 

Initially I left cutouts in my PIR:

 

 

I cut and filled these voids with pir intending to simply lift out from above.

 

A vcl went over the top then moisture resistant plasterboard:

 

 

At this stage, a nice airtight ceiling detail, I should have counter battened and put another layer of mrpb on.

 

(Leave btw some (known) gaps in the battens to allow for cable push rods should you decide on more lights later).

 

 

I'd however foil taped the underside of the pir insert pieces and I  had to pull up the pir. That left the foil in place ?

 

 

So I made a template using the downlight hole as a reference and cut down through the foil and vcl.

 

 

 

I'm using Thermahoods, aka posh flower pots.

 

 

I'll end up with a detail like this. I've to seal the edge of the hood down, insulate (foam fill) around the whole lot and over the top. Then to airtight seal the cable entries from above as well as vermin proofing it all.

 

 

Sound complicated? Too right! All this could have been avoided! 

 

 

Edited January 25, 2021 by Onoff

[TonyT]

I would have counter battened as Onoff suggested.

the number of fixings from the batten into the VCL would be less than if screwing plasterboard to it.

slimine down lights are also available but these generally have a led driver elsewhere to locate.

 

 

https://www.cablejoints.co.uk/sub-product-details/cable-jacks/rise-rapid-cable-duct-seals

 

I’ve used this in areas where gas is present, it’s I suppose the quick version of a cable transit, where cables used to be individually passed through a penetration in a wall, surrounded by rubber block and squished to make a seal.

[tanneja]

4 hours ago, TonyT said:

https://www.cablejoints.co.uk/sub-product-details/cable-jacks/rise-rapid-cable-duct-seals

 

I’ve used this in areas where gas is present, it’s I suppose the quick version of a cable transit, where cables used to be individually passed through a penetration in a wall, surrounded by rubber block and squished to make a seal.

@TonyT that cable duct deal looks somewhat retrofittable to me, I offer my sincerest thanks for the assistance.

 

@Onoff I have admired your room AVCL pics for a while now from other threads, you aren't my builder's favourite person.  I can allow some room height loss with slim height LEDs, I just seem to read a lot on this site in the lighting section that GU10 is the way to go for best light effect and to ensure you can get bulbs in the future.  Are the slim LEDs up to the task?  I was following @MJNewton in his quest for best lighting and he ended up with GU10 LEDS.  Would anyone have any recommendations for slim downlights that I won't regret?  Can I avoid much if any cavity if I go for the slim LED spots and perhaps have a fire mat above (as seen on another thread)?

 

I will at least need an Onoff style fit for the two deep speakers I have in the flat roof section.  I won't have access from above as the roof membrane is already done.

Edited January 25, 2021 by tanneja

[Onoff]

2 minutes ago, tanneja said:

Are the slim LEDs up to the task? 

 

I don't actually like them myself, it's more a case of what I grew up on. Go through a Hell of a lot of slim ones at work but that might be just sheer numbers. I prefer "proper" downlights but I'd go with slim ones in future as long as they're easy enough to access and replace. The benefits outweigh anything else in this instance. The slim, flat panel ones do give a superior spread of light / beam angle generally.

 

3 minutes ago, tanneja said:

you aren't my builder's favourite person

 

Tell him back of the queue!

 

I like One Gel, again habit I guess:

 

https://www.tlc-direct.co.uk/Products/WKONEGEL.html

[Thorfun]

sorry for the hijack but I'm planning on running the VCL up in to the loft and on the inside of the insulation between the roof beams so downlights in the first floor ceiling will still be within the airtight layer. is this a valid solution to this problem? Also means that the storage space in the loft is within the insulated envelope of the house. Think I read this is a warm loft rather than a warm roof.

[tanneja]

1 hour ago, Thorfun said:

sorry for the hijack but I'm planning on running the VCL up in to the loft and on the inside of the insulation between the roof beams so downlights in the first floor ceiling will still be within the airtight layer. is this a valid solution to this problem? Also means that the storage space in the loft is within the insulated envelope of the house. Think I read this is a warm loft rather than a warm roof.

That would work given my laymans understanding.  My most problematic area is a cold flat roof ground floor extension.  Had to be a cold roof to various reasons.  Seems now the search is on for a slim profile, square housed, matt black, dimmable LED spot which needs minimal or no cavity behind it, is likely to be around in the long term for replacements, and doesn't cost a fortune.

 

@Onoff is there anyone on the board who you follow or know of who has admirable aesthetic standards and found LEDs they were pleased with?  Working my way through a labyrinth of lighting forum posts over the last 24 hours, and I am a slow reader 

[Onoff]

18 minutes ago, tanneja said:

That would work given my laymans understanding.  My most problematic area is a cold flat roof ground floor extension.  Had to be a cold roof to various reasons.  Seems now the search is on for a slim profile, square housed, matt black, dimmable LED spot which needs minimal or no cavity behind it, is likely to be around in the long term for replacements, and doesn't cost a fortune.

 

@Onoff is there anyone on the board who you follow or know of who has admirable aesthetic standards and found LEDs they were pleased with?  Working my way through a labyrinth of lighting forum posts over the last 24 hours, and I am a slow reader 

 

Why not just get some Aurora Enlites and get the bezels resprayed to whatever? Simples. They come in white, chrome, brushed etc. Not sure about matt black...gun metal maybe?

 

Oh hang on you want slim fit...don't know ref the slim ones.

Edited January 25, 2021 by Onoff

[tanneja]

What does anyone think of the instaaboxes?  I am concerned by their depth eating significantly into our insulation depth on the external walls.  https://www.phstore.co.uk/instaabox.  Is there a better way?

[TonyT]

I would be more inclined to take a metal box before fitting to the wall and wrap it with air admittance tape.

 

then fix the box to the wall and bring cables into box, then seal the 2 box fixings and 1 cable penetration.

 

Same outcome considerably cheaper.

[tanneja]

18 minutes ago, TonyT said:

I would be more inclined to take a metal box before fitting to the wall and wrap it with air admittance tape.

 

then fix the box to the wall and bring cables into box, then seal the 2 box fixings and 1 cable penetration.

 

Same outcome considerably cheaper.

Thanks Tony, would that mean PB at the end after having done that presumably?  And is the ideal tape Tescon Vana?

Edited January 26, 2021 by tanneja

[TonyT]

Sorry not following.... what’s pb?

 

I used pro Clima uni tape

[tanneja]

@TonyT my apologies, plasterboard at the end, so commit to the boxes ahead of that being offered up

[Carrerahill]

On 25/01/2021 at 02:00, tanneja said:

...and 10 downlights.

 

I do not understand the fascination with downlights slapped everywhere. We finished our kitchen last year without a single light on the ceiling, whole lot is up lit from hidden linear sources with various colour temps and dimming levels, at full output we have about 550lux avg. at 0.9m (which is even greater than the required level for a commercial kitchen - we would not actually use it at full output except maybe when cleaning) and can dim to 0. Ceiling is totally unpunctured. Light quality far superior as there are no shadows anywhere and wherever you choose to stand and work you are never working in your own shadow. 

 

If your heart is set on them then how I spec it is 9.5mm PB on the ceiling, then frame it out for a service void, then 12.5mm PB over all of that. You have just created a service void that you can blast with a shotgun and still not damage your VCL/air tightness/insulation levels and removes the fire risk of downlights in PIR. 

 

 

Edited January 26, 2021 by Carrerahill

[Bitpipe]

I had to waterproof penetrations into my basement - the contractor cast in duct that each 110mm foul and the electricity and water supply came in through but for each there was a 5mm gap all round.

 

I used Newton Stopaq 308 (https://www.newtonwaterproofing.co.uk/products-systems/products/concrete-joint-and-leak-sealing/pipe-sealant-through-service-duct-sleeves/) its a flexible compound that never sets (is quite messy to work with) - you pump it into the cavity once the cables are through and then seal the exterior with a special cement.

[TonyT]

55 minutes ago, tanneja said:

@TonyT my apologies, plasterboard at the end, so commit to the boxes ahead of that being offered up

Yes, sorry that’s always my plan, as I don’t like plasterboard fast fix boxes. I prefer a dwang/noggin with a box fixed securely.

also better if you have flush plate accessories as they then go flush with the wall, as with fast fix, there is then a lip.

[MJNewton]

23 hours ago, tanneja said:

I was following @MJNewton in his quest for best lighting and he ended up with GU10 LEDS

 

I should note that I didn't have any height/clearance issues so didn't need to consider slimline fittings, so don't assume my decision to use GU10s was because the alternatives weren't any good (I don't know either way).

Edited January 26, 2021 by MJNewton

[TonyT]

I prefer GU10’s, to many fittings fail and the whole thing has to be removed and replaced also ensuring replacement fits in with existing.  Find it far easier to fit GU10 lamps and replace a lamp as and when required.