Ducts for wires through external insulated walls?

[Dreadnaught]

My timber frame is up. The 240mm walls are empty, without insulation. Soon they will have Wamrcel (blown cellulose insulation) pumped in. 

 

I am thinking about the various wall penetrations. I assume that they need to go-in before the Warmcel.

 

What about wires for external lights, external power sockets, and the door bell? Should they be ducted through the exterior wall? Or just as wires and, presumably, derated?

 

Any advice would be welcome. What have others done?

 

[ProDave]

Put 20 or 25mm PVC conduit through the wall, sealing both ends to the timber.  Later once you put the wires through, seal that at both ends to maintain your air tightness.

[markocosic]

Cladding?

 

Bunch them up into as few entries as you can then run the cables behind the cladding to their final destination?

 

(e.g doorbell and outside light to share a single penetration)

 

Aside from chimney and mvhr entry/exit we're putting everything else through the floor then running it up behind the cladding to final destination. Minimises the number of penetrations and makes it pretty darn hard for things to get wet.

[Dreadnaught]

18 minutes ago, markocosic said:

Cladding?

 

One side: Cedral Lap planks over battened ventillation void

Other side: brick slips over over battened ventillation void

 

Thanks for the advice.

[TonyT]

While the regs give guidance on derating cables totally surrounded by insulation for more than 50mm length in insulation.

I think I wouldn’t bother worrying about it,

I wouldn’t want mains cables next to data cables( wired video door bell springs to mind)

but would just make sure they are sealed as per ProDave’s method.

[Onoff]

18 minutes ago, TonyT said:

While the regs give guidance on derating cables totally surrounded by insulation for more than 50mm length in insulation.

I think I wouldn’t bother worrying about it,

I wouldn’t want mains cables next to data cables( wired video door bell springs to mind)

but would just make sure they are sealed as per ProDave’s method.

 

Erm...500mm

[TonyT]

 

[Onoff]

Just now, TonyT said:

 

 

Fair enough & to think I have my 18th ?

 

Why am I thinking 500mm? 

[TonyT]

Wasn’t that if it was more than 500mm you had to half the Current carrying capacity of the cable as a general rule of thumb 

[saveasteading]

5 hours ago, ProDave said:

once you put the wires through, seal that at both ends

You can get grommets to make  a tidy seal, but you should also fill the void. ProDave will know if they are easy to get at merchants.

[joth]

6 hours ago, Dreadnaught said:

Any advice would be welcome. What have others done?

 

FWIW where it was just one wire going out (external light / socket / speaker) we drilled through the whole lot with a 2 foot auger drill after the warmcell was blown in and sealed. Then  fed the cable through a pro-clima grommet and then through the wall. Grommet taped down to the OSB airtight layer. This seemed simpler and allowed lots of flexibility in placing the wire much later in the process.

 

In places where there's a bunch of services going through, we did the duct through the wall approach. For BT/virgin cable, I did debate running the duct all the way from the wall up to the AV cupboard, so new services (fiber etc) could be pulled right the way through in future, but decided it was too much effort and liable to snag anyway.

 

https://www.ecologicalbuildingsystems.com/products/airtight-windtight-systems/pipe-and-cable-sealing/grommets

https://www.ecomerchant.co.uk/walls/airtightness-products/service-grommets.html

[Dreadnaught]

Thanks @joth. Tips from those who have been there before are my favourite. Useful advice.

[joth]

2 hours ago, Dreadnaught said:

Thanks @joth. Tips from those who have been there before are my favourite. Useful advice.

Pleasure! 

Forgot to mention the usual tip, angle the drill slightly downward on the way out and loop the wire downward on the outside, so if any weather does makes it way to it, it won't travel back along it into the timber frame. 

[Pocster]

On 05/01/2022 at 10:48, Onoff said:

Why am I thinking 500mm? 

Because a part of your appendage is the same length.

Edited January 6, 2022 by pocster

[Pocster]

17 hours ago, joth said:

Pleasure! 

Forgot to mention the usual tip, angle the drill slightly downward on the way out and loop the wire downward on the outside, so if any weather does makes it way to it, it won't travel back along it into the timber frame. 

I did this. But when Virgin installed their cable through ducting they didn't do this. For 2 years no issue. Then for weeks I saw little patches of water on the floor but couldn't see any evidence of how it had entered the build. Then one day I hear the fateful "drip" - ran into the room with my torch and saw it. Water tracking along their internet line through narrow ducting. Let the rain stop. Then foam gunned as far in as I could. So far so good .

[Dudda]

If using PVC conduit (which is what I did) and as suggested by ProDave above, have it at a tiny slope or fall to outside.

 

If doing as markocosic suggested above coming out at the floor be careful with outside ground level. If you've a level thresshold you run the risk of having moisture coming inside. 

Additionally bunching them together makes it a tiny bit harder to seal so extra care and attention is required. I find it's easier to seal and airtight individual cables than a bunch. 

[Onoff]

Better than ordinary "mastics":

 

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

[Hobbiniho]

its dielectric grease, grease thats safe for electrics/electronics, means it wont go hard and brittle and will allow movement while also staying sealed, the sparkies at work use it a lot to keep water out of JB'S/ connections, only down side is the mess it makes although in a tube like that maybe wont be too bad