I sometimes think that we, with our houses, at this stage are still 'benefiting' from the well-understood standard way of building that prevailed right into the 60s/70s, when my architectural career got going. Since then, everyone's been inventing novel ways of building, for good reasons.

Just about any existing house that I'm called upon to alter/update, I can still see or reliably deduce what's 'under the skin' - which I then proceed to confuse by today's ever-changing idea of novel methods! Maybe some of those earliest novel methods are few enough that I can recognise them OK, as they get old enough to want modifying.

If people are still modifying their houses in 20/30yrs time (and I wouldn't so predict the future, as a extrapolation of our ever-more-unaffordable labour-intensive present practice), they'll find, on opening-up, a lot more odd, unadaptable constructions to make the best of.

Posted By: RexHave a new neighbour in a 1930's house and they are having the place re-wired. Obviously, it mean removing all the wiring that is covered with plaster.

I confess my ignorance. If you rewire a house, do you have to remove all the old wiring, or can you just put new wiring in as well?

Also, does Warmcel form [glued together] lumps after it is installed or does it remain a loose powdery material? (I think I know but I'm not sure)

I rebuilt and insulated a room, finished just in time for Christmas just past, intello membrane everywhere.

Now it's January and I've used the room a few weeks and realised the light switch is in the wrong place and I need another socket. Trying to work out how to do that without disturbing my painstaking airtightness work.


It's unwise (of me) to assume that wiring changes are someone else's problem for 50 years hence!

Posted By: WillInAberdeenNow it's January and I've used the room a few weeks and realised the light switch is in the wrong place and I need another socket. Trying to work out how to do that without disturbing my painstaking airtightness work.

Light switches are a solved problem nowadays. My preferred solution is a kinetic wireless switch. There's an RF receiver+relay that gets wired in the power circuit near the lamp and the switch itself is just stuck on the wall surface. It needs no batteries; presumably uses piezo to generate an RF signal. There are also wifi/zigbee ones that do need a battery but allow for integration into your smart home (whatever that is )

Sockets are more of a problem since they need a power connection. But in general that's why you put a service cavity in front of the VCL and behind the plasterboard.

Post crossed with DJH. The wiring for this house is all in the loft, so any change always means feeding it through the VCL/AT somewhere, even if just removing old stuff.

Posted By: WillInAberdeenPost crossed with DJH. The wiring for this house is all in the loft, so any change always means feeding it through the VCL/AT somewhere, even if just removing old stuff.

But that means you only need holes in the plaster rather than chasing channels? Plus some Siga Rissan tape to patch the Intello.

edit: Ah, presumably you need to make a vertical channel from the ceiling to wherever you need the new socket. Duh! Anyway, that's what you need a service cavity for.

I did want my Warmcel to be damp filled but the company who were going to do it, went into liquidation. the next company told me that the 180mm was too deep for damp fill, so had to scrim everything and they blew it in.

Although they hit all the density marks, I later had the need to do some extra work at the top of a couple of walls and found there to be large compression gaps in the Warmcel. In my opinion, the Warmcel had slumped, which frankly, is hardly surprising when you consider a 2.4m high column of blown fabric with no supporting restriction to prevent slumping. No matter the density feedback from the top of the cavity, gravity will always give greater density at the base.

They guys had to come back, remove 100mm diameter holes at the top of virtually every cavity, add some more Warmcel then I had the massive job of replacing, filling and flattening all these holes.

I was not a happy bunny! I am now convinced that there probably gaps at the top of every wall, but ignorance is bliss so not intending to find out!

Damp would have been so much better.

Before sheathing/plasterboarding/scrimming, before blowing-in, I specify light galv garden wire @ 400 vertical c/s, woven horizontally in-out-in from stud to stud (or rafters), so running diagonally across each tween-stud space, wound round a nail head to prevent it sliding down the stud. Gives the Warmcel something to grip around, as it consolidates.

Posted By: Rexalso wondered, perhaps it could be done twice. Half fill the first pass then when a bit dry a few days later, repeat to completely fill.

But that would have required two visits, and maybe twice the cost?

In my case, there is actually a batten/service space between the intello and the plasterboard, and that's part of the problem. I really don't want cold air to blow around in that void.

The space is on the inboard side of the airtight membrane. The main wiring for the rest of the house is on the outboard side of the airtight layer, in the loft.

Therefore any new wiring has to puncture through the airtight layer somewhere around ceiling level before running down the wall in the void.

Access to the membrane to make/seal the puncture is complicated because I have to cut out an A4 size section of the plasterboard, wallpaper, battens, coving to access enough of the membrane at its wall-ceiling junction to be able to apply a wide sticky patch.


An electrician would have no qualms coring 15mm holes to feed the wires down from the loft into the service cavity and would only fill any cosmetic bits, leaving an open hole from the loft into the service cavity to blow cold air all around the room. (Don't ask how I know this to be true!)

And I heard airtightness gury Paul Jennings asked 'how long do initial airtighness test results last, before deteriorating?' - he answered 'six months' and he put that down to sticky tapes beginning to develop tiny gaps, 'tiny' being quite enough to cause significant initial effect, which only grows but at declining rate, proportionately, after that initial jump.

From which I conclude that expensive sticky tapes are to be avoided, by using structural materials, not membranes and tapes, as the airtightness layer, including designing-out the numerous tricky corners and junctions that conventional-wisdom airtightness methods still create, for which sticky tapes are the only solution, if only you could actually get your fingers in there. Prime, advised, culprit being to put a plastic membrane too far inboard, where it's penetrated by numerous objects like joist ends. Instead, put the airtight layer (and similarly, the insulation) right outboard, where it can form an unbroken 'tea-cosy' right from roof-ridge down to foundations - easy if you think it out. Then the very few penetrations necessary, such as yes, flues, mains electricty incomers, can be designed individually, ingeniously, with wodges of quality sealant injected into deep joints of controlled width, scrupulously clean, never with sticky tapes.

Even rampant tradesmen, in future, can be guarded against, by choosing structural airtightness materials such as blown-in Warmcel which even if only 'moderately airtight', coupled with e.g. ply or OSB3 sheathing gapfilling glued-and-screwed/power-nailed, also 'moderately airtight', add up to 'pretty good airtightness' but with the advantage of easy cheap foolproof installation, long-term sustained robustness, and relative immunity to random hole-making in future.

Yeah, internal wet plaster or external render are good structural airtightness layers, which can be inspected and remedied - but still with great problems at their edges.

Posted By: djhI still think service cavities are a good idea. They should be filled with a 'wool' insulation to reduce or eliminate air movement without restricting the passage of cables etc.

If you put insulation in the service void then you should refer to the relevant de-rating table for the cable de-rating required for insulation one side or cable imbedded in insulation as appropriate.

The talk of wireless connections is fine, but unless you continually (well occasionally) change batteries, you still need power to the wall switch positions, to power the wireless controllers.

What you don't then need is the switch wire which makes things so much simpler. I'd use a star layout with loose wires pulled in conduit - the French do this part right.

For insulation I used Icynene and it hasn't gone anywhere! I would definitely use it again. I'm a FosterTom fan of the teacosy. My amendment to that is a double stud wall. One - internal for structure and the second outer one to minimise cold bridges and allow the installation of window shutters. Finished with cladding of some sort. Minimal concrete/bricks etc!

New design is all in my head - all I need is land and money

Posted By: borpinThe talk of wireless connections is fine, but unless you continually (well occasionally) change batteries, you still need power to the wall switch positions, to power the wireless controllers.

That's why I like kinetic switches; they don't need any power supply at all.

FWIW I have a bunch of Govee T&H meters with batteries. Now I've set them up with rechargeable batteries it's just a background routine thing keeping an eye on their batteries.