Wiring and Insulation (pt 1)

Having battened out the inside we’ve spent the last week and a half running the wiring around the studio and fitting the insulation into the framed walls. We have the electrician booked for a week today and, by that point, I need to have run the wiring, insulated, and put up all the plasterboard – busy!

Last week the electrician came round to validate the wiring I’ve already done in the garage and to talk through how I was intending to wire the studio. As we have to have a new consumer unit fitted to get power out there he’s pretty happy that there’s enough work for him to make it worth his while. The wiring basically consists of a new ring from the new consumer unit in the garage running round the studio and up over the door, the bottom of the sockets are 470mm from the floor except for the one up on the wall to power the tv (picture 1). Lighting-wise there’s an external dusk-dawn light and an internal, overhead, set of spots – the junction boxes for the switching are in the top of the wall next to the door (photos 2 and 7).

When it came to the insulation I used a fine tooth panel saw to cut the 50mm Xtratherm panels to size to fit into the gaps in the battening, and about 30 seconds into sawing I stopped and fetched a fine dust mask – it’s a messy business that generates a lot of dust. Once I’d filled out the voids in a section I ran over the joints with foil tape to seal it all up.

A couple of points worth noting:

  • Photos 4, 5, and 6 show how I was insulating around the sockets. I used a section of 25mm Xtratherm behind the sockets on top of the noggin with a notch cut through to feed the wire with another panel of 25mm Xtratherm on the front around the socket to pad it out. In this way (with the 35mm back boxes) the back box protrudes 10mm out from the insulation ready to have the plasterboard put round it.
  • The above socket insulation method will also (hopefully) prevent condensation forming on the back of the backboxes as they are likely to be the coldest part of the overall wall.

Though this was the design/plan I’m not that concerned about condensation in the wall. Why not I hear you ask? Well I’ll tell you…

To allow for the expansion and contraction in the external structure I built the internal wall standalone so that it wouldn’t be affected. As a result there isn’t actually a very good seal behind it and so moisture is never going to get trapped there as it can always get around the edges. I don’t know what impact this is going to have on the performance of the insulation (I hope not too significant) but it does make a bit of a mockery of [1] my use of the foil tape and [2] the foil backed plasterboard I’ve ordered for the walls. Oh well.

Costs

  • 50mm Xtratherm insulation (11$): £242.00
  • Foil backed plasterboard (14$): £140.00
  • Foil tape (4 rolls): £10.00
  • 5mm ply for flooring (4$): £20.00
  • Metal backboxes: £15.00
  • 2.5mm and 1.5mm twin+earth: £40.00

Lessons

  • If you’re intending to fit insulation between your framing make sure that you position the framing consistently and exactly. I allowed the framing to wander by a few mm here and there and, if I was insulating over the top, it wouldn’t be a problem however, in this case, it meant I needed to measure and cut each piece specifically – annoying.
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