The answer is “quite hard” apparently… but well worth it. Our wee cottage on Loch Fyne is idyllic but seriously under specified for Winter on the west coast. The walls were built with *zero* insulation – an inside skin of plasterboard, some air, and an outer skin of cedar cladding. It leaks heat like a radiator, meaning that you never get properly warm, and what warmth you can get comes at an obscene cost in terms of fuel.
So, as part of our “big works” ™ we are adding insulation to the walls – and not a small amount either.
all of the stages…
First, we remove the outside cladding from the wall, which exposes all of the internal gubbins of the wall – timbers, electrics, you name it. The first task is to clear out all of the dreck – mostly horizontal noggins which were there to support the external cladding timbers. We started using a variety of tools before settling on the multicutter (cracking bit of Bosch kit) for the timbers, then the angle grinder for removing the old nails (knocking them through and pulling the old nails was taking ages, and flexing the timbers like crazy… )
Once the bays were clear, the next step was adding 25mm battens to the back of each bay – this acts as a back stop for the insulation, leaving us with a nice 25mm service duct for running future cables and the like. Once the battens are there, the spark in me wants to see the mains cables all tidied up, clipped to the timbers and secured. The house was re-wired without removing the plasterboard, so a lot of the cables simply pop through a hole in the top of the wall and hang down to the fixtures – not good practice. once these are all secured, we staple the first of our wonder fabrics into place – we are using DuPont Airguard reflective as our VCL to help stop interstitial condensation and keep the place breathable but toasty. We are using Celotex PIR insulation, so there’s not so much advantage in using the reflective air guard rather than the regular stuff (only a couple of percentage points in it…) but out here on the edge of the world, facing into the weather off the loch, those extra points are worth it.
Once we have the cavity all lined, and the fabric stapled into place, we squeeze in some celotex. From my ukha days I remember the self builders raving about kingspan insulation, and I can see why. this stuff is insanely good. we cut the big sheets to size on Scotland’s most scenic work bench…
and wedge them into the bays. Once that’s in place, we add an OSB skin, also stapled into place with a proper nailgun/stapler. After that comes the *really* expensive membrane – seriously, this was over £500 for a 100 metre roll! It’s Tyvek reflex – again, the top of the line reflective stuff for an extra few decimal points of performance. This one doesn’t just get secured in place – it gets taped with aluminium tape across all of the staple marks, or any nicks and scratches to ensure it becomes completely draught proof.
On the outside, we add some timber battens, vertically first – these are humped into place with the “big” nailgun – my gas fired hitachi monster, which helps to secure the OSB and earlier stuff into place. on top of this – we put the same skanky old cladding board back on… for now! the plan is to replace these with a super smooth, dirt resistant, water repellent silicone based super-render in a few months (when the glazing gets done).
It’s shaping up really well. Now, we just have another 29 metres of wall to do!