LOL

Arthur, its not expensive really. About £5 /bag. I just like to minimise the air spaces.

A general problem as I see it is that it is easier from a fixing point of view to just use blobs of thicker [texture] adhesive, which results in good air circulation in the voids - something which seems common, but which we don't want.

Covering the whole surface would be too hit and miss in my opinion. Using wet ribbons [only on flat surfaces] is a compromise which I find works well. I don't use this dot and dab on uneven walls anyway.

Very difficult to ensure an even spread of adhesive over the full area of a plasterboard and impossible to check how much of it is in contact with the surface your sticking it to - hit and miss. Getting the consistency right would also be a challenge as this will vary with the profile and porosity of the substrate. [Very dry walls would take in the water from the adhesive quite quickly reducing the time you have to get the board flat/plumb. Using ribbons of adhesive avoid these problems but you still have to match the consistency to the background as with all wet applied systems.

Back to normal - uploading won't work

Thanks Paul, It turns out it was the no of pixels as you suggested

Posted By: tonySo do how do your lot stop wind whistling arround behind the linings Paul?

Easy! Just make sure the external structure is airtight to begin with by using an air barrier!

Or, as is the case in our new house, the vapour barrier is foil-faced foam board that is installed on top of the studs (and taped at joints and sealed with acoustic sealant at change of plane) and then the furring strips are applied on top of that and then the drywall is screwed to the furring strips. No whistling wind at all.

In my on going renovation of an old brick house, the original plaster and lath has the lath nailed to battens which are nailed into wood strips that are embedded in the bricks at three different levels. In a couple of cases where the plaster and lath was removed (for various reasons) we put up foam board and then nailed furring strips through this into the nailing boards in the brickwork (after marking where these were. For the electrical outlets in a couple of cases where the wires were behind the foam board, we used "air tightness boxes" and taped and sealed these to the insulation to prevent any drafts. Drywall on top and everything is nice and tight. In a couple of other places we left the damaged plaster and lath in place, screwed foam board on top and then furring strips on top of that and did the same air tightness box trick for the electrical outlets (same thing in the ceilings too). We also spray foamed between the boards and the rim joist where necessary. All in all, no whistling behind any of the linings no matter how hard it blows outside.

Paul in Montreal.

p.s. I wasn't concerned about thermal mass either (in the old house) - there's so much wood in the house anyway that the temperature is very slow to respond to external changes. The 1.5 tonnes of wood we just laid on the upstairs floor has quite considerable thermal mass ;)

Posted By: arthurPaul, would be "it doesn't matter". Correct? You don't think air movement (convection) within the airtightness barrier will affect the insulation's performance?

In the brick house example, did you use a parge coat or just rely on the taped foam boards for airtightness? If the latter, don't you have moving air between the bricks and insulation which reduces performance? As Tony might say, doesn't it leave you with a tent of foam board within the brick structure and so not utilising the potential u-value of the brick layer itself?

I think preventing outside air from getting into the insulation in the first place is the most important aspect. Convection currents are driven by temperature difference so, in a solid foam situation, the air between the board and the cold wall will not have much of a driving force, neither will the air between the foam board and the plasterboard.

In my case, I didn't parge the brickwork (it wasn't practical to do this) and in some cases the brickwork was three courses thick. So there may be air between the brick and the foam board - which was carefully taped and foamed to make it as airtight as I could - but no real driving force to get that air to convect. As for the U-value of the brick, even three courses is not that much - equivalent to a 2x4 really (not even). Over here with the imperial R system, pine is R-1 per inch and a common 4" brick is about R-1 as well.

I also didn't add much insulation - just 12.5mm of polyisocyanurate - though this halves the heat loss of the wall but, hopefully, still allows enough heat through such that the brickwork won't get damaged by damp or frost.

And, all that said, air leakage is still around 38% of my total annual heat loss.

Paul in Montreal.

is it possible to dot and dab EPS onto an internal masonry wall and then plaster over? I know render is used in this way for EWI, so why not do it this way internally? This seems like a cheap and breathable option and has advantages compared to common practice of internal stud work with insulation between studs (no studs so more insulation, no thermal bridges and no timber / metal frame to degrade). Also cheaper than EPS backed plasterboard. I can't find any suppliers of >45mm eps backed plasterboard.

sure, fixings are a good idea. Has anyone plastered onto EPS?

what would be wrong with the standard renders (as opposed to the high tech ones)? Expensive and thick?