Draughts between Kingspan and uneven walls?

[George (dicegeorge)]

The walls here are very uneven, so if i fix kingspan directly to them there will be draughts up the back.

Should i fill the gap with fibreglass or what?

and in future should i leave the crumbly old plaster on the walls and fix the kingspan over it?

[The Natural Philosopher]

Draughts up the back are less of a problem than draughts coming through from the outside to the inside.

However overall airtightness is always useful as long as you dont have damp INSIDE that vapour barriers, when you need them to keep things dry.

The modern trend is to buld a house like a sealed polysyrene bucket: it dosn;yt matter what happens outside, because none of it gets in. Unless you explicitly ventialte it etc.

Older houses do not necessarily work like that, and there are two schools of thought..one is to let them leak to avoid the damp problems, the other is to tackle the damp and then seal them up.

I will get shouted down, but frankly, if at all possible, the latter is the better approach from an energy efficiency and comfort perspective.

The real question is, where are these draughts coming from, and can water get in the same way?

If it can, leave the gaps. If not, seal em up. Moving air strips heat far more than still air, Insulation is, after all only a way of keeping trapped air, still...