I’ve been having a google pending buying an old house and am a bit confused round the damp part.

I have renovated a few old stone terraces and generally just stripped back the wallpaper and made good with filler or had bad bits replastered. This time I thought I would try and add some insulation by using thermal boards dot and dabbed or battened with kingspan between.

So my confusion is, where there is no damp problem present am in danger of creating one by adding temperature differences to my walls?

You won’t increase the possibility of condensation forming on a wall by making it potential warmer, so no, insulating a wall won’t make it more prone to becoming damp.

Look on the insulation websites and see if they have a dew point calculator as you can cause issues by adding internal insulation.

Well ignore my comment and do as aP suggests then, mine was based on solving past damp issues by adding insulation to walls, but aP is better placed than me to comment on such matters 🙂

Is it a stoopid idea? Should I just stick to insulating the loft and fitting another log burner?

No, you won’t likely create damp problem if it is dry now. Yes it’s worth doing. You can add Kingspan, then a batten, then plasterboard drilling and screwing, then skim on top. I’ve done a few rooms now and it has transformed them(single skin 1901 place here).

Totalshell of this parish does a fair bit of this stuff and rather than all the drilling sticks the boards up with fancy foamy gunk. IIRC you also need a few mechanical (ie drilled) fixings to meet building regs (stops it coming away in a fire?)

Kingspan or all the other common boards are foil backed and you tape the edges up to prevent moisture going through from the warm room to the colder outer wall.

Tape the edges of the kingspan?

no, tape the gaps between the batts where they meet./

Its a foil tape.

Instead of doing it twice as above, why not just use something like kooltherm, thermaline or thermalcheck xp?

Are they all boards you just bond to the wall?

I am with Ap on this one. By moving the warm surface forward into the room you are insulating the original wall from the warmth, this means it will be colder and then you have the possibility of condensation. Condensation can lead to mold. I had the same question in my cellar and I was strongly advised to only insulate from the outside and never from the inside!

Vapor barrier :

Surely cellars are a very different matter?

Depend on numerous factors,

i.e internal condestion risk (laundry room / kitchen / shower etc) / heating / ventilation / breathability of the wall

It would be advisable to run a vapour check on the warm face of the insulation to minimize any Interstitial condensation risk. If you have foiled face insulation and tape the joints it will achieve the same effect or look for a laminate board which incorporates or achieves a vapour check.

If you want to be really sad have a read of BS 5250. ZZZZZZZZZZZZZ…..

If you use a PIR board go with a Class O rated product to avoid adding to the fire load. Even though its encapsulated it can still be a risk. (The manufacturers have responded in the last 4 or 5 years with fire rated products)

Cellars are different. The external ground is an insulate and therefore the risk is reduced.

Well, I think I’m suitably put off 🙂