Calcium silicate?

[Kearn]

No need to use a plastic bound adhesive, it mitigates all the good work you’re doing. Wood fibre boards can be attached with a lime slurry, but better with the SS and plastic washers to mechanically fix as they are weighty.

Wood fibre boards and insulation batts, are both hydroscopic - I can say this with proof of having a leaking gable get attacked by a storm or three - the internally unplastered panels got soaked, then dried out pretty rapidly, back to where they started.

 

[Lacan07]

Many thanks. We’ve decided on wood fibre. Now just trying to get someone to install it.

No need to hack any plaster of the wall if its lime and you don't need adhesive either if the wall is flat (which it will be if its plastered). All you use is mechanical fixings, check out the guides, theres plenty out there. You'll need to work out how you're going to detail it round any window frames though.

80mm thickness is considered the limit before you risk moving the dew point into the fabric of the building.

 

[Maria D]

Regarding the window frames, would an insulating plaster only be sufficient?

 

[Lacan07]

Regarding the window frames, would an insulating plaster only be sufficient?

No, window frames are usually detailed with the same material (wood fibre) at the same or lesser thickness depending on how much room you've got.

I myself opted for PIR board as I figured the wood was already painted with plastic paint anyway. Its easier to work with, the U value is higher in comparison to the thickness used and I didn't have much room to work with.

If you're hiring someone to do this you'll need to discuss the detailing with them.

 

[Maria D]

That seems a sensible solution. What mm do you opt for both?

 

[Lacan07]

That seems a sensible solution. What mm do you opt for both?

Generally I opted for 60mm wood fibre on the walls and 25mm PIR board around the window frames.

The advantage of PIR board of course is that its easy to get hold of at any hardware store.

You go up to 80mm on the walls if you're happy to loose the room space.