Foam CWI for retrofit

Ahh, I thought of the batts and modern CWI.

Blow in more mineral wool? 2k to remove it sounds ridiculous. The same contractor that blows mineral wool will know how to remove it ok. Then get them to fill it again, I’m sure that would be much cheaper.

Unless you need the air control. Is there a way to apply an air control layer in cavities before blowing mineral wool?

In The Netherlands they paint Blowerproof on the cavity side of the inner leaf as they build the cavity, but fitting an air control layer in an existing cavity does seem rather improbable.

By having the membrane in the cavity you minimise the risk of future damage.