Cavity wall insulation-causing problems?

[GeoDIY]

My mum had cavity wall insulation installed in her 1970s detached house about 2-3 years ago. Since then we've noticed mildew appearing on the interior of some of the external walls,primarily in the corners and around the windows and at the same time the interior painted walls have started peeling in the same areas. In addition,the wood window sills have started cracking and the paint peeling-almost as if drying out. She has put it down to just wear and tear but I can't help but think its related to the instalation on the insulation. As far as I can see there was no additional ventilation added. The final straw has come this winter when the render has started to blow. The guy who came around to look at it called it onion skin weathering and said it was due to the cold weather and completely normal. But I don't see anyone else's houses with the same problem and I know my mum's re-rendered her house more recently (10 years ago) than most others. I might just be being paranoid but does anyone have any thoughts on this? She's looking at a 4k bill for the render and doesn't need to be getting into this if its going to blow again the next time we get frost!

 

[jeds]

The cavity insulation might be responsible for the internal poroblems. If the cavity fill is not complete it can cause cold spots which will attract condensation. It's particularly common in the corners but then condensation is common in corners anyway. The only way you will know is to inspect the cavity to see if it is completely filled. If not then it should be guaranteed.

I can't see how the cavity fill could be connected to the external render problems though? Much more likely to be poor rendering in the first place or incorrect render specification. Waterproofer in the render mix more than likely.