Help needed - mistakes were made with EWI

[maznaz]

Hi there,

 

I'm DIY renovating a big old stone walled house and I decided I wanted to do it properly and got the local council building control involved. I got my first inspection after I'd taken off a load of old plaster from the external walls and was told by the BCO that since I'd done that I'd now have to insulate them all to a retrofit standard. I've never done that before so I went into R&D mode for a while and eventually arrived at a combination of internal and external wall insulation. The house is in a conservation area and semi-detached so full EWI wasn't possible.

 

Anyway due to my own error I ended up specifying and ordering PIR insulation (Recticel Eurothane GP) and attaching it to the wall. I told the BCO by email that's what I was doing but at the time he just said as long as the U value was met it was fine. Now that he's seen it in situ as the render is going over, he's correctly queried the suitability of PIR for this purpose. I was sure I'd read it was fine, but I can't for the life of me find anyone who can corroborate that. I really don't know what to do, as the budget being super tight was why I was messing around ordering bits myself rather than a full system from EWI store or similar. I can't afford to take it off and redo it. It's about 80 square metres total.

 

Does anybody have any practical advice? Is there any way to mitigate the weaknesses of this type of insulation for this purpose? I know it exceeds the U value we need and it's more fire retardant than EPS so I can't work out what would actually make it unsuitable. If it's just compatibility with render systems I can work around that.

 

Many thanks.

[Mr Punter]

It used to be possible to use pir in EWI.  Post Grenfell I imagine most of the certifications have been withdrawn.  Get in touch with a render firm (weber or whoever) to see what they suggest.  Could be tricky.

[ADLIan]

I’m sure PUR is ok for with render. Does this product have a foil face? This may be the problem as render will not stick, product for direct render normally has a glass tissue facing

[maznaz]

2 hours ago, ADLIan said:

I’m sure PUR is ok for with render. Does this product have a foil face? This may be the problem as render will not stick, product for direct render normally has a glass tissue facing

 

As far as I can determine that's the only factor that deems them unsuitable; the render adhesion. We did some tests and using thin coats of the render along with scuffing the surface of the foil we got a really good adhesion that held over the winter. If that's the only factor the BCO has said it's acceptable, but I need a definitive statement from someone, ideally Recticel that confirms that's the issue. Fingers crossed I guess.

[Conor]

We ha da ICF build, but wanted another 100mm EPS on the outside to get to passive house stnadard. The builder used 50mm PIR instead for the lower floor. So I over boarded those sections with another 50mm EPS. Used 100mm EPS on the upper floor that wasn't in the builder's scope.

 

You wont be able to render onto the PIR. Options are to fix cement (render) board, or a thin layer of EPS. You'll need mechanical fixings. No need to take the PIR off.