Celotex Shrinkage

[jayc89]

Came across a guy on Facebook claiming Celotex shrinkage is pretty bad and then posted this;

 

 

Never seen anything like it

[jayc89]

[MikeGrahamT21]

Thats got to be a faulty batch.

 

I've had PIR in the loft which is years ago (odds and sods), and still looks the same as it did when i bought it

[Mr Punter]

It seems to deteriorate when exposed to the weather.

[SteamyTea]

Polyurethanes can shrink quite a bit.  We used to work on 3 to 5% depending on the mix.

Some of the fast setting elastomers can easily be 10% and continue to shrink for years (Look at a Panther Kalister dashboard, it was a perfect fit when I made the tooling).  Think how plump your new furniture was compared to when it is a few years old.

I have heard that you can buy 'aged' insulation, but not really convinced it is of any benefit.

 

As for the picture, that looks like something went wrong in the manufacturing and storage.  Probably it got wet somewhere along the line as it is warped and shrunk (warping is actually caused by shrinkage, think bimetalic strip).

It is not a unique problem to just polyurethane, really a problem for all composite materials.

[Conor]

I've sheets that have been sitting outside in the elements for over a year that look way better than those. Looks like all the walls will have to come down?!!!

[saveasteading]

That is date stamped 17/8/11.

I wouldn't be surprised to find it is second hand, and badly stored at that.

The top ones are smaller, maybe cut out of bigger sheets.

 

I used a load of salvaged PIR in my house, and it handled as if new. I think it does shrink but not much. It would take some effort to bend it as shown.

 

So don't worry about the product in principle. 

 

 

[Tims]

A neighbour tried to sell me some like that that his builder had left when he'd kicked him off his job. It was obviously ripped out of some where and then stored out in the elements for some time and had a similar date stamp. I pulled some out of a dry 15 year old conservatory floor that looked perfect, so I expect that the stuff shown has had a hard life and been out in the elements for some time.

[Iceverge]

https://475.supply/blogs/foam-fails/foam-fails-reason-5-excessive-shrinkage

 

https://www.rdh.com/wp-content/uploads/2017/06/Long-term-Polysio-Movement-and-Thermal-Performance-Study.pdf

 

 

Alas it does. 

 

"Dumb" insulation with K value of no less than 0.032W/mK is a better bet long term. Cheaper too. 

 

 

[eandg]

Used fairly fresh Celotex in our build, which had mostly been up for 6 months until the sheets of plasterboard have closed in around it over the past few weeks. Any gaps foamed and taped. Zero shrinkage. PIR in loft will remain exposed unless I can be bothered sheeting it so will be a good wee experiment to see if that changes. 

[nostos156]

On 05/07/2023 at 00:18, eandg said:

Used fairly fresh Celotex in our build, which had mostly been up for 6 months until the sheets of plasterboard have closed in around it over the past few weeks. Any gaps foamed and taped. Zero shrinkage. PIR in loft will remain exposed unless I can be bothered sheeting it so will be a good wee experiment to see if that changes. 

 

Yeah, I got 50mm insulation in January, and it took me until around April before I got it all installed and foamed in. Then it took me until the beginning of July before I got the 25mm stuff in (which was date stamped late November last year, so has had time to offgass already, since it seems the majority of it happens directly after manufacture).

 

Haven't seen any evidence of shrinkage while in situ yet.

 

From what I can tell, aside from bad batches, it's UV exposure that kills this stuff. Probably what happened to that stack.

Edited July 18, 2023 by nostos156