celotex / kingspan losing insulation performance

[sm_jamieson]

Several reports around about PIR / PUR type foam (the gassed types) such as celotex / kingspan losing insulation performance due to de- gassing and ending up with the same R values as expanded polystyrene. Some suggest after just 10 years. Surely if this is true, it is a major situation. If you were building a super-insulated house it would be a major factor. Since polystyrene is usually cheaper, you would surely use this. It almost seems as if this feature of the foam boards is being hushed up. Can the foam boards really claim their properties if they only last a few years ? Many buildings are slowly losing insulation performance as energy gets more expensive ? Really these boards are just a way of satisfying building regs where space is a premium ? Simon.

[The Natural Philosopher]

Plystyrene is extremely flammable and I would not use it for that reason alone.

It is the first I have heard of it.

But it certainly is worth further elucidation. Where did YOU hear of it?

[Robin]

Yes but that's taken into account in the values cited for the boards. The published figure is based on the predicted 25 year performance. It's all dictated by a European product standard.

[The Other Mike]

So presumably after 25 years or a bit more you need to rip up concrete floors and take down walls to replace it?

[Robin]

Oh yes of course; and ISTR it's strongly recommended that you do it yourself, from inside the house, using RPGs. With good quality video there is then the added bonus of a chance of a Darwin award.

[The Other Mike]

Surely no need for an RPG, just an angle grinder...

[Man at B&Q]

Here we go again...

Except for the stuff that contains flame retardent.

MBQ

[Tabby]

the figures

NT

[Robin]

of date - at least as regards Europe. It fails to cite the European standard EN13165 which was compulsory from 2003 onwards. That requires an estimate of the average lambda value during 25 years of use under operational conditions. The fact that most of the change happens during the early years as gases diffuse mean that's a pretty good approximation to the value in later years. See eg

[John Rumm]

Care to cite some so we can have a look?

If that is the case, then it seems hardly worth worrying about - you will have recovered the extra cost of the insulation in that time anyway.

Not really - not least because the other physical properties are less desirable, and the range of products less broad in the first place.

[sm_jamieson]

Ah, not really official reports, more hearsay I guess

But you'd still need to use thicker boards to allow for the degradation, if you were after a particular thermal performance. However, it seems this is allowed for in the specifications, at least for around

25 years (since when was that a long time ?).

I remember seeing a Grand Designs where they used something like 1 foot thick expanded polystyrene (e.g. jablite) all around and under a basement.

Simon.

[Robin]

AIUI the standard requires the performance over 25 years because, among other things, that can be measured with a reasonable degree of accuracy by advanced ageing techniques. The additional point which I don't think has yet been made and which you then need also to consider is that the known[1] ageing effect is the diffusion which replaces the gas used to blow the foam by air. That is of course a process which approaches (asymptotically I think) equilibrium - i.e. when it's all air. As for most foams that happens well before the 25 years are up then the specified figure is good beyond 25 years.

[1] Of course there may be unknown ageing effects. But my impression is PIR foams have been tested rather better than eg Rumsfeld's plans for Iraq

[js.b1]

The problem is pentane migrates out over time, being replaced by air.

The EN test supposedly considers this, but there are confounding variables here.

- Installation quality is far more important re gaps etc

- Aging techniques may not have real world efficacy

- Edges could be foil taped to slow down gaseous exchange

Last time I talked to Fischer & Celotex they both recommended people pin the Celotex to the wall, tape all joints, so eliminating all the gap problems then pin battens or plasterboard directly to that (hammer fix or the various fischer type insulation anchors).

For known damp solid walls I prefer cement based tanking (Mapei Keraflex) with extruded polystyrene bonded on top.

Remember if using metal insulation fixings into known damp solid walls (water) with black mortar (sulphuric acid) then to ensure they are stainless otherwise you will be creating a future industry repairing horizontal mortar cracks when the fasteners corrode and expand.