Degradation of PIR insulation

BlondieR

Hi, I had finally decided to go with PIR insulation for my new build but have been reading that it degrades over time. (Lambda 0.023 - 0.028 over 25 years). Is this true & if so what happens after 25 years?? I do not intend to pull down one wall to refill the insulation... EPS seems to have a more proven track record and is about 40% cheaper though with a lower u-value. I am not bound to a specific energy rating by planning but was hoping for A3

Any recommendations?

Carlow52

a link would be useful.
is this degradation due to de-gasification or wha?

Not my area just wondering

BlondieR

yes, it was a thread I followed on Green building Forum.co.uk but I can't get back into it.

BlondieR

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6188&page=2


here is the link

sydthebeat

off gasing just means that the pentane gas is replaced with air.
even is the lambda incresed from 0.023 to 0.028 it would still be better than most EPS insulations which tend to be in the region of 0.033-0.038

what would influence the u value performance on a much more significant scale is the workmanship in installation.

Slig

PIR is manufactured by trapping gas in its voids, EPS uses Air as the insulating gas. This is the main reason that PIR performs better and also why its more expensive.

A more important thing to note is Degradation rather than degassing though. PIR shouldnt be used in a damp environment unless it is specifically designed for wet use. Standard boards fall apart if they get damp, they get crusty and brittle and just flake away. EPS is the best product to use in these areas even though it has poorer insulation properties and may need a bigger cavity to get you the same U-value it wont degrade or de-gas. I would only reccomend PIR in areas such as ceilings or stud walls where it will stay dry. In cavities and under floors I would larger quantities of the cheaper EPS boards