Green Building Forum - Extruded Polystyrene and Global Warming Potential (hydro-flouro-carbon XPS)

Extruded Polystyrene and Global Warming Potential (hydro-flouro-carbon XPS)

TimSmall — Thu, 16 Aug 2012 13:14:57 +0100

I've noticed that some people on here advocate the use of XPS below ground level - from the look of this, it looks like that needs to be CO2-blown XPS, otherwise it'll be doing more harm than good from the look of this:

http://www.greenbuildingadvisor.com/book/export/html/17147

... unless anyone knows differently, and you can now get lower global warming potential (GWP) XPS without dropping the k value too?

Extruded Polystyrene and Global Warming Potential (hydro-flouro-carbon XPS)

Viking House — Mon, 20 Aug 2012 23:21:37 +0100

Thanks Tim, good to know the figures.

Extruded Polystyrene and Global Warming Potential (hydro-flouro-carbon XPS)

wookey — Tue, 30 May 2023 15:51:42 +0100

Following up on this very old post, I was horrified today to find that in the US they are (or were until remarkably recently) still using HFC to blow XPS. It was banned in 2015, but they argued an exception till 2021 and even that has been stayed except in some states that got fed up of waiting and made their own legislation.

I thought this had stopped about 15 years ago when PUR stopped being made with HFCs and switched to pentane.

It looks like manufacturers now use HFO instead so the GWP goes from 1400 to 48 or so. I presume this changed in the EU some time ago.

https://www.greenbuildingadvisor.com/article/xps-makers-announce-more-planet-friendly-formulations and
https://www.greenbuildingadvisor.com/article/extruded-polystyrene-insulation-with-low-global-warming-potential (from 2021)
explain the details of the legislation and the manufacture, but fail to find out what Kingspan use (which I suspect is HFO from their website saying 'GWP <50').

https://www.greenbuildingadvisor.com/article/choosing-low-carbon-insulation (also from 2021) has some pretty scary numbers for GWP per 1m2/R(si)
XPS (HFC) 46
XPS (HFO/HFC) 8.8
PIR 2.3
graphite EPS 3.5
rockwool 3.2
woodfibre -7
fibreglass 0.7-1.6
cellulose -0.8 to -2

So you _really_ don't want to be using HFC-blown XPS. It's not clear from the article if any manufacturers are still doing this, in the US or elsewhere, or if it is finally dead. But it's depressing to see how long they persisted in this practice despite alternatives being available.

One wonders why pentane or CO2 can't be used for XPS blowing the way it is for other foams?

It seems that XPS blowing agents with a GWP <1 are now available: https://sustainability.honeywell.com/us/en/applications/foam-blowing-agents/xps-insulation

And as someone mentioned in the comments: does HFO degrade to a PFA?, in which case this is really just swaping a really bad air pollutant for a really bad water pollutant. XPS is marvellous stuff as a building material, but at the very least one should be reading the EPDs carefully and not letting builders and surveyors do random substitutions 'because it's all the same'.

Extruded Polystyrene and Global Warming Potential (hydro-flouro-carbon XPS)

djh — Tue, 30 May 2023 17:51:43 +0100

Posted By: wookeyOne wonders why pentane or CO2 can't be used for XPS blowing the way it is for other foams?

That's answered in the Honeywell literature. Those gases can be used as blowing agents but they then migrate out of the foam, leaving air in the foam presumably, with a relatively poor performance as a result.

It seems that XPS blowing agents with a GWP <1 are now available: https://sustainability.honeywell.com/us/en/applications/foam-blowing-agents/xps-insulation

And as someone mentioned in the comments: does HFO degrade to a PFA?

Indeed but that literature also mentions that the specific HFO is HFO â€“ 1234ze and according to wikipedia that is also known as 1,3,3,3-Tetrafluoropropene and "actually might form HFC-23 as one of its secondary atmospheric breakdown products. HFC-23 is a very potent greenhouse gas with a GWP100 of 14,800. The secondary GWP of R-1234ze would then be in the range of 1,400Â±700 considering the amount of HFC-23 which may form from HFO-1234ze in the atmosphere."

edit: So I'm pretty happy with straw, cellulose and graphite EPS in my house (in that order of quantities)