Recycled green XPS issue
Hi there,
There is this company that recycles polystyrene and makes XPS sheets out of it. 100% recycled.
I placed an order for some XPS 2″ R10 with a PSI rating of 40, as I need to place them under a heated garage pad and heated driveway.
The order I received has a mix of new sheets with a normal white colour and of some that are changing colour, getting brown, most likely because they were seating outside under the sun till I bought them.
All the ones that are changing colour, have a crack at the same location.
I reached out to the manufacturer and they said its most likely bad quality control and are offering to replace them. I just found weird that only the “old” sheets are cracking.
The heated garage and driveway is a costly project and I am now worried that using this type of recycled foam will create some issues in the future. We can not have the foam break down under the concrete, especially with PEX tubing running through it.
This foam recycling company is new, they started doing this in 2022 so there are not many long term reviews.
Any suggestions?
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Replies
I doubt there's a connection between the sheets laying in the sun and showing cracks like that. XPS is extruded between forms and I imagine they had a mix ratio slightly off so the foam expanded more quickly than it should have, so in those areas the foam did not bond to itself adequately before curing.
Foam gets a sunburn just like we do, which breaks down the chemical bonds on the surface but should not affect the rest of the sheet.
Once the foam is protected from sunlight, the main thing that could reduce its efficacy would be insects that want to burrow in the foam.
I suspect that the crack and voids are due to a problem in the extrusion process, possibly incorrect temperature, which could be related to extrusion speed. Either way, poor quality control would fit (and would explain why they shipped product looking like that too). Discoloration can also occur when plastics are worked at too-hot temperatures.
If they're offering to replace the bad sheets, that shows they are trying to fix the problem, which is a good sign. The issue is if they missed something this obvious, my concern is that there may be smaller issues that might not be so obvious that you won't easily catch.
Can you use this material in a more accessible location (i.e. basement walls, behind siding, etc.), then use new material from a reliable supplier for the subslab insulation? I'd be reluctant to use a questionable product in a subslab application where replacing it is a HUGE problem.
BTW, I hope the company can get their process working reliably as recycling old polystyrene into XPS is a neat idea.
Bill