Is “low GWP XPS” insulation really that much better? – GreenBuildingAdvisor

The recent GBA article “Passive House Today” referred several times to “low GWP XPS insulation”.

I’ve been avoiding XPS in favor of EPS due to XPS much larger greenhouse warming potential (GWP). I understand that manufacturers are revising their XPS formulations to reduce the impact of XPS.

But is it really comparable to EPS now?

For example Dupont is making a big noise about the rebranding of its Styrofoam now that it has converted its formulation for all its Styrofoam products.

But how much better is it and how does it compare to EPS in terms of GWP?

Are there any independent 3rd party tests to quantify the improvement?

Also, the 2 areas where I typically spec EPS are as exterior insulation on roofs, and slab-edge and underslab insulation for foundations.

Is there any practical advantage (durability, longevity, etc) for using XPS over EPS in those applications?

And I guess while I’m on the subject, where does polyiso fit into all this?