I'm somewhat perplexed as to why no recognized ICF system manufacturer doesn't make a polyurethane solution that is utilized in a similar fashion to the EPS/XPS polystyrene. Based on all of my reading, the R-value was far superior to alternative products, but all I can find is spray-on PU. There was a single company out of Orem, UT that apparently went out of business. EnergyForm was their name. They released their product at WOC in 2008. Thanks for your input/help.

just speculation here but maybe it has something to do with the ease of making precise forms out of EPS versus polyurethane?

I know of two knock-down systems that you can use any type or thickness of foam .

Polycrete's P2 product was made from polyurethane, but it was way too expensive for the North American market. It did get some traction in Asia.

On a dollar per R value basis, EPS is far superior. Even more so in colder areas (where PU loses a little bit of R value).

Not if you use recycled poly. that comes in at a fraction of the cost

I think the main reason is the fact that it is extruded. So the shapes are only 2D. It would be hard to make the 3D interlocks as well as the webs into the block.

I was thinking it would be nice if they made it. But for the extra R value you can just add the extra internal form from most manufacturers

Most experts ESPECIALY Green Pushing Experts would not agree and do not agree. PU has almost two times the R-value. It is not that much of a difference in percentage lost between the two as temps drop near 35 Deg. F. The reason most experts disagree. YES PU is about 50% more cost initial. However, in 2-3 years in MOST cases you make up the diff in cost of HVAC and electric. Also that extra 50% in initial cost you can often get back in Federal, State and private program incentives (as a homeowner). Then every single year after the initial 2-3 years is then profit in your pocket. Then there is the fire factor. One melts at less than 240 deg F. The other PU withstands more then 800 deg F. And then when fire does touch it is chars instead of burning or melting like the other. PU also has a GREAT DEAL LESS off gassing. Unlike the other, it is not known as a carcinogen. That is also great for overall health. .

You realize you're responding to a thread that's more than an a year old, right?

But responding to the points made:

In terms of $/R per square foot, polyurethane is MORE than 1.5x as expensive as EPS, it's more like 1.7-2x the cost. I'm not aware of any Federal State or private subsidy incentives for PU offered that somehow covers the cost delta, but I'd be much obliged to know where those incentives are being offered.

It's unlikely that the very real cost difference would be covered by the difference in energy use due to lower low-temp performance in 2-3 DECADES let alone 2-3 years, even at code min levels. Maybe if you were heating your house by burning $10 bills in a wood stove you could even shorten the pay back to 2-3 days, but even there it would still be important to show the math. In most analyses using real fuels & costs there isn't always a case to be made for the cost of R13 fiberglass vs. NO cavity insulation in only 2-3 years, let alone the perforamce difference across temperatures at the same labeled R-values between two foam types with different derating/uprating curves.

MDI outgassing of PU has known health risks, particularly to asthmatics. The bigger health question mark is on the fire retardents used (for all polystyrene, polyurethane & polyisocyanurate foams), less so the outgassing from the polymers themselves.

The melting point of polystyrene is 240C (464F), not 240F. EPS will start to shrink and deform at temps as low as 220F or even lower, but that's not the same as melting into a flowing liquid.

The assertion that "...PU withstands more then 800 deg F..." isn't supported by the available test data. The ignition temp of PU foam in the presence of flame is under 700F, and can be as low as 600F. The withstands 800F+ is apparently cherry picked from ASTM D1929 test conditions where there is no active flame from other sources, only flash temp when subjected to hot air.

Molten polystyrene doesn't self-ignite until it's over 800F, but foamed EPS & XPS will flash in the ~650-750F range in the same no-flame ASTM D1929 type tests. That's something lower than 850-1000F where most PU foams spontaneously light off in the same test, but both foam types have comparable ignition temps in the presence of flame, which is the more realisitic ignition scenario in a residential building.

In other words, if your house is already on fire, both become fuel to the flames at about the same temperature, but PU can't drip flaming blobs of burning goo when fully engulfed the way EPS or XPS can. That's really only relevant multi-story ICF buildings or EPS SIP roofs, where gravity can cause an EPS fire to move downward rapidly, whereas that won't happen in quite the same way with PU.

The HFC245fa blowing agent used for 1.5lbs+ density PU is a powerful greenhouse gas (nearly 1000x CO2), compared to the pentane used in blowing EPS (about 7x CO2), most of which outgasses at the fabrication plant, and is usually recovered and burned for process heat. In the US there is an impending change over to very low impact HFO1234_ _ variant blowing agents, but SFAIK only LaPolla has made that shift to date. Water blown 1.5-2 lb PU is also possible (with a few commercial spray products available), but that's usually at a lower R/inch. Until higher density PU foams are all blown with something less damaging on a full lifecycle basis they won't exactly be in the "greener than EPS" part of the material spectrum, not even close. (Open cell polyurethane surely IS greener than EPS, but not suitable for ICFs.)