Which is better under a concrete slab?

The NGX 250. Its 25 psi compressive strength resists the load better than the 150's 15 psi, and it keeps R-value if it gets wet.

Do they insulate the same?

Yes. Both are rated R-5 per inch, so a 2 in board of either gives about R-10. The difference is strength, moisture behavior and blowing agent, not thermal performance.

Is the NGX 250 worth the extra money?

Only for below-grade, under-slab or wet-soil jobs. For above-grade sheathing and walls, the 150 does the same insulating job for $33.35 versus $52.00 per board.

Which covers more area per board?

The 150. Its 16 in x 96 in board covers 32 sq ft; the NGX 250's 24 in x 96 in board covers 16 sq ft, so you need two NGX boards to match one 150 board.

Can I get the 150 shipped to me?

Not everywhere. The 150 cannot ship to 14 states, including California, New York, Washington, Colorado and Massachusetts. Check your state before ordering.

Which lasts longer in wet ground?

The NGX 250 is the safer bet. Owens Corning states it retains R-value after exposure to standing water and wet soil, and it has the higher compressive strength.

Owens Corning FOAMULAR 150 XPS Board vs Owens Corning FOAMULAR NGX 250

Buy the FOAMULAR 150 if you want the cheapest board for above-grade walls, sheathing or crawl spaces where 15 psi is enough. Buy the NGX 250 if the board goes under a slab, against foundation walls or into wet soil, where 25 psi and the lower-GWP blowing agent matter. The 150 is $33.35 at Home Depot as of November 7, 2026; the NGX 250 is $52.00 at MyHackerTech as of the same date. That is about $18.65 more per board for the NGX 250.

Today the Owens Corning FOAMULAR 150 XPS Board costs $18.65 less at its best price.

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