Is FOAMULAR NGX worth it over cheaper EPS board?

Yes if moisture is a concern. XPS absorbs less water than EPS and holds its R-value better in damp basements and foundations. EPS is cheaper per square foot if the space stays dry.

How much R-value does one board give?

At R-5 per inch, a 2-inch board is about R-10, and the 4x8 ft panel covers 32 sq ft. Check the board thickness printed on the panel, since NGX comes in several thicknesses.

Can I leave it exposed in a basement?

No. Unfaced foam needs a code-approved thermal barrier, such as drywall, over it in occupied interior spaces. It is fine behind finished walls or as exterior sheathing.

No. It is not rated for sound transmission and has no soundproofing properties. Use mineral wool or a dedicated acoustic product if noise is the problem.

What is the maximum temperature it can take?

The max service temperature is 165°F (74°C). Keep it away from recessed lights, flues and other hot surfaces.

When is the price lowest?

Rigid foam tends to dip in fall and winter, outside the spring and summer building rush. At $24.09 at SalesPort as of November 4, 2026, compare per-square-foot cost across the three stores before buying in bulk.

Owens Corning FOAMULAR NGX XPS Rigid Foam Insulation Board

Q: Where is the Owens Corning FOAMULAR NGX XPS Rigid Foam Insulation Board cheapest?

At SalesPort, for $24.09, 59% under what the other stores charge, as of our latest check.

Q: Where can I buy the Owens Corning FOAMULAR NGX XPS Rigid Foam Insulation Board?

3 stores we checked sell it, including SalesPort, Cloverdale Building Supplies, Go Build Supply & More.

Best price now

$24.09at SalesPortObserved at 3:33 PM

59% under what the other stores charge

Compared across 3 stores. Prices are checked against each store and labelled with when.

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Our take on the Owens Corning FOAMULAR NGX XPS Rigid Foam Insulation Board

FOAMULAR NGX is Owens Corning's extruded polystyrene rigid foam board, sold here as a 2-inch-thick, 4x8 ft panel (32 sq ft) rated R-5 per inch, so about R-10 per board. It is closed-cell, unfaced, mildew resistant and slows water vapor at 1.5 perms, which suits walls, attics, basements and foundations. The best new price is $24.09 at SalesPort as of November 4, 2026, with three stores listing it new.