Quick Answer: Rigid insulation board typically runs $0.50 to $4.50 per SF as of 2026, with the bulk of work landing between $1 and $3 per SF once you pick a type and thickness. Prices move with the plastic resin index, your region, and the R value you specify, so treat the range as a working estimate and pull live quotes for the bid date.
What Drives the Price
Four levers set the unit price on a rigid board bid, and you should know all four before you call a supplier.
- Type of foam. EPS (expanded polystyrene) is the cheapest, typically $0.50 to $1.50 per SF for a 1 inch board. XPS (extruded polystyrene) sits in the middle at $1 to $3 per SF because it holds more compressive strength and a higher R per inch. Polyiso (polyisocyanurate) runs $1.50 to $4.50 per SF for foil faced board and is the default under commercial roof membranes.
- Thickness and R value. Board ships in half inch through 4 inch thicknesses. A 2 inch XPS board is roughly double the 1 inch price, not 1.5x, because the facing and cutting cost is fixed per sheet. Specify by R value, not thickness, since polyiso gives about R 6 per inch while EPS gives R 3.8 per inch.
- Commodity resin index. Polystyrene and polyurethane feedstock track crude oil and natural gas. A 15 percent swing in the resin index between bid and buy can wipe your margin. Lock quotes for 30 to 60 days on any bid over 60 days out.
- Facing and grade. Foil faced, fiberglass mat faced, and HD poly faced board adds $0.25 to $0.75 per SF. High compressive grades for under slab or plaza deck use cost more than wall sheathing grades.
Typical Price Ranges by Type
Use these ranges as a 2026 reference for full truckload quantities in most US markets. Smaller orders and coastal markets trend higher.
- EPS, 1 inch, R 3.8: $0.50 to $1.25 per SF. Best for protected membrane roofs and below grade perimeter insulation.
- XPS, 1 inch, R 5: $1.00 to $2.00 per SF. The default for under slab and continuous wall insulation.
- XPS, 2 inch, R 10: $2.00 to $3.50 per SF. Common under slab in cold climate zones 5 and 6.
- Polyiso, 1 inch, R 6: $1.25 to $2.50 per SF. The standard commercial roof insulation.
- Polyiso, 2 inch, foil faced, R 12: $2.50 to $4.50 per SF. High end roof assemblies.
- Mineral wool rigid board, 1 inch: $1.50 to $3.00 per SF. Specified for fire rated assemblies where foam is not allowed.
How to Calculate the Quantity You Need
Take continuous insulation off the wall or roof area by R value, not by board count. Measure the gross insulated area in square feet, deduct openings over 16 SF, and group by thickness because each thickness is a separate buy.
For walls, take the exterior wall gross area minus windows and doors, then split by the R value the assembly calls for. For roofs, take the deck area in SF and round to the nearest bundle. A standard polyiso roof board is 4 by 8 feet, 32 SF per sheet, 20 sheets per pallet.
Apply a 10 percent waste factor on walls and a 5 percent waste factor on roofs. Wall board gets cut around windows, doors, and corners, so waste runs higher. Roof board is mostly field sheets with limited cutting, so 5 percent is enough. Round the final count up to a full pallet. Suppliers will not split a pallet without a 15 to 25 percent surcharge, and the leftover board carries to the next job if you keep it dry.
How to Buy Smarter
- Quote by R value, not thickness. A 1 inch polyiso and a 1.5 inch EPS may both hit R 6, but the polyiso is cheaper per R once you factor in labor and fasteners.
- Buy in full pallets. Pallet pricing runs 10 to 20 percent under piece pricing on the same board. If you are 3 sheets short, round up to a pallet and bank the excess.
- Get three quotes on any order over 50 pallets. Distributor margins on rigid board swing 15 to 30 percent between suppliers in the same metro. The commodity is identical, the price is not.
- Lock the resin surcharge. Most suppliers quote a base price plus a resin surcharge that resets monthly. Ask for the surcharge in writing and lock it for the bid window.
- Specify faced or unfaced on the buy. Foil faced polyiso costs more but doubles as a vapor barrier, which removes a separate sheet from your wall assembly and saves labor.
Where Estimators Get It Wrong
The most common bid error is pricing board by the sheet instead of by the R value. A cheap 1 inch EPS board looks good on the unit price until the assembly needs R 20 and you are stacking five sheets instead of three polyiso boards. The unit price is lower, the installed cost is higher.
The second error is ignoring the fastener and adhesive layer. Rigid board on a roof needs plates and screws or a full adhesive pour, and that line runs $0.40 to $1.00 per SF on top of the board price. If you price the board alone, the roof bid will be light.
The third error is underestimating waste on complex walls. A house with 12 corners, dormers, and a rake wall can run 18 percent waste, not 10. Track actual waste by trade and feed it back into the next bid. The fourth error is letting the supplier substitute without checking the R value. A "comparable" substitution often drops the R per inch by 10 to 15 percent, and your assembly no longer meets energy code.
Putting It Together
Build the rigid board line item from the assembly out: confirm the R value, pick the type that meets fire and compressive needs, take the area by trade, apply a 5 to 10 percent waste factor, round to pallets, and quote three suppliers for the bid date. Carry the resin surcharge as a separate line so a market move does not eat the margin. Get the quotes in writing, lock them for the bid window, and tie every quantity back to the takeoff sheet. That is what makes a rigid board bid defensible when the supplier invoice comes in.