Polyiso, short for polyisocyanurate, is a rigid foam board with a closed-cell core and facers on both sides. It is used above the deck under built-up, modified bitumen, single-ply and metal panel roofs.
Polyiso Roof Insulation
More R-value in less depth for commercial roofs
Polyiso (polyisocyanurate) is a rigid foam board with a closed-cell core and facers on both sides. It gives more R-value per inch than EPS, which helps on roofs where depth is limited. Source Mountain Supply can quote polyiso roof boards and tapered panels for commercial and industrial roofs.
Ask us to quote the boards in the data sheets below, including Atlas ACFoam-II and Rmax Multi-Max FA-3. Still deciding between foams? Our EPS vs. XPS vs. polyiso guide compares them, and you can see our EPS roof insulation too.
What Polyiso Roof Boards Offer
More R-value per inch
Flat polyiso boards run from R-5.7 at 1 inch to R-26.8 at 4.5 inches, measured as long-term thermal resistance (LTTR).
Facers on both sides
Glass-fiber or fiber-reinforced facers give the roof membrane a continuous, suitable surface.
Flat and tapered
Boards come in 4 × 8 foot and 4 × 4 foot sheets, plus tapered panels for slope-to-drain roofs.
Polyiso Specifications
Long-term thermal resistance (LTTR) and typical properties from the Rmax Multi-Max FA-3 and Atlas ACFoam-II data sheets.
Flat polyiso boards: R-value and packaging (Rmax Multi-Max FA-3, 4 ft × 8 ft)
| Thickness (in) | LTTR R-value | Pieces per bundle | Square feet per bundle |
|---|---|---|---|
| 1.50 | 8.6 | 32 | 1,024 |
| 1.75 | 10.0 | 27 | 864 |
| 2.00 | 11.4 | 24 | 768 |
| 2.50 | 14.4 | 19 | 608 |
| 2.60 | 15.0 | 18 | 576 |
| 3.00 | 17.4 | 16 | 512 |
| 3.10 | 18.0 | 15 | 480 |
| 3.50 | 20.5 | 13 | 416 |
| 4.00 | 23.6 | 12 | 384 |
| 4.25 | 25.2 | 11 | 352 |
| 4.50 | 26.8 | 10 | 320 |
LTTR is determined per CAN/ULC-S770 and predicts a 15-year, time-weighted average.
Typical physical properties
| Property | Multi-Max FA-3 | ACFoam-II |
|---|---|---|
| Compressive strength | 20 psi (25 psi on request) | 20 or 25 psi |
| Nominal density | 2.0 pcf | 2.0 pcf |
| Water absorption | < 1% by volume | < 1.5% |
| Dimensional stability | < 2% linear change | < 2% |
| Service temperature | 250°F max | -100°F to +250°F |
| Standard | ASTM C1289 Type II, Class 1 | ASTM C1289 Type II, Class 1, Grade 2 or 3 |
Sources: Rmax Multi-Max FA-3 and Atlas ACFoam-II product data sheets. Download the Multi-Max FA-3 data sheet and the ACFoam-II data sheet. Typical values; follow the manufacturer's installation and fastening guides.
Roof Systems Polyiso Is Used In
Built-up roofs
Polyiso boards over the deck under a built-up membrane.
Modified bitumen
A stable board for modified bitumen systems.
Single-ply membranes
Fully adhered, mechanically attached and ballasted single-ply roofs.
Metal panel roofing
Insulation under metal panel roof systems.
Polyiso or EPS? We will price both.
Tell us the R-value you need and the depth you have. We will quote the options side by side.
Polyiso Roof Insulation Questions
What is polyiso roof insulation?
How does polyiso compare with EPS on a roof?
Polyiso gives more R-value per inch. EPS usually costs less and keeps a stable R-value. Many roofs use one or the other depending on the depth available and the budget. We can price both. See the EPS vs. XPS vs. polyiso guide.
What R-values are available?
Flat polyiso boards in the Rmax data sheet range from R-8.6 at 1.5 inches to R-26.8 at 4.5 inches. The Atlas ACFoam-II data sheet lists 1 inch at R-5.7 up to 4 inches at R-23.6.
Can you quote tapered polyiso?
Yes. Atlas tapered polyiso panels come in 1/8, 1/4 and 1/2 inch per foot. See tapered roof insulation for the sizes.
What do you need for a polyiso quote?
The roof type, the R-value or thickness you need, the approximate square footage, and the delivery address. Roof plans help. Call 920-382-0382 or send a request.
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