Skip to content
Carlisle SynTec InsulBase 0.5 in. 4 ft x 8 ft Grade-II (20 psi) Polyiso Roof Insulation
Regular price $22.30Orders start at $399 — combine any items to reach the minimum. Learn more
Carlisle SynTec InsulBase 0.5 in. 4 ft x 8 ft Grade-II (20 psi) Polyiso Roof Insulation
Carlisle SynTec InsulBase Grade-II rigid polyisocyanurate roof insulation board, 0.5 in. thick and 4 ft x 8 ft, rated 20 psi. A closed-cell polyiso core is bonded to glass-reinforced felt facers, with a dark GRF side for ReadyFlash adhesive control. Pairs with Carlisle single-ply membrane systems.
Key Features:
- Rigid polyiso core: Closed-cell polyisocyanurate foam core bonded on each side to glass-reinforced felt facers.
- ReadyFlash technology: Dark GRF on one side and light GRF on the other lets contractors control membrane adhesive flash-off times.
- 20 psi compressive strength: Grade-II (20 psi) board for standard low-slope roof assemblies.
- High R per inch: Polyiso provides the highest R-value per inch of commercially available insulation products.
- Steel deck approved: Approved for direct application to steel decks.
- Eco-friendly formulation: Zero ozone-depleting components; HFC- and HCFC-free formulation.
- Broad approvals: ASTM C1289 Type II Class 1 Grade 2; FM Class 1; UL Classified; IBC 2603; Florida Building Code approved.
Specifications Table:
| Specification | Details |
|---|---|
| Brand | Carlisle SynTec |
| Manufacturer model | 323589 |
| Sell unit | 1 board, 0.5 in. x 4 ft x 8 ft |
| Product line | InsulBase |
| Material | Polyisocyanurate (polyiso) foam with glass-reinforced felt (GRF) facers |
| Color | Tan |
| Dimensions | 4 ft x 8 ft, 0.5 in. thick |
| Thickness | 0.5 in. |
| Coverage per unit | 32 sq ft per board |
| Compressive strength | 20 psi (Grade II) |
| Standard | ASTM C1289, Type II, Class 1, Grade 2 |
| Approvals | IBC Section 2603; UL 790; UL 263; UL 1256; FM 4450/4470 Class 1; Title 24; PIMA Quality Mark; CAN/ULC S704 Type 2 & 3 Class 3; Florida Building Code; CDPH Compliant; UL Classified; LEED |
| Weight | 5.7 lb per board |
| Intended use | Low-slope commercial roof insulation under membrane |
Coverage & How Much You Need:
Each 4 ft x 8 ft board covers 32 sq ft of roof deck. Divide the roof area by 32 sq ft per board; roughly 3.2 boards per roof square before cutting waste, sold individually.
Fit and Compatibility:
Designed for Carlisle low-slope roofing systems under Carlisle single-ply membranes (EPDM, TPO) with Carlisle adhesives and fasteners. ReadyFlash GRF facers let you choose which side receives membrane adhesives; membrane, adhesives and fastening plates sold separately.
Frequently Asked Questions (FAQ):
Q: What is included?
A: One 0.5 in. x 4 ft x 8 ft InsulBase Grade-II (20 psi) polyiso board; sold per piece.
Q: How many boards cover a square (100 sq ft)?
A: Each board covers 32 sq ft, so a roof square requires about 3.2 boards plus cutting waste.
Q: What is ReadyFlash?
A: The board has dark GRF on one side and light GRF on the other, letting the contractor choose which side receives membrane adhesive to manage flash-off times.
Q: Can it go directly on a steel deck?
A: Yes, InsulBase is approved for direct application to steel decks.
Q: What standards does it meet?
A: ASTM C1289 Type II Class 1 Grade 2, plus UL 790/263/1256, FM 4450/4470 Class 1, IBC 2603 and Florida Building Code approvals.
Q: What is the compressive strength?
A: This Grade-II board is rated 20 psi.
Expert Verdict — Reviewed by the SuperArbor Pro Desk
The 4 ft x 8 ft format covers more area with fewer seams than 4x4 boards, speeding installation on open decks. Layer 0.5 in. boards to reach the assembly R-value called out by the project design. Follow the roof assembly specification for attachment and confirm the chosen side for membrane adhesive using ReadyFlash.
Follow the roof assembly design, manufacturer installation instructions and local building codes; use proper roof-edge fall protection when working on low-slope roofs.
Order Carlisle SynTec InsulBase 0.5 in. 4 ft x 8 ft polyiso boards for efficient low-slope roof insulation.
All third party trademarks, including logos and icons, referenced on our website and product pages remain the property of their respective owners. Unless specifically identified as such, Arbor's use of third party trademarks does not indicate any relationship, affiliation, sponsorship, or endorsement between Arbor Home and the owners of these trademarks. Any references by Arbor Home to third party trademarks are to identify the corresponding third party goods.
