Polyiso Insulation Boards & Facers
Polyiso roof and wall insulation boards: long-term thermal resistance, facers, compressive strength, assembly documents and RFQ content.
Buyer summary
- What it is
- Faced rigid polyisocyanurate foam boards for roof and wall insulation. They are compared on long-term thermal resistance, facer and compressive strength.
- Main applications
- Low-slope commercial roofs (mechanically attached, adhered or ballasted), tapered roof drainage, exterior-wall continuous insulation, and cold-storage and cleanroom panels.
- Critical purchasing specifications
- Assembly: roof or wall, deck, membrane or cladding, attachment and code path
- ASTM C1289 type, class and edition
- LTTR per thickness, compared on the same basis
- Facer type and compressive strength (ASTM D1621) for loaded roofs
- Fire and wind-uplift assembly listings
- Qualification considerations
- Fire and thermal performance depend on the complete assembly and its listings. Material data alone do not establish code compliance.
- First step
- Describe the roof or wall assembly, the thickness or R target, and the code documents needed.
- How PAXOMER can assist
- Polyiso boards are compared on long-term thermal resistance, facer, compression and the assembly they enter. PAXOMER can help define the roof or wall assembly, thermal and code documentation needed, identify board or facer manufacturers with relevant evaluations, and coordinate samples. Manufacturer-level discussions on thickness, tapered layouts and volumes can follow. Manufacturer identification, qualification support and pricing discussions depend on manufacturer confirmation, specifications, quantities and terms.
Detailed technical guidance, data tables, FAQs and technical references follow below.
Building-envelope and fire-performance decisions. Thermal, moisture and fire performance depend on the complete assembly and the code path that applies. They require qualified design review and documented evidence for that assembly; material data alone do not establish compliance.
General technical information published by PAXOMER Inc. to support preliminary material evaluation. It is compiled from the sources cited on this page and has not been independently reviewed or certified by a professional engineer, laboratory or certification body. Values marked typical, illustrative or requiring confirmation are not specifications. Confirm properties, standard editions, regulatory status and suitability for your specific application with the manufacturer and, where the use is regulated or safety-related, with a qualified professional or the relevant authority.
Polyisocyanurate (polyiso, PIR) insulation board is a rigid cellular foam with facers on both faces, used in low-slope roofs, walls, continuous-insulation assemblies, cold-storage panels and specialty applications. Its thermal resistance, facer type, compressive strength, dimensional stability and fire behaviour are evaluated as part of the assembly it enters, and in North America it is commonly specified against ASTM C1289 in the United States and Canadian product standards in Canada.
This page is for roofing and envelope designers, contractors, panel manufacturers and purchasing teams preparing a polyiso inquiry. It explains how to define the assembly, why long-term thermal resistance and facer choice matter, which properties and test methods appear on data sheets, and what a useful RFQ includes. It does not state that PAXOMER stocks, manufactures or has qualified any insulation product, and its tables are a framework rather than confirmed values.
A. Product identity and terminology
1. What is polyiso insulation board?
Polyiso board is made by reacting a polyol blend with polymeric MDI in excess so that isocyanurate structures form, together with blowing agents, catalysts, surfactants and flame retardants, then laminating the rising foam between facers on a continuous line. Products include flat boards, tapered systems for roof drainage, cover-board combinations and boards for wall continuous insulation. Manufacturer literature describes flat and tapered polyiso roof insulation as a product family (S2).
2. Am I buying insulation board, a cover board or a complete system?
Clarify whether the inquiry is for insulation board alone, a high-density cover board, a tapered layout with crickets and saddles, or a manufacturer roof system with membrane, adhesives and fasteners. Each changes the documents required and who is responsible for system performance.
3. Which terms need a precise meaning?
Polyiso, PIR, PUR, LTTR, R-value, RSI, facer, coated-glass facer, foil facer, compressive strength, dimensional stability, tapered insulation, cricket, cover board, continuous insulation (ci), vapour permeance. Glossary: R-value.
B. Properties and performance
4. What does long-term thermal resistance establish?
The thermal resistance of a foam with captured blowing agent changes over time as gases diffuse. LTTR methods estimate a time-weighted thermal resistance so that products can be compared on a common basis. When comparing offers, confirm the method, the thickness and the edition of the standard used, and do not compare an initial value from one supplier with a long-term value from another.
5. How can thermal offers be compared fairly?
Ask for thermal resistance at the specified thickness, on the same basis (for example LTTR per the referenced standard), with units stated (imperial R or metric RSI). Thermal transmission measurements are often made with heat flow meter apparatus according to ASTM C518 (S4). Assembly U-values also depend on fasteners, joints and layers, so the board value is only one input.
Polyiso parameters to specify
Illustrative framework only. Values must be stated by the manufacturer for the exact product, thickness and standard edition.
| Property | Value or range | Unit | Test conditions | Test method | Grade or construction | Source | Verification status |
|---|---|---|---|---|---|---|---|
| Product standard and type or class | stated by product | n/a | Edition stated | ASTM C1289 or Canadian product standard | Board | S1 | Manufacturer confirmation required |
| Thickness and tolerance | per design | mm or in | Measured per standard | Per product standard | Board | S1 | Application-specific verification required |
| Long-term thermal resistance | stated per thickness | RSI or R | Method and edition stated | Per product standard | Board | S1 | Manufacturer confirmation required |
| Thermal transmission measurement | per method | W/(m·K) or equivalent | Mean temperature stated | ASTM C518 | Board specimen | S4 | Manufacturer confirmation required |
| Compressive strength | stated by grade | kPa or psi | Method and deformation stated | ASTM D1621 | Board | S3 | Manufacturer confirmation required |
| Facer type | stated by product | n/a | n/a | Product data | Board | S2 | Manufacturer confirmation required |
6. How are imperial R and metric RSI values converted?
Canadian documents often use metric RSI (m²·K/W) while US documents use imperial R (ft²·°F·h/Btu). One RSI equals approximately 5.678 R. Converting before comparing avoids errors when offers come from both markets. Layer thermal resistances add in series, but fasteners, joints and other layers change the assembly value, which is why the board value is only one input.
The sum applies to the boards only. An assembly calculation must account for fasteners, joints, membranes, decks and air films according to the method the project uses.
Hypothetical conversion and layering example
Hypothetical example to show the arithmetic. The board values are illustrative, not product data; use the manufacturer's stated long-term values.
| Property | Value or range | Unit | Test conditions | Test method | Grade or construction | Source | Verification status |
|---|---|---|---|---|---|---|---|
| Conversion factor | 5.678 | R per RSI | Unit definition | Arithmetic | Any board | None | Hypothetical calculation |
| Layer 1 stated value | 2.0 | RSI | Example long-term value | Input | Hypothetical board | None | Hypothetical calculation |
| Layer 2 stated value | 1.5 | RSI | Example long-term value | Input | Hypothetical board | None | Hypothetical calculation |
| Two layers in series | 3.5 | RSI | 2.0 + 1.5 | Arithmetic | Hypothetical layers | None | Hypothetical calculation |
| Same in imperial units | 19.9 | R | 3.5 × 5.678 | Arithmetic | Hypothetical layers | None | Hypothetical calculation |
7. Why does the facer matter beside the foam core?
Facers protect the foam, provide a bonding surface for adhesives and membranes, affect vapour permeance and moisture behaviour, and influence fire performance. Foil facers have low vapour permeance; coated-glass facers are common for adhered roof systems. Facer type must match the attachment method and membrane manufacturer's requirements.
8. Which compression information is useful for loaded roofs?
Compressive strength measured by ASTM D1621 for rigid cellular plastics (S3) helps compare grades for foot traffic, equipment and ballast. For heavy or concentrated loads, consider high-density cover boards or higher-strength grades and follow the roof-system manufacturer's guidance.
9. Why is material fire information different from assembly fire performance?
Fire behaviour of the board alone (for example surface-burning characteristics) does not establish the fire performance of a roof or wall assembly. Building codes in Canada and the United States require tested or listed assemblies for many applications. Ask for the assembly listings or test reports that apply to your project, and have the design professional confirm the code path.
C. Manufacturing and processing
10. How is polyiso board manufactured?
Components are metered and mixed, laid onto a moving bottom facer, rise between facers under a conveyor, cure, and are cut to length and width. Quality variables include density distribution, cell structure, facer adhesion, flatness and dimensional stability. Tapered boards are cut or produced to slope designs.
11. How should incoming inspection and trials be planned?
Check labelling, thickness, dimensions, flatness, facer integrity and damage on delivery. Retain samples by lot. For new products or suppliers, review data and run an installation trial with the specified adhesive, fasteners and membrane before full use.
12. Which problems need investigation evidence?
| Problem | Possible causes | First checks |
|---|---|---|
| Facer delamination | Moisture, adhesion between facer and foam, wind uplift | Moisture history; facer adhesion; attachment |
| Board shrinkage or gaps | Dimensional change, installation temperature | Dimensional-stability data; installation records |
| Wet insulation | Leaks, condensation, storage exposure | Moisture survey; vapour control; storage |
| Crushing under traffic | Insufficient compressive strength, no cover board | Grade; loads; cover board |
| Adhesive or membrane bond failure | Facer incompatibility, contamination, temperature | System compatibility; application conditions |
13. How should boards be stored and handled?
Store off the ground, covered with breathable protection, away from water and heat sources, following manufacturer instructions. Protect edges and facers. Do not install wet boards. Bundles can be affected by wind on roofs; secure them.
D. Applications and qualification
14. Where is polyiso used?
Low-slope commercial roofs (mechanically attached, adhered or ballasted systems), tapered roof drainage, exterior wall continuous insulation, below-grade or interior applications where permitted, cold-storage and cleanroom panels, and specialty boards with integrated cover layers.
15. Which Canadian requirements apply?
Canadian projects reference Canadian product standards and the National Building Code of Canada or provincial codes. Ask manufacturers which Canadian standard and classification a product meets, and request the evaluation or listing documents that the authority having jurisdiction will review. This page does not determine code compliance.
16. How should a buyer select a candidate product?
- Describe the assembly, substrate, membrane or cladding, attachment and climate.
- State thermal target, thickness limits, slope design and loads.
- State fire, wind-uplift and code requirements and the documents needed.
- Ask manufacturers to propose products with the product standard, type or class, LTTR and assembly listings.
- Confirm compatibility with the membrane and adhesive system before ordering.
17. Which documents should be requested?
Product data sheet naming the standard, type or class and edition; LTTR statement per thickness; compressive-strength and dimensional-stability data; facer description; fire and wind-uplift assembly listings; evaluation reports for the target market; installation instructions; and storage guidance.
E. Procurement, comparisons and decisions
18. How does polyiso compare with other rigid insulation boards?
| Board type | Where it may be preferred | Trade-offs to evaluate |
|---|---|---|
| Polyiso | High thermal resistance per thickness in roofs and walls | Long-term thermal basis, temperature effects, facer compatibility |
| Extruded polystyrene (XPS) | Below-grade and moisture-exposed uses, compressive strength | Blowing-agent changes, temperature limits |
| Expanded polystyrene (EPS) | Cost, stable thermal resistance, geofoam | Lower thermal resistance per thickness |
| Mineral wool board | Non-combustible assemblies, acoustic performance | Weight, lower thermal resistance per thickness, compression |
Choose within the assembly and code path; the comparison is orientation only.
19. What determines total installed cost?
Board price per area and thickness, number of layers, tapered design, fasteners or adhesives, cover boards, labour, waste and the energy performance over the building's life. Thicker single layers may save labour but affect joint staggering and thermal bridging.
20. What should a polyiso RFQ include?
- Project type, assembly, substrate, membrane or cladding and attachment.
- Thickness or thermal target, layer layout and tapered design if any.
- Product standard, type or class and facer requirements.
- Fire, wind-uplift and code documents needed.
- Quantities by thickness, board size, delivery location and schedule.
Prepare and submit these through the RFQ brief.
21. Which manufacturer qualification questions should be asked?
Product standards and listings held; plant locations serving the project region; tapered design service; documentation for Canadian and US markets; lead times; and change notification for formulation or facer changes. PAXOMER does not confirm any manufacturer's listings on this page.
22. Which related pages should be read next?
- Guide: PIR / polyiso insulation
- Guide: Roofing membranes and underlayment
- Related page: PET spunbond roofing carriers
- Related page: Air and vapor control membranes
- Related page: Polyurethane system raw materials
Manufacturing Regions & International Supply
No country-level manufacturing evidence specific to Polyiso Insulation Boards & Facers was confirmed in the review.
If you are evaluating manufacturers abroad, list in your RFQ brief the destination market, the documents you require and the delivery terms.
Engineering and purchasing FAQs
Each answer is general technical information, not a specification or a quotation.
Can I compare R-values from two polyiso suppliers directly?
Only when the values are on the same basis, for example long-term thermal resistance per the same standard edition at the same thickness. Initial values and long-term values are not comparable.
Which facer should I choose?
It depends on the attachment method, membrane system, vapour control and fire requirements. Follow the roof or wall system manufacturer's requirements for the facer.
Does a board fire rating cover my roof assembly?
No. Assembly fire performance requires tested or listed assemblies. Ask for listings that match your deck, layers and membrane, and confirm with the design professional.
When is a cover board needed over polyiso?
Often where foot traffic, equipment, hail or adhered membranes require a tougher surface. The roof-system manufacturer's guidance and project loads decide.
Which standard applies in Canada?
Canadian projects reference Canadian product standards and codes. Ask the manufacturer which Canadian standard and classification the product meets, with evaluation documents.
Can PAXOMER help source polyiso boards?
This page does not confirm supply or listings. Send the assembly, thermal target and documentation needs, and PAXOMER will review whether a suitable manufacturer-development opportunity exists.
Technical References
References below were opened on the access date shown. A source supports only the statement it is cited for. Standards are cited by number and title from public catalogue entries; their full text was not read unless stated.
- S1. ASTM C1289: Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board. ASTM International, 2026. store.astm.org/c1289-26.html (opens in a new tab) standard catalogue · accessed 2026-10-28
Catalogue entry opened 2026-10-28 to confirm number and title; full text not read. - S2. ENRGY 3 — Flat and Tapered. Johns Manville. www.jm.com/en/commercial-roofing/roofing-insulation-and-cover--boards/enrgy-3-in (opens in a new tab) manufacturer literature · accessed 2026-10-28
Product page opened 2026-10-28 to confirm title; cited for the existence of flat and tapered polyiso roof insulation. Not an endorsement. - S3. ASTM D1621: Standard Test Method for Compressive Properties of Rigid Cellular Plastics. ASTM International. store.astm.org/standards/d1621 (opens in a new tab) standard catalogue · accessed 2026-10-28
Catalogue entry opened 2026-10-28 to confirm number and title; full text not read. - S4. ASTM C518: Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus. ASTM International. store.astm.org/standards/c518 (opens in a new tab) standard catalogue · accessed 2026-10-28
Catalogue entry opened 2026-10-28 to confirm number and title; full text not read. - S5. PIR / polyiso insulation (PAXOMER guide). PAXOMER Inc., 2026-10-28. /products/pir-polyiso-insulation/ technical literature · accessed 2026-10-28
PAXOMER’s own guide; not an external source and not independently reviewed.
Evidence notes and limitations
What the information on this page does not establish. Confirm these points with the manufacturer, the current standard or the relevant authority before relying on them.
- Standards are cited by number and title; scopes, classifications and editions were not read.
- Canadian product standards for polyiso are referred to generically; their numbers and editions were not checked for this page.
- The description of LTTR is general; the method details in the referenced standards were not read.
- Board-type comparisons are general tendencies and not supported line by line by a recorded source.
- This page has not been independently technically reviewed or certified.
Facts checked against the cited sources
- Titles of ASTM C1289 (2026 catalogue entry), D1621 and C518 were confirmed on the ASTM catalogue on 2026-10-28.
- The Johns Manville flat and tapered polyiso page was confirmed to exist on 2026-10-28.
- The unit conversion example (3.5 RSI × 5.678 = R-19.9) was checked.
Where this connects to the full guide
The primary technical guide behind this page is PIR / Polyiso Insulation: Board, Facer & Assembly Selection. All its topics are indexed below.
Topics in the full guide
- Quick answer
- Am I buying insulation board, a cover board or a complete panel?
- Which requirements should be fixed before asking for a price?
- How should PIR, PUR and polyiso descriptions be interpreted?
- What does LTTR establish, and what must a thermal quotation state?
- How can two thermal offers be compared without inventing a target?
- Why does the facer matter beside the foam core?
- Which compression information is useful for a loaded roof or panel?
- How should board, cover board and sandwich-panel options be compared?
- Which standards should the purchasing record name?
See all 86 topics in the guide
Related guides, comparisons and tools
- PIR / Polyiso Insulation: Board, Facer & Assembly Selection Primary guide
- Roofing Membranes & Underlayment
Glossary: Adhesion · Air barrier · ASTM C1289 · CAN/ULC · Compressive strength · Density · Dimensional stability · Dimensional tolerance · EPDM · Facer
Tools: Product Finder (Roofing membranes and underlayment) · Solution Finder (Membrane performance in a wall or roof) · Manufacturer Finder
How can I submit an inquiry?
Describe your application, the specifications above and the qualification stage. The material and this page are carried into the form for you. PAXOMER replies by email; the form does not confirm stock, representation or qualification.