Introduction
EPS Fanfold insulation is a specialized expanded polystyrene (EPS) sheathing material used in roofing systems to improve thermal efficiency and structural performance. When integrated into roofing applications, it serves as an insulation layer beneath single-ply membranes such as TPO, PVC, and EPDM. The provided documentation from leading manufacturers—Holcim, GenFlex, and Insulfoam—outlines specific installation procedures, performance limitations, and compatibility constraints for using EPS Fanfold in various roofing systems. This article synthesizes these instructions and technical considerations to provide a clear and actionable overview for professionals and DIY users involved in roofing projects.
Technical Overview of EPS Fanfold Insulation
EPS Fanfold insulation is a closed-cell, lightweight, and dimensionally stable insulation material that meets the requirements of ASTM C578, the standard specification for rigid, cellular polystyrene thermal insulation. The material is composed of expanded polystyrene (EPS) and features advanced polymeric laminate facers that enhance its durability and compatibility with roofing membranes.
Key physical properties for EPS Fanfold insulation, particularly Type VIII, include:
| Property | ASTM Test Method | Minimum Requirement |
|---|---|---|
| Compressive Strength | D1621 | 13 psi (90 kPa) |
| Density | C 303 | 1.25 pcf (20 kg/m³) |
| Moisture Vapor Transmission | E96 | <1 perm (<57.5 ng/(Pa·s·m²)) |
| Water Absorption | C272 | <1% by volume |
These properties ensure that EPS Fanfold can withstand mechanical stresses during installation and provide long-term insulation performance in roofing systems.
Compatibility and Usage Constraints
EPS Fanfold is permitted in certain mechanically attached roofing systems, including those using TPO, PVC, and PVC KEE membranes. However, the material has specific compatibility constraints that must be followed to ensure system integrity and warranty compliance:
- InvisiWeld™ applications are not allowed when Fanfold is the immediate substrate.
- Damaged or wet components of the existing roofing system must be replaced before installing Fanfold.
- Fanfold must have a suitable facer. “Bare” EPS must never come into direct contact with Elevate PVC or PVC KEE membranes, or with residual asphalt.
- Gray and Tan TPO membranes should not be installed over existing asphalt and EPDM systems when Fanfold is used in place of an insulation or cover board.
- Adjacent Fanfold sheets should be laid parallel and staggered every 2.0' (0.6 m) to ensure structural integrity and minimize thermal bridging.
In some cases, performance validation requires the use of an appropriate Elevate or GenFlex insulation and/or cover board instead of Fanfold. Users should consult with local building code authorities for requirements related to partial tear-offs and recovers.
Installation Procedures
Surface Preparation
Before installing EPS Fanfold, the existing roof surface must be properly prepared. The following steps are recommended:
- Gravel-surfaced roofs should be spud/scraped clean and vacuumed to remove debris and residual material.
- Existing single-ply membranes should be cut into 10 ft x 10 ft grids to facilitate secure attachment of the Fanfold.
- Any damaged or wet components of the existing roofing system must be replaced before proceeding.
Fastening Requirements
Fanfold is typically mechanically attached using specialized fasteners and plates. The recommended fastening systems include:
- Elevate #12 insulation fasteners or All-Purpose Fasteners
- Elevate Insulation Fastening Plates
- IsoFast™ #12 Belted Fasteners and Insulation Plates
- AP AccuTrac® Kits
For steel and plywood/OSB/wood plank deck types, the minimum fastening rate is 5 fasteners per 32 square feet for mechanically attached TPO membranes (minimum 60 mil thickness). This ensures proper adhesion and long-term stability of the insulation layer.
Performance and Warranty Considerations
The use of EPS Fanfold in roofing systems is subject to certain performance and warranty limitations:
- The maximum Red Shield™ Warranty term for systems including Fanfold is 20 years.
- Wind speeds up to 72 MPH may be approved based on project characteristics.
- Hail and Cut & Puncture Protection are not available when Fanfold is used in lieu of an appropriate insulation or cover board.
Users should note that these limitations may affect the overall durability and performance of the roofing system, particularly in high-wind or high-impact environments. For such applications, it is recommended to consult with the manufacturer's technical team for alternative solutions.
Staggering and Layout Techniques
Proper layout and staggering of adjacent Fanfold sheets are essential to ensure even load distribution and minimize thermal bridging. The following guidelines should be followed:
- Sheets should be laid parallel to each other.
- A staggered pattern should be used every 2.0' (0.6 m).
- This pattern helps to reduce thermal bridging and improve overall insulation performance.
Failure to follow these layout guidelines may result in reduced energy efficiency or potential system failure, particularly in large-scale installations.
Compatibility with Specific Membrane Systems
EPS Fanfold is compatible with several membrane systems, including:
- Elevate UltraPly™ TPO
- Elevate PVC
- Elevate PVC KEE
- GenFlex EZ TPO
- TPO (60-mil minimum)
- PVC
- EPDM
- CSPE membranes
However, it is important to note that Fanfold is not compatible with InvisiWeld™ applications. Additionally, Gray and Tan membranes should not be installed over asphalt or EPDM systems when Fanfold is used in lieu of an insulation or cover board.
Performance Validation and Alternative Solutions
For projects requiring performance validation, users should consider switching to an appropriate Elevate or GenFlex insulation and/or cover board. These materials offer higher performance standards and are often required for systems with extended warranties or high-performance expectations.
Users should also consult with local building code authorities to ensure compliance with partial tear-off and recover requirements, which may vary by jurisdiction. This is particularly important in retrofit or recovery applications where existing roofing materials are retained.
Contacting Technical Support
For further assistance or to confirm project-specific details, users should contact the manufacturer’s regional technical coordinator. For Holcim, this number is 800-428-4442. For GenFlex, it is 800-443-4272. These resources provide access to technical support, product specifications, and installation guidance.
Conclusion
EPS Fanfold insulation is a specialized material that can be used in certain mechanically attached roofing systems to enhance thermal performance and structural integrity. However, its use is subject to strict compatibility and installation requirements to ensure system durability, warranty compliance, and long-term performance. Users must carefully follow the outlined procedures, including surface preparation, fastening rates, sheet layout, and compatibility constraints. For high-performance or warranty-protected systems, it may be necessary to use alternative insulation or cover board materials. By adhering to these guidelines and consulting with manufacturer technical support, users can ensure the successful integration of EPS Fanfold into roofing applications.