Introduction
Expanded polystyrene (EPS) fanfold insulation is a specialized material used in roofing applications, particularly in recover and re-cover projects. It is designed to provide thermal performance, dimensional stability, and ease of installation in mechanically attached single-ply membrane systems. The use of EPS fanfold insulation is governed by a set of technical specifications, installation best practices, and compatibility requirements. These are detailed in technical bulletins and product documentation from manufacturers such as GenFlex and Insulfoam.
This article provides a detailed overview of EPS fanfold insulation, focusing on its installation procedures, material properties, and key considerations for ensuring compliance with building codes and manufacturer warranties. The information is derived exclusively from technical documentation and product specifications provided by official sources.
Technical Specifications of EPS Fanfold Insulation
EPS fanfold insulation is a rigid foam product composed of closed-cell expanded polystyrene with advanced polymeric laminate facers. It meets or exceeds the requirements outlined in ASTM C578, which standardizes the specifications for rigid, cellular polystyrene thermal insulation. The insulation is available in a "fanfold" format, meaning it is manufactured in a folded, accordion-like configuration for compact storage and transport.
To be used in warranted GenFlex roofing systems, EPS fanfold insulation must be of Type VIII and meet the following minimum physical properties:
| Property | ASTM Test Method | Minimum Requirement |
|---|---|---|
| Compressive Strength | D1621 | 13 psi (90 kPa) |
| Density (Nominal) | 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 the insulation can withstand mechanical fastening, resist water absorption, and maintain dimensional stability under various environmental conditions.
Installation Procedures for EPS Fanfold Insulation
The installation of EPS fanfold insulation involves several key steps, including site preparation, fastening techniques, and system compatibility checks. Adherence to these procedures is essential for maintaining the integrity of the roofing system and ensuring compliance with manufacturer warranties.
Site Preparation and Substrate Requirements
Before installing EPS fanfold insulation, the existing roof surface must be prepared according to the following guidelines:
- Existing Gravel Surfaces: Gravel-surfaced roofs must be cleaned using a spud and scrape method, followed by vacuuming to remove loose debris and residual materials.
- Single-Ply Membranes: If the existing roof includes a single-ply membrane (e.g., EPDM or asphalt), the membrane should be cut into 10 ft x 10 ft grids before installing the fanfold insulation.
- Damaged or Wet Components: Any damaged or wet components of the existing roofing system must be replaced prior to installation.
The fanfold insulation must never be installed directly over residual asphalt or EPDM systems if it is used in lieu of a GenFlex insulation or cover board. Additionally, the gray and tan TPO membrane should not be installed over such systems when fanfold is used.
Fastening Rates and Deck Types
The attachment rate for EPS fanfold sheathing is determined by the type of deck and the roofing system in use. For mechanically attached TPO systems (with a minimum thickness of 60 mils), the fastening rate is as follows:
| Deck Type | Minimum Fastening Rate (Per 32 sq ft) |
|---|---|
| Steel | 5 fasteners |
| Plywood/OSB/Wood Plank | 5 fasteners |
Fasteners should be GenFast #12 Insulation Fasteners or GenFast #14 Fasteners, used in conjunction with GenFlex insulation plates for secure attachment. It is important to note that InvisiWeld™ applications are not permitted when fanfold insulation is the immediate substrate.
Layout and Staggering of Fanfold Sheets
Adjacent fanfold sheets should be laid parallel to one another and staggered every 2.0 feet (0.6 meters). This staggered layout helps to minimize gaps and ensure even distribution of the insulation across the roof surface. The fanfold format allows for efficient unrolling and expansion of the insulation material during installation.
Compatibility and Performance Considerations
EPS fanfold insulation is designed for use in mechanically attached single-ply membrane systems, including TPO, PVC, EPDM, and CSPE membranes. It is particularly well-suited for re-cover applications where labor efficiency and material performance are critical factors.
Labor Efficiency and Product Advantages
One of the key advantages of EPS fanfold insulation is its labor-saving design. The material comes in 200-foot bundles and is lightweight enough that an average laborer can carry one bundle under each arm, covering a total of four squares (400 sq ft) per trip. In contrast, competing 4' x 8' rigid foam panels would require 13 sheets to cover the same area, and these would weigh nearly five times as much as a fanfold bundle.
This design significantly reduces the physical strain on workers and improves overall job-site efficiency. Additionally, the fanfold format reduces the need for on-site cutting and handling, minimizing the risk of material damage during installation.
Performance Limitations and Restrictions
While EPS fanfold insulation offers several benefits, it also has certain limitations that must be taken into account during planning and installation:
- Wind Resistance: Wind speeds up to 72 mph may be approved for projects using EPS fanfold insulation, depending on the specific characteristics of the installation. However, this approval is subject to project-specific evaluations and local building code requirements.
- Hail and Puncture Protection: Hail and cut-and-puncture protection are not available when fanfold insulation is used in place of a GenFlex insulation or cover board. This means that additional protective measures may be required in areas prone to extreme weather conditions.
- Performance Validation: For projects that require performance validation—such as those with stringent energy efficiency or durability requirements—it may be necessary to switch to a GenFlex insulation or cover board instead of using fanfold insulation.
Compatibility with Membrane Types
EPS fanfold insulation is compatible with several membrane types, including:
- TPO (Thermoplastic Polyolefin)
- PVC (Polyvinyl Chloride)
- EPDM (Ethylene Propylene Diene Monomer)
- CSPE (Chlorosulfonated Polyethylene)
However, it is important to consult local building codes and membrane manufacturers for specific system requirements. Compatibility can vary based on the membrane manufacturer’s guidelines and the intended use of the roofing system.
Code Compliance and Warranty Considerations
To ensure that EPS fanfold insulation is used in a manner that is both compliant with building codes and supported by manufacturer warranties, several key considerations must be followed:
Local Building Code Authority
Local building code authorities may have specific requirements for the use of EPS fanfold insulation, particularly in cases involving partial tear-offs or re-cover applications. It is essential to check with these authorities before beginning any installation to ensure that the proposed system meets all applicable regulations.
Warranty Requirements
EPS fanfold insulation must be installed in accordance with the manufacturer’s specifications to maintain warranty coverage. This includes proper fastening techniques, adherence to recommended fastener rates, and the use of compatible membrane types.
In some cases, the use of fanfold insulation in lieu of a GenFlex insulation or cover board may affect the warranty terms. For example, the use of fanfold insulation may void certain performance-related warranties, particularly those covering hail resistance or puncture protection.
Manufacturer Support and Technical Guidance
For any questions or concerns regarding the use of EPS fanfold insulation, it is recommended to contact the manufacturer’s regional technical coordinator. For Holcim products, this can be done by calling 800-443-4272. Technical coordinators can provide guidance on product compatibility, installation best practices, and code compliance.
Conclusion
EPS fanfold insulation is a specialized product designed for use in mechanically attached single-ply membrane roofing systems. It offers several advantages, including labor efficiency, ease of installation, and compatibility with a variety of membrane types. However, it is important to follow strict installation guidelines and consult local building codes and manufacturer specifications to ensure compliance and maintain warranty coverage.
Key considerations for installation include proper site preparation, fastening rates, layout techniques, and compatibility with membrane systems. While fanfold insulation provides significant benefits in terms of performance and efficiency, it also has certain limitations—such as the lack of hail and puncture protection—that must be addressed in the planning phase.
By following the technical guidelines provided by manufacturers and adhering to local regulations, EPS fanfold insulation can be a valuable component of a durable, high-performance roofing system.