Expanded polystyrene (EPS) roof insulation has been used in new installation and remodeling projects for over 35 years. With the capability to be used in virtually all commercial roofing systems, the closed cell, lightweight, foam plastic insulation EPS is a popular choice. EPS is most successful when installed correctly and can be used in modified bitumen systems, built up roofing, and single‐ply membrane systems that are ballasted, mechanically fastened or fully adhered.
Testing Codes & Standards
EPS insulation is recognized by all major code approval agencies and testing organizations in North America. EPS insulation manufacturers in the United States and Canada maintain numerous listings at Factory Mutual (FM), Underwriters Laboratory (UL), Underwriters Laboratory of Canada (ULC) and the International Code Council Evaluation Service (ICC‐ES).
EPS Insulation Properties
EPS insulation meets the requirements of:
- ASTM C578
- Specifications for Rigid, Cellular Polystyrene Thermal Insulation and CAN/ULC‐S701
- Standard for Thermal Insulation, Polystyrene Boards and Pipe
- Material standards that cover the types, physical properties and dimensions of cellular polystyrene intended for use as thermal insulation in the United States and Canada, provides properties for seven EPS “types” and CAN|ULC‐701 provides properties for three EPS “types.”
Because of the high standards of our EPS insulation, ASTM manufacturers are able to offer many products with compressive resistance to meet the specifications of almost any roofing project. The compressive stress and strain characteristics of out EPS insulation are determined by:
- ASTM D1621,
- Standard Test Method for Compressive Properties of Rigid Cellular Plastics (ASTM C165)
- Standard TestMethod for Measuring Compressive Properties of Thermal Insulations.
The resistance of EPS insulation and building products increases as density increases. EPS has a compressive resistance between 10 ‐ 60 psi for most construction applications. Within that range EPS can be produced to meet specific strength requirements.
Benefits of EPS Roofing
- Consistent over life of roof
- Measurable energy savings
- Lower cost per R‐value than many other insulation products
- Design flexibility and versatility in meeting project specific applications
- Compatible with fully adhered, ballasted or mechanically fastened systems
- Compatible with common roof assembly components
- Dimensional stabilityMoisture resistance
- Compressive strength
- Recycled EPS incorporated in many insulation products
- Never manufacturer with ozone‐depleting gases, such as CFCs or HCFCs
- Lightweight, less material required to meet R‐value standards
International Building Code & National Building Code of Canada
EPS insulation meets the requirements of the International Building Code (IBC). According to IBC Section 2603 Foam Plastic Insulation, for roofing applications foam plastic insulation must be separated from the interior of the building by a thermal barrier consisting of 0.5” (12.7 mm) gypsum board or wood structural panel sheathing not less than 0.47” (11/9 mm) thick. The National Building Code of Canada (NBC) requirements are somewhat different. Article 220.127.116.11.1 of the NBC addresses the use of EPS insulation in metal roof deck assemblies that form part of buildings required to be of non‐combustible construction. This Article indicates that EPS manufacturers must demonstrate that the insulation component in a metal roof assembly has been tested as a component in a roof assembly complying with the conditions of acceptance in CAN/ULC‐S126‐M. However, the requirement to demonstrate compliance with CAN/ULCS126‐M is waived if any of the following requirements included in NBC Sentence 18.104.22.168.(2) are met for the roof assembly:
- A 12.7‐mm (1/2‐in.) gypsum board or other thermal barrier meeting the requirements of CAN/ULC‐S124‐M is located on the underside of the foam plastic insulation.
- The building is sprinklered throughout.
- The roof assembly has a fire‐resistance rating of not less than 45 minutes.
In other words, the Canadian code allows EPS direct to deck application when a sprinkler system is installed under the metal deck. Since this is a common practice in commercial construction, EPS insulation can be used without a thermal barrier in many projects. Separate to the above thermal barrier requirements, both the IBC and NBC require that roof covering on roof assemblies that incorporate EPS insulation must be classified as part of a Class A, B or C roof assembly. Fire‐resistance classifications A, B and C relate to exterior fire exposure and are intended to represent different levels of fire resistance performance. They are defined by ANSI/UL 790, ASTM E108 and CAN/ULCS107 as follows:
- Class A roof coverings are not readily flammable, are effective against severe fire exposures, and do not carry or communicate (i.e., spread) fire.
- Class B roof coverings are not readily flammable, are effective against moderate fire exposures, and do not readily carry or communicate fire.
- Class C roof coverings are not readily flammable, are effective against light fire exposures, and do not readily carry or communicate fire.
Factory Mutual testing protocol, FM 4450, Approval Standard for Class 1 Insulated Steel Deck Roofs, assesses the flame spread of an interior fire on the underside of the roof deck assembly. Recognized by U.S. and Canadian code organizations, FM 4450 covers fire, wind uplift, live load resistances, corrosion of metal parts and fatigue of plastic parts. The standard applies to the assembling and performance of all components of an insulated steel deck roof. Assemblies that pass FM 4450 are given a FM Class 1 rating. Those that don’t are rated Class 2. It is important to make a distinction between what FM defines as an “acceptance” and an “approval”. An “acceptance” refers to installation in a specific project and means the product must be evaluated on a case by case basis while an “approval” of a product applies to multiple products
Underwriters Laboratory (UL)
Underwriters Lab’s test protocol UL 1256, Fire Test of Roof Deck Constructions, examines the behavior of roof deck assemblies. EPS insulation has been tested in accordance with UL 1256 and is listed as part of UL fire classified roof deck Construction #458. A separate standard, UL 580, Test for Uplift Resistance of Roof Assemblies, is used to evaluate the comparative resistance of roof assemblies to positive and negative pressures associated with wind uplift. When a product obtains UL certification, it is appropriately labeled as UL‐listed or UL‐classified.
Regulatory & Test Organizations
ASTM International Canadian General Standards Board (CGSB) Canadian Standards Association (CSA)
ASTM, CGSB, and CSA develop voluntary standards that provide minimum performance standards, test methods and evaluation criteria for building products including components used in roofing assemblies.
Underwriters Laboratories (UL) Underwriters Laboratories Canada (ULC)
UL identifies standards and performs tests necessary to establish ratings for roof assemblies, i.e. ability to meet building code requirement in both countries.
Factory Mutual Global (FM Global)
Similar to UL, FM Global is a commercial and industrial property insurance and risk management organization specializing in property protection. FM Research is its testing and evaluation resource for roofing materials.
International Code Council (ICC)
ICC, a membership association dedicated to building safety and fire prevention, develops codes used to construct residential and commercial buildings, including homes and school. ICC provides a single forum for the highest quality national and international codes and standards.
From: EPS Industry Alliance