ADVANCING THE FIRE PERFORMANCE OF SANDWICH PANELS

Prefabricated buildings often require a novel design approach relative to conventional construction. Planning is a delicate balance between manufacturing and simple on-site assembly. One system that is growing in popularity is the sandwich panel owing to credentials including high-strength, durable, thermally efficient and rapidly assembled. Common applications for sandwich panels include walls, floors and roof cassettes. Advantages of this form of construction include that embedded insulation and additional structural members typically are not required to achieve moderate spans in load-bearing elements such as floors and pitched roofs.

Several CAMPH Partners offer sandwich panels that are integral to their systems. EnviroSIP has a polymeric resin – glass-fibre skin on either side of a lightweight core including EPS. Habitech’s interlocking system includes a magnesium oxide external skin, EPS core and plywood internal skin. A new industry partner to CAMPH, Bondor manufactures sandwich panels with EPS, PIR and mineral wool cores for a variety of applications.

In order for the building to comply with building regulations, a sandwich panel will need to meet the relevant performance requirements of the National Construction Code (NCC). Many prefabricated building technologies are novel, such that deemed-to-satisfy provisions in the NCC cannot be followed. In order for a novel building technology to meet the NCC’s performance requirements, a performance solution must be followed (or a combination of deemed-to-satisfy and performance solutions). While achieving compliance with the NCC’s performance requirements for acoustic performance and structural performance may be readily demonstrated, achieving compliance with the NCC’s fire performance requirements is often more complex and requires the expertise of a fire engineer. The assessment may comprise a desktop assessment, computer modelling, laboratory testing, or a combination of all three.

Research activities at CAMPH have been advancing fire safety in prefabricated systems including structural insulated walls, floors, high performance prefabricated timber sandwich panels and entire prefabricated systems. This work has varied from material to full-scale structures, and from passive to active fire suppression solutions.

Structural insulated panels comprising two high performance composite skins and a lightweight core offer an excellent solution for a prefabricated system. This is due to the high strength-to-weight ratio, ability to manufacture large elements, and flexibility to adapt to different structural systems. Utilising high quality control available during fabrication, various materials may be incorporated into the system to achieve the required level of fire performance in buildings.  Innovative materials and technologies may be integrated into sandwich panels to achieve fire suppression.

“In order for a novel building technology to meet the NCC’s performance requirements, a performance solution must be followed (or a combination of deemed-to-satisfy and performance solutions). While achieving compliance with the NCC’s performance requirements for acoustic performance and structural performance may be readily demonstrated, achieving compliance with the NCC’s fire performance requirements is often more complex and requires the expertise of a fire engineer. The assessment may comprise a desktop assessment, computer modelling, laboratory testing, or a combination of all three.”
Dr David Heath, National Technical Manager – CAMPH and Dr Kate Nguyen, Research Fellow – CAMPH University of Melbourne.

A key consideration for the fire design of prefabricated structures lies in the connections between different modules and elements. Some design and assembly requirements may result in a pathway for heat and smoke to penetrate through the structure, thus fire safety must be carefully studied. Prefabricated construction often involves the use of new materials and compartmentation principles that may result in confusion among manufacturers, suppliers, designers and even fire engineers who are exposed to new construction technologies.

There are several standards that may be used to demonstrate the suitability of sandwich panels from a fire design perspective. It is clearly stated in the NCC that the combustibility of materials must be tested in accordance with AS 1530.1 (Methods for fire tests on building materials, components and structures – Combustibility test for materials). However, many products in the Australian market are imported from overseas suppliers where other standards and codes are in place that may not align with the provisions of the NCC. For example, in Europe the fire performance of construction materials is categorised into Class A to F in accordance with EN 13501 and EN 13823. The interpretation and relationship between different testings/standards is not straight forward and always requires assessment from a competent fire safety engineer. This difference frequently causes confusion in the building industry regarding the legitimation of products in Australia that have been certified to international standards.

At a system scale, two different standards are quoted from the NCC including AS 1530.4 (Methods for fire tests on building materials, components and structures – Fire-resistance test of elements on construction) and AS 5113 (Fire propagation testing and classification of external walls of buildings). The former gives the fire resistance of an element (such as a sandwich panel) counted in the form of minutes or hours. This metric measures the time that the element is expected to withstand the exposure to fire and not contribute to the spread of fire to other parts of the building. The latter falls under a performance-based solution in the NCC and specifically addresses the spread of fire on the external façade and between buildings where sandwich panels are commonly used.

The performance requirements of the NCC permit a robust assessment of fire safety that is frequently called upon during the design of prefabricated buildings. However, it is critical that a competent fire engineer is consulted during design to ensure that the required fire performance is achieved. CAMPH is working with its partners to advance their prefabricated building systems, including through fire testing, modelling and design activities. Future industry-focused events are planned at the University of Melbourne with a goal to address issues plaguing the building industry and to build an education and training program to support the Australian fire engineering fraternity.

This research was supported partially by the Australian Government through the Australian Research Council’s Industrial Transformation Training Centres funding scheme (project IC150100023). The views expressed herein are those of the authors and are not necessarily those of the Australian Government or Australian Research Council.■

“Research activities at CAMPH have been advancing fire safety in prefabricated systems including structural insulated walls, floors, high performance prefabricated timber sandwich panels and entire prefabricated systems. This work has varied from material to full-scale structures, and from passive to active fire suppression solutions.”
Dr David Heath, National Technical Manager – CAMPH and Dr Kate Nguyen, Research Fellow – CAMPH University of Melbourne.

Dr David Heath
National Technical Manager
ARC Centre for Advanced Manufacturing of Prefabricated Housing

Dr Kate Nguyen Research Fellow ARC Centre for Advanced Manufacturing of Prefabricated Housing – University of Melbourne