Structural insulated panels (SIPs) in Australian homes
| Construction | OSB facings bonded to an EPS core[1] |
|---|---|
| Structural role | Walls, roofs and suspended floors[1] |
| Design basis | Manufacturer design tables[1] |
| Common compliance route | CodeMark Certificate of Conformity[2] |
| Independent cost data | Not covered by sources compiled here |
| *Panel performance figures published by suppliers are commercial guidance, not independent survey data. | |
A structural insulated panel bonds oriented strand board facings to an expanded polystyrene core and forms the structure of walls, roofs and suspended floors, designed from manufacturer design tables.[1] A common way to show compliance is a CodeMark Certificate of Conformity, from a voluntary third-party certification scheme administered by the ABCB.[2] Independent cost data for SIPs is not covered by the sources compiled here.
A structural insulated panel combines the frame and the insulation into a single component. Rather than building a stud wall and then filling the gaps, a SIP wall arrives as a solid slab that is both the structure and the insulating layer. This is a different proposition from the framing materials covered elsewhere on this site, and it changes what questions matter.
What a SIP is §
An Australian SIP consists of two outer layers of oriented strand board (OSB) bonded to a core of expanded polystyrene (EPS). It functions as the structural element for walls, roofs and suspended floors, with the OSB facings carrying load[1].
Panels have sufficient strength to serve as bracing walls, although additional fixings or studs may be required where stronger bracing is needed. Internal chasings are provided so that electrical services can be run through the panels[1].
How SIPs are designed and approved §
This is the most important structural difference between SIPs and conventional framing, and it is worth understanding before comparing quotes.
Timber and steel framing have national deemed-to-satisfy standards — AS 1684 and the NASH Standard respectively — that any competent designer can work to. SIPs do not work that way. Panel design and specification rely heavily on manufacturer-provided design tables, and Australian suppliers must ensure their product complies with Australian testing standards and code requirements[1].
In practice this often means certification under the CodeMark Certification Scheme, a voluntary third-party scheme administered by the Australian Building Codes Board. CodeMark issues a Certificate of Conformity, which is one of several options for meeting the evidence-of-suitability requirements of the National Construction Code[2]. The scheme is described as best suited to innovative, higher-risk products where a manufacturer may otherwise find it difficult to satisfy NCC requirements, and achieving certification is described as time consuming and costly[3].
The practical consequence for a buyer: with a SIP home, you are not only choosing a material, you are relying on a specific manufacturer's engineering. Asking what certification the panel holds, and being able to see it, is a reasonable and specific request.
Certification of prefabricated manufacturers §
The ABCB, which administers both the National Construction Code and the CodeMark scheme, has an open consultation on a National Voluntary Certification Scheme for Manufacturers of Prefabricated Construction[4]. This would sit alongside product certification and apply to manufacturers rather than to individual products. As a consultation, it is a proposal rather than an operating scheme, and what it will finally cover is not yet settled.
Termites and moisture §
The facings of a SIP are OSB — a timber product. Australia has approximately 350 termite species, around 30 with pest status, and termites eat cellulose including timber and timber products[5]. Termite management for new building work is regulated under AS 3660.1 regardless of the structural system used[6].
The EPS core is not food for termites, but it can be tunnelled through, and a concealed core is harder to inspect than an open stud cavity. What termite management is proposed, and how the system can be inspected over time, are worth asking about specifically.
Cut edges are the other point of attention. For envelope-treated plywood, LVL, glue-laminated timber and reconstituted wood-based products, applying a brush-on preservative to cut ends is described as very important[7]. Where panels are cut — for openings, or on site — the treatment of the exposed edge matters.
What the sources do not support §
Most published information about SIP performance in Australia comes from suppliers. Claims about R-values, fire resistance levels, air-tightness and comparative energy performance are typically manufacturer-published commercial guidance rather than independent survey data, and this site does not reproduce them as established fact.
Specifically, the following are not covered by the sources compiled here:
- Comparative delivered cost of a SIP home versus a timber- or steel-framed home
- Independent measurement of in-service energy performance of Australian SIP homes
- Comparative service life
- Fire resistance levels achievable, which depend on the specific panel, cladding and assembly and are certified product by product
Where a supplier quotes a figure, the useful follow-up is to ask which certificate or test report it comes from, and whether that certificate covers the assembly being proposed for your house rather than a panel in isolation.
Summary §
| Aspect | What the sources state |
|---|---|
| Composition | OSB facings bonded to an EPS core[1] |
| Structural use | Walls, roofs and suspended floors; can act as bracing walls with additional fixings where required[1] |
| Design basis | Manufacturer design tables rather than a national framing standard[1] |
| Compliance route | CodeMark Certificate of Conformity is one accepted option[2] |
| Certification burden | Described as time consuming and costly to obtain[3] |
| Termites | AS 3660.1 management applies; OSB facings are cellulose[6][5] |
| Performance figures | Predominantly supplier-published; not independently surveyed |
Questions worth asking §
- Does this panel hold a CodeMark Certificate of Conformity or another accepted evidence of suitability, and may I see it?
- Does that certificate cover the wall assembly proposed for my house, or the panel alone?
- Who provides the structural design tables, and does an engineer certify the design for my site's wind classification?
- What termite management is proposed, and how is the system inspected over time?
- How are cut edges treated where panels are cut for openings or on site?
- If the supplier ceased trading, could another builder source compatible panels and documentation?
Sent to info@modularlivingaustralia.com.au and handled by a person. See Privacy.
References §
- WoodSolutions — Guide to structural insulated panel systems. Describes SIPS as two outer layers of oriented strand board sandwiching an expanded polystyrene core, functioning as the structural element for walls, roofs and suspended floors; states that panels have strength sufficient to be used as bracing walls though additional fixings or studs may be required for stronger bracing, that design and specification rely heavily on manufacturer-provided design tables, that internal chasings are provided for electrical services, and that Australian suppliers must ensure their product complies with Australian testing standards and code requirements. woodsolutions.com.au/applications-products/structural/structural-insulated-panel-systems-sips
- Australian Building Codes Board — Description of the CodeMark Certification Scheme — a voluntary third-party building product certification scheme administered by the ABCB, issuing a Certificate of Conformity as one of several options for meeting the evidence of suitability requirements of the National Construction Code. abcb.gov.au/about-codemark
- Australian Building Codes Board — Guidance on the CodeMark certification process. States that the scheme is best suited to innovative, higher-risk products where a manufacturer or supplier may find it difficult to satisfy NCC requirements, and that achieving certification can be time consuming and costly. abcb.gov.au/process
- Australian Building Codes Board — ABCB website. Describes the ABCB as a standards writing body responsible for the National Construction Code and the WaterMark and CodeMark certification schemes, and notes an open consultation on a National Voluntary Certification Scheme for Manufacturers of Prefabricated Construction. abcb.gov.au/
- Standards Australia — Announcement on the revision of AS 3660.2. States that Australia is home to approximately 350 termite species, around 30 of which have achieved pest status, and that termites eat cellulose including timber and timber products. standards.org.au/news/australias-termite-management-standard-revised
- Housing Industry Association — Overview of AS 3660.1:2014, which sets requirements for the design and construction of subterranean termite management systems for new buildings and new building work. hia.com.au/resources-and-advice/building-it-right/australian-standards/articles/termite-management-for-new-building-work
- Timber Preservers Association of Australia — Association FAQ. States that applying a brush-on preservative to cut ends of envelope-treated plywood, LVL, glue-laminated timber and reconstituted wood-based products is very important. tpaa.com.au/faq/
Figures are as published by the sources above at their respective dates and are paraphrased summaries, not verbatim reproductions. Verify current pricing and rules directly with builders, lenders and planning authorities.