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    Structural Insulated Panels: tracking the evolution of the 21st century building system

    Geraldine Chua

    Ancient Egyptians employed mud bricks for their homes and masonry for their grandest buildings. During the industrial revolution, cast iron rose to prominence and later paved the way for steel. From the 1950’s, concrete joined hands with Brutalism to shape multiple cities.

    And then there is the 21st century building system, the Structural Insulated Panel (SIP)– a high performance composite material defined by the US-based Structural Insulated Panel Association (SIPA) as consisting of “an insulating foam core sandwiched between two structural facings, typically oriented strand board (OSB)”. Designed for residential and lighter forms of commercial construction, SIPs are a symptom of today’s AEC industry, where engineered architecture is king.

    Although SIPs continue to gain momentum today as a preferred ‘green’ building system, structural panels were first developed over 80 years ago when the US government-established Forest Products Laboratory (FPL) constructed the first SIP home in Madison, Wisconsin in 1935. According to the Federation of American Scientists, FPL engineers had reason to believe that the structural load in walls could be replaced with plywood and hardboard sheathing, prompting the creation of prototype panels that combined framing members within the panel with insulation and structural sheathing. This led to test houses being constructed with these panels, with the prototypes later taken apart and reassembled so engineers could work out the best material combination.

    This experiment lasted three years, but a small, stressed-skin house reportedly constructed in 1937 stood until 1998, when the University of Wisconsin-Madison demolished it for a new Pharmacy School building.

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    The first Structural Insulated Panel based prefab houses developed in 1937, built for study and evaluation. Image: Inspectapedia

    Frank Lloyd Wright also had a hand to play in the evolution of the first SIP. Known for pioneering Usonian Architecture, the famed “simplicity and repose” architect had set out to create a panel with three layers of plywood, two layers of tarpaper, and no insulation that he believed would work well with the construction of highly cost-effective homes. Although the exclusion of insulation ultimately determined the demise of the Wright-type SIP, which failed to gain popularity and never made it into large-scale production, his work spurred on his student, Alden B. Dow, to redevelop the panel with an insulated core.

    Dow is generally recognised today as the first creator of the structural insulated panel, and his earliest SIPs reportedly comprised 1 5/8 inch Styrofoam cores for insulation, and 5/16 plywood facings as structural support for load bearing walls. By the 60s, rigid foam insulating products were readily available, but it was during the 90s that SIPs evolved to its current form, boosted by the advancement of computer-aided manufacturing technology that allows SIPs to be specifically fabricated out of CAD drawings in factories, then transported to site and put up in a matter of hours and days.

    THE FAST AND THE FURIOUS 

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    SIPs are easily erected either on site or in components in a factory. Image: Alpine House by Third Skin architects and Habitech systems in construction.


    SIPs are becoming a go-to option by a growing number of Australian architects and builders as it boasts to be a quicker and smarter method of construction. With the modern specifier, builder and home owner now living in a climate marked by a growing population, housing stock shortages and limited access to skilled labour, prefabricated and composite building systems are especially favoured because they not only save cost and time, but also reduce onsite day-to-day build variables to deliver a predictable, straightforward build schedule.

    Unsurprisingly, the realisation of the goodness of SIPs is a relatively new phenomenon in Australia, whose AEC industry has so far been fixated on more traditional construction methodologies. However, Bondor Australia – manufacturers of insulated composite roof and wall products such as the Insulliving building systems – believes the shift in the market is becoming more obvious.

    “Our local rising energy costs, trade shortages and labour costs are now driving demand from the general public,” Bondor’s National Product Manager for Insulliving  and Solarspan, Paul Adams, explains.

    “[People are] seeking these alternative build methods to achieve for themselves a superior building environment that is more economical to construct and run, sustainable and comfortable to occupy.”

    At the heart of SIPs’ main benefits is a simplification of construction and cost – the reigning beat to which almost all elements of a project marches to. As Adams points out, SIP construction effectively removes the “numerous layers of building materials that have been introduced over the years in an attempt to satisfy necessary building compliance, such as thermal or fire performance”. In the real world, this translates to an ability to more easily resolve design issues despite being subjected to tight budget constraints. For instance, with insulation already integrated into the structure, less money will need to be spent on additional insulation initiatives within a home or office. These savings can either stay in the clients’ pockets, or be spent on other design features.

    Sustainability credentials is another key advantage of SIPs. According to the director of Melbourne-based architecture firm Atelier Red+Black, Michael Smith, who is hoping to use SIPs on a new project he is working on, he was attracted to the system as it promised a 7-8 Star energy rating, and an R4 insulation rating from the outset. Western Australian architect Andrew T Boyne, who used SIP panels for all the walls, floors and roof of the completed Augusta Beach House, also said the use of SIPs helped him “create a building that was built of insulating foam like a huge esky”, which is a more interesting way of saying “ESD alert!”.

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    An exercise in lightweight construction, The Augusta Beach House utilises SIPS panels as the structure for walls, floor and roof. SIP panels, says Boyne, ensure that the structure is very rigid, has great insulating properties and is easy to transport and install.


    And then there is builder Tenheggeler Homes, who will complete Central Queensland’s first Eco Cool Home display home in August 2016. Made of Bondor Insulliving wall panels and a Solar Span roof, the display home has already achieved a 9.1 star rating, attained up to a C2 cyclone rating, with a constant temperature expected to be maintained within the home once completed. Lock-up times are also expected to be reached in a mere two to three weeks, Troy and Greta Tenheggeler say.

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    The Bondor Insulliving home under construction.

    Contributing to this green badge is the use of fewer joints in SIPs, which means a tighter building assembly. In fact, a study by the largest US Department of Energy, Science and Energy laboratory, Oak Ridge National Laboratories (ORNL), found that a SIP-constructed home was considerably more airtight than a wood-framed and fiberglass-insulated room when subjected to identical climate conditions and a blower door test.

    Bondor’s Paul Adams, who isn’t working with either Smith or Boyne on their projects, tells us a similar story of the green goodness of composite systems:

    “Composite insulated steel products address deficiencies in energy efficiency by creating a continuous thermal barrier around the home. This reduces heating and cooling loss caused by air leakage and thermal transfer resulting in up to a 40 per cent reduction in energy costs for the home owner.”

    If savings and prefab are two words that won’t entice you, perhaps ‘waste’ might. Since SIPs are pre-engineered, any waste produced during manufacture is minimised. Being produced in a controlled environment also reduces delays associated with weather changes that may be more common for traditionally constructed projects.

    BUT HOW DOES IT ACTUALLY WORK?

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    Alpine House by Third Skin architects and Habitech Systems uses a SIP building system that was refined for local conditions.


    Although the manufacturers of SIPs will shout themselves from the rooftops, the truth is that SIP use will require a re-learning of the construction process, especially for architects and builders who new to the system. According to Adams, a SIP-constructed project typically starts with architects, building designers and builders advocating the use of SIPs to their clients with the pitch that it is a faster build process that leads to a home which is more cost-effective and environmentally friendly.

    Easy enough.

    But the next step doesn’t come as naturally, and differs from project to project. Bondor recommends that architects create a set of plans as per a normal house design, typically with an architectural skillion or gable style roof. It is also not rare for architects to adapt the existing plans and designs already created by SIP manufacturers, with little change made to their drawings other than modifying wall thickness. This leaves the actual layout of panels to the manufacturer and their shop drawers. However, there are architects like Boyne who believe it is important to “use the material to its maximum”, and choose to layout each panel in their plans.

    “[Doing so for the Augusta Beach House] required a separate set of plans, elevations and details that described how the SIPs panels would be installed,” he says. “There were a number of unique details in the house that differed from the details supplied by the manufacturer and there are some significant engineering achievements. The panel design was ultimately a collaboration between the builder, the manufacturer, architect and engineer.”

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    The Augusta Beach House was constructed in a boat building factory in Perth and then trucked in three complete pieces to its site three and a half hours drive away.


    As with all build projects, engineering and council approval must be acquired before any significant work can proceed. In this case, build and design teams will place an order with a SIPs manufacturing facility once given the green light, before waiting a few weeks for the panels to arrive on site.

    It is at this stage that experience and expertise – and therefore problems – are truly revealed. The delivery of SIPs, in the form of flat packs consisting of the walling and roofing panels, should arrive on site based on the installation sequence nominated by builders. If the panels are supplied, labelled and installed to the correct sequence, the building structure should go up fairly quickly – the Augusta Beach House’s SIP enclosure was completed in approximately two weeks. Moreover, correct SIP delivery and installation also reduces time, logistics and space requirements for storing multiple building materials onsite, including framing, bricks pallets, plasterboard, or other cladding products.

    Any challenges faced onsite are typically a product of earlier issues; when mistakes were made on paper and to shop drawings, or if the design intent was not accurately communicated to the engineers. Failure of thorough coordination can also be the downfall of a prefab project, as you can imagine what happens if the wrong panels are manufactured and arrive first, or worse, if the wrong SIPs are installed first.

    However, Boyne assures that SIPs aren’t as challenging as most assume, and can be “easily worked with conventional tools.”

    “Any problem can be overcome with a saw,” the WA architect says. “SIPS do provide conduit holes, but sometimes it was necessary to chase services by cutting into the panel – this was easy enough to do.

    “Vertical conduit holes can be created by dropping heated ball bearings through the panel to eliminate chasing, but ball bearings of the required size can be hard to find. We found some in the workshop of a machinist,” he adds.

    GUIDE FOR SIPs VIRGINS

    • Confirm with your SIP supplier the origin of your materials
    • Check for written certification that the materials used have been physically tested and engineered according to Australian Standards
    • Do not worry about it being a one-time only offer – most SIP-constructed buildings can be renovated and adapted down the road. 

     

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