The What:
Structurally Insulated Panels (SIPs) are a relatively new method of construction. Popular for some time in the U.S. these panels can be used to build walls, floors and roofs but the term ‘SIP’s’ describes a sort of hybrid technology. They are a ‘unitised’ building block which fall within the broader category of a ‘sandwich’ panel. Sandwich panels have been around for a long time and are commonly used in industrial warehousing or the like to form walls and roofs of large buildings (refer Bondor & Kingspan).
Sandwich panels integrate the cladding, insulation and lining by sandwiching the insulation between the external cladding and the internal lining to make a thickly laminated panel. There are many different types of sandwich panels on the market. Typically they’re used in commercial situations like cool-rooms. Until recently in Australia their use in domestic housing was resigned to prefabricated roofing products like Tridek. However with the increasing demand for high performance housing, sandwich panels & moreover self-supporting ones, known as SIPs are increasingly being used in the residential sector and this has lead to their uptake in Australia & New Zealand.
The Why:
SIP’s have increased in popularity because of their ability to maximise the layer of seamless insulation within the building envelope and if well built should result in an air-tight interior; which in turn will translate to lower energy consumption. There are pros and cons of air-tight buildings which is worthy of further discussion but I’d like to clarify something else about SIPs which is often not explained. That is, SIPs are referred to as ’structurally’ insulated panels (not ‘Integrated’ btw) but the reference to ‘structural’ is easy to confuse. Sandwich panels are typically non-structural, used as a skin suspended over an external frame. Whereas SIP’s are a sort of semi-structural building unit. They are not necessarily structural in their own right but they are at minimum ‘self-supporting’; so if you were to build a box from SIPs it would stand upright but similar to a cardboard box, if you were to apply force to that box (like stepping on it with your foot) it would collapse. This means that although SIPs are used in lieu of a timber frame and although they can span large distances they also have very specific structural limitations and for this reason, beams and lintels are still required to support and carry the load across their openings.
Prior to procuring the construction of my own home using SIP’s, I spent a lot of time trying to understand how they’re best used. This journey to understand SIP’s was difficult as companies who make them ultimately want to maximise sales volume and don’t necessarily explain their limitations. Not to mention that in 2015 when I started researching SIP’s the companies selling them in Oz were mostly reselling product manufactured in the U.S. and so technical representation was ‘light on the ground’.
The How:
It is left to those of us who are designing buildings to determine the suitability of products we specify and my journey to understand SIPs started out with the concept of assembling a house from a flat-packed kit of parts but as I progressed I understood that constructing the shell would be less of an Ikea adventure and more of an expertly built precision exercise that required a highly competent builder. When I advanced to the stage of undertaking construction drawings I began to understand the implications of the term ‘structural’ [in SIP] (as I’ve described above) and how this impacted their intended use for the second floor of our house. Once I realised that the upper floor would require deep beams to support SIP’s larger floor spans, I saw that this would affect the levels of the house requiring an increased height of about 300mm (so not to compromise ceiling height below). This meant that in the house I currently occupy we have SIPs roofing and walling but no SIP’s flooring and instead we used conventional floor framing for the upper storey*.
SIPs are commonly 1200 wide with a variable number of lengths. One way to visualise your design using SIPs is to imagine printing out the architectural drawings of your project, cutting around the edge of each plan & elevation, then placing them onto a board with their edges touching. This would give you a cutting template. If you imagine that template laid over a tiled surface you can visualise the tiles as the units which make up the walls, roof, floor etc. This may be useful to understand how we determine the panels for ordering (although the whole process is vastly more complex than that).
Ready-cut is a service provided by SIPs Industries (WA) who undertake a sort of cut-to-template method. You may consider getting your panels pre-cut like this so that when they come to site they just need to be assembled and that would remove one hurdle of building with SIP’s. Be aware this process attracts a premium (although it may be equal to the labour time of cutting them on site + there are some environmental benefits of the raw materials remaining at the location of manufacture).
As a Building Designer I became determined to understand how many panels we needed to order for our house. To that end I produced a 3D modelling component which allowed me to array the panels along the building form and to schedule the required quantity and sizes of panels. I’m happy to now offer this as an additional service provided by Harmonic Design.
The Who:
SIPs are a specialist building material, trade & methodology. For that reason you’re best to look for people who understand them and who have experience with them. For those reasons they do attract somewhat of a premium in terms of their installation although there are some builders who will work with them directly and other builders who will employ sub contractors to install them.
Don’t expect much love from structural engineers either. Unless they’ve worked with the SIP system before they probably have no idea how they work. The subtleties of the system cannot be easily understood from installation guides or construction manuals. Insulspan have lots of details and videos online which help to guide designers and builders. Their product is exported from the U.S. as discussed further down.
Some info about various parties who I had dealings with whilst trying to procure our house in Normanville:…..
SIPS industries
In 2017 after a working with other companies we sourced the panels through these guys. They're the most cost effective that I have found and will easily give you a ‘supply only cost’ of the panels you need which will help you to budget. They offer their pre-cut design service but their price will possibly double for that. Their details are quite good although they’re not as pretty as the Insulspan one’s. You can see the use of the splines (studs) everywhere in their details which is a good representation of the built result - ie there’s still plenty of studwork required. Studs at corners, panel joins (some) window inserts (if a lintel isn’t required) + top and bottom plates, etc.
http://www.sipsindustries.com/about/downloads/
Structural Panels Australia (Associated with Tridek Roofing)
These guys were still developing their SIP’s business when I went to them initially (Seems like they expanded from Tridek). They were very helpful initially but failed to back up their sales pitch when I went looking for tech help. Having said that I would take a second look at them because they’re offering an alternative to EPS foam core which is what I was initially trying to get hold of - PUR - because it is more eco’ friendly than EPS core (read note about EPS further down).
http://structuralpanels.com.au/products/
Their tech details are quite good also but still hard to garner how the system works in reality. Eg, you can’t easily use panels as flooring if you’re doing a big span (like I have done). You practically need a post and bearer system if you’re going to do the floor with panels - still possible but you need a deeper floor section than typical - which I didn’t want so I went back to using joists for the first floor.
Fenster & Panel
These guys were very helpful for the most part but seem to want to build rather than supply. I got a lot of info from them but after they did all that they didn’t seem to want to give me a panel-only supply quotation which is probably because they were importing their panels from the U.S. at a premium. They import Insulspan panels.
http://fensterandpanel.com.au/links/
Insulspan
Insulspan’s website is fantastic and has a lot of links and general info - however if you don’t intend to become a building designer, architect or builder, I wouldn’t bother with all the technical discussion - leave it to the professionals.
http://www.insulspan.com/product_specs/product_bulletins.aspx
QikFitFloors - An alternative pre-fab flooring system:
I would honestly consider using this system (or another mob) for a ground floor install if you’re not doing a slab. I did however struggle to get a quote from them, perhaps because my project was in SA though.
http://www.qikfitfloors.com.au/wp-content/uploads/2014/03/QitFit-Instruction-Manual.pdf
The Summary:
There are various pro’s & con’s of using SIP’s as discussed on other forums. I’d suggest you cannot do too much research however I’m happy to provide a broad testimonial for SIPs and advocate their use. Not only do they have thermal benefits but like Strawbale they also have acoustic benefits and seem to provide an excellent level of resonance (in the case of our Normanville Residence I also exposed much of the OSB lining as a design feature which probably improved the acoustics). If like me you are looking for a high level of thermal comfort to be delivered by continuous insulation but aren’t in a position to use a method like Strawbale or Hempcrete, SIP’s may be an appropriate solution.
Finally, a note about EPS foam-cores within SIPs . If you’re an environmentalist (like me) you may struggle with this material. A reality of EPS is that although it’s ‘non-toxic’ it is still a troublesome pollutant. EPS has many applications in construction from slab insulation through to everything that comes to site packaged in the stuff (polystyrene). Unfortunately even if you have a tidy builder, EPS wastage from the panels being ‘worked’ onsite, off-cuts will find their way into your immediate environment. So I’d strongly advise sourcing PUR or PIR foam based panels because of the environmental dilemmas we face with EPS. Yes - we used EPS to construct our own house but I’m troubled by this. The problems associated with EPS have increased since the recycling crisis of 2016/17 which has impacted recycling streams world-wide. It is now much harder to recycle EPS in Australia than it was and this means more waste is going to land fill.
Ideally we’d all source PUR foam panels instead of EPS!
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*Adding SIPs for a floor suspended above ground also tends to increase the complexity of the build due to plumbing, waterproofing of wet areas, wiring etc.