Four Good Reasons to use Aridon

Christina Gomes & Stephen PinkneyAccording to kiwi inventor Stephen Pinkney and his partner Christina Gomes, there are four good reasons to use Aridon when building a house.

At the most fundamental level, Aridon is a new type of wall insulation made from moulded expanded polystyrene. But there’s more to this inovation.

Click here to listen to the interview in iTunes or Stitcher Radio.
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What does Aridon do?

Aridon: Insulation, building wrap, batten-cavity system and weatherproofing, all-in-one.

Aridon can perform four functions at once:

  1. It’s insulation. Aridon is rated to provide an construction R-value of 2.3. This is higher than the low code requirement of 1.9 and is due to both the very good insulating properties of polystyrene and the dramatic reduction in thermal bridging achieved when Aridon panels are installed on the outside of timber framing. 
  2. It’s a wrap. The polystyrene panels form an air barrier around the building, therefore eliminating the need for another building wrap material and restricting undesirable airflow through the wall.
  3. It’s a batten and cavity. Due to the shape of the panel, the moulded ridges take the place of battens and form a cavity inside the chosen cladding.
  4. It’s temporary weatherproofing. Aridon is approved for use as weatherproofing during a build. This means that after taking a day or two to put it up, internal work such as wiring and lining can get underway even before the final cladding is in place, potentially saving weeks on a build.

Why was Aridon Developed?

Stephen worked for 18 years as a consulting structural engineer. During that time working in New Zealand and overseas, he grew convinced that there must be a better way of doing things. Like many kiwis, Stephen was concerned about the cold, draughty, leaky houses we build and live in. Unlike a lot of others, Stephen and Christina put their concern into action to do something about it.

The Need for Speed

Prefabrication was one of Stephen’s inspirations behind the design of the product and one of the promises of prefabrication is speed.

When I spoke with Stephen and Christina, they told me that the looming mass shortage of housing, particularly in Christchurch and Auckland, was another key reason for bringing Aridon to the market. We need to build houses faster without compromising on quality and their hope is that Aridon will help achieve this.

Aridon installed
Aridon in use in Palmerston North, Humphries Construction.

Is Polystyrene Green?

I questioned Christina about the selection of polystyrene. I know many people are concerned about the environmental impact of the manufacturing process. Others are also concerned about the waterproof longevity of it.

Then there’s what to do with it after its useful life as insulation

After talking with Stephen and Christina, I’m pretty convinced that they got these issues pretty well covered. They’re certainly aware of them, and more than happy to discuss the material selection.

Check out my interview to hear more, including why it’s called ‘Aridon’!
Home Style Green

Find out More about Aridon.

The Aridon website is well written, easy to navigate and packed with information and pictures. It’s well worth checking out for more information.

Another great place to touch, feel and talk about Aridon will be at Buildnz | Designex. (Coincidently, this will also be a good place to find me next week, at the Homestar stand, so come and say hi if you’re in Auckland. I’m also presenting on stage at 2 pm on Sunday 23rd June.)


Finally,here are some of Stephen and Christina’s book recommendations.

They admitted to being avid Grand Designs fans, so definitely stock up on some Kevin McCloud DVDs and grab a copy of his book from Amazon if you haven’t already.

And here’s another great story direct from some other great kiwi entrepreneurs. Every Bastard Says No: The 42 Below Story.

Every Bastard Says No


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  • Elrond Burrell

    Interesting to find out more, but still lots of things about this that don’t convince me that it’s as good as it claims to be.

    The material itself is confused in the interview and on the product website – is it Expanded Polystyrene (EPS) or Extruded Polystyrene (XPS)? Expanded is better in many ways than Extruded but usually starts out with a lower R-value. (soem more information on the difference: High density EPS is also available but it is still expanded not extruded. This confusion makes many sections of the website unclear. We stay away from XPS if at all possible but do use EPS where appropriate or necessary.

    I don’t think the moisture issues were very well addressed in the interview nor are they on the website. There are numerous instances during construction and after where moisture might get into the wall construction and would remain trapped there by this system. There is a lot of work being done in the UK now on applying external wall insulation (EWI) for retrofits and moisture issues are key – an airtight well insulated building that traps moisture is potentially creating the same mould and other related health issues that a leaky poorly insulated building does, just in different ways!

    Maybe it is covered on the website somewhere but the detail at the slab junction, at the eaves junction and at all penetrations (windows, doors, plumbing etc) will be absolutely critical to ensure the whole system isn’t compromised!

    Hopefully it will be tested on a real build and monitored in critical locations to see how well it actually performs. (Modelling results are all well and good but predictions remain predictions!)

    Best wishes, Elrond

    • It’s Molded EPS, but as I see it, there are many questions that need answering here, just wish that they did more research before going full steam ahead with the product. As Elrond mentioned moisture is the concern here. Mixing Systems, ie. Wood and EPS, as it is with EIFs Stucco Systems, moisture is trapped and basically pressure cooks the Wood into an early decaying situation. EPS Composites have been used since the 1940s and the best outcomes are with the Polystyrene and Concrete combinations.

      Passive House is the trend forward today and this system has many faults to even start to qualify as a super insulated, airtight alternative or cladding because the cost would be prohibitive. With a few tweaks, it might be useful, but not as is.

      I’m a total EPS believer, but a lifetime of experience with aircraft, marine, RV and housing projects, I tend to be skeptical on any instant new building systems that has not been fully real-life tested.

      • mcutlerwelsh

        Elrond and Ergodesk, thanks very much for your comments. I’m interested in your suggestions to improve the system. What it was accompanied by a smart vapour barrier on this internal side?

        • An internal VB would only make it worse, these hybrid systems should only be built by Professionals, probably in factory settings with all the bugs worked out. or you will get this or…

          • mcutlerwelsh

            Looks like there’s some significant issues there. What would you recommend a professional do to ensure this doesn’t happen?

          • I could describe it for you but this video will really do the job much better job, Once you’ve start watching you will want to keep going and watch them all. It starts here with Joe describes the future of House Construction and the best example is “EPS Composite Construction.”

          • mcutlerwelsh

            Joe Lstiburek is the master. What do you think it’d take to get him on the Home Style Green podcast?

          • Thanks Elrond and Ergodesk for your comments – really great feedback and fantastic links. You will be relieved to hear our website is being overhauled to demonstrate the building science evidence behind our system, including comprehensive hygrothermal modelling and material analysis (new website launches in 2 weeks).

            Sorry for the long winded reply – it is 12 months’ worth of response!!
            ARIDON® SMART WALL was developed by structural engineers, product developers and scientists – so we understand how to design a building well, but we didn’t do a good enough job communicating the science. The philosophy behind the ARIDON® system is about raising the bar on New Zealand building practice – not to be a passive house system in isolation (yet). In New Zealand we suffer from cold houses, with terrible condensation issues and poor air quality – yet we continue to build the same way regardless of the disastrous consequences.
            Joseph Lstiburek philosophy of the Perfect Wall is the guiding principle of the ARIDON® system – start with best practice and put your rain, air, vapour and heat layers on the exterior of the building to keep the frame warm and dry.

            Here at ARIDON® we joined the four layers together – combining the ideal material (EPS shape moulded to in excess of Very High EPS
            but still vapour permeable) with interlocking, self-sealing joints between each panel, to ensure air and moisture did not penetrate through the system. This system replaces the need for building wrap, cavity battens and rigid air barriers (including extra high wind zones – tested up to 4.4kpa load as a temporary sheathing) as well as eliminating thermal bridging (minus screw penetrations = >0.1% surface area). The system has been independently hygrothermally modelled by two separate agencies – it is substantially better than all traditional NZ methods.

            ARIDON® offers a far superior, cost effective, building solution to the majority of New Zealanders. We are talking about raising the bar from wooden frames, a thin layer of building wrap and R 2.8 (or in US units, R16 ) fibreglass insulation in the cavities, with significant thermal bridging. ARIDON® is not a passive house solution (in isolation) in its current form – this is an everyday better option for 99% of the New Zealand public.
            We have one of the highest rates of asthma in the world and now we are suffering from a 2nd round of leaky homes – but this time the buildings are leaking from the inside out via condensation. The latest “fix all” solution on the market is to increase framing to 140mm, so we can insert more cavity insulation – however, this just exacerbates the thermal bridging in the corners and actually makes the outer parts of the framing cavities colder thereby increasing condensation likelihood not to mention thesignificant increase in cost and environmental impact when things go wrong.

            Continuous insulation is internationally accepted as a far superior option to dramatically reduce heat loss, aid moisture control and assist with air

            Kiwis have been building the same way for years and the
            result has a great deal of room for improvement – so it is great to have your international experience and advice feeding into educating the public. Thanks again guys

          • Some other tidbits of sage information can be gleaned from this video. Passive House has developed som very unique solutions that I will omit for now.

        • Designed right with a smart vapour barrier (I guess you’re thinking of something like Intello that will let vapour diffuse in both directions depending on conditions) it might work if the insulation layer is continuous and not bridged.

    • mcutlerwelsh

      Elrond, why do you prefer expanded (EPS) over extruded (XPS)?

  • Elrond Burrell

    I had a look through the details on the Aridon website also. I would say they do nothing to alleviate my concerns although this might be a reflection on the general state of the building industry in NZ rather than the Aridon details in particular. The trouble is the improved insulation level provided by Aridon might well exacerbate the thermal bridge, trapped moisture, airtightness, thermal continuity, breathability issues etc. Like Jon Iliffe points out in his interview on HSG there is a danger of incomplete improvements leading to problems being amplified rather than eliminated. If insulation levels are going to be dramatically improved then thermal bridging, thermal continuity, airtightness and ventilation must be equally addressed at the same time.

    Fair play to them for providing so many readily accessible details though.

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