Frequently Asked Questions (FAQs) about SIPs

What designs work with SIPs?

SIPs offer even more design flexibility than traditional stick building methods. We encourage our clients to design their build to utilise all the advantages that this premium building system offers.

Any design can work with SIPs. For larger projects, particularly commercial ones, we recommend getting our expert design support team involved early to ensure the most optimum use of the system.

How do I obtain building consent for Formance SIPs?

The Formance System is a complete pre-engineered system certified for compliance with the New Zealand Building Code under the CodeMark scheme. Designs must comply with the Formance Design Guide (there is a link to obtain this at the bottom of the page). Designs are submitted along with a copy of the guide and the designer's checklist found within the guide. 

There have been many Formance projects consented throughout New Zealand. Formance projects have been through all major councils and most of the regional councils as well so you can specify Formance with confidence.

Does the Formance system require additional engineering?

No, Formance homes do not require additional engineering input (and cost) unless the design is outside of the scope of the Design Guide. The Design Guide is pre-engineered.

What are environmental effects of choosing Formance?

The Formance system has a very good environmental pedigree. Consider the following:

  • OSB used in Formance panels comes from SFI managed forrests. 
  • OSB used in Formance panels utilises 90% of the useable timber from the source tree. Compare this to under 25% utilisation in timber framing.
  • EPS used in Formance panels is completely harmless and fully recycleable. 
  • The EPS manufacturing process (steam-expanded polystyrene beads) has a  25% smaller CO2 footprint per R value compared to fibreglass insulation.
  • Formance SIP buildings have a greatly reduced carbon footprint when compared with traditional timber framed buildings over a building lifetime.  

Choosing Formance is an environmentally responsible decision.

Do Formance SIPs come with a warranty?

Absolutely, we have a 20 year warranty on the panel manufacturer for delamination.

Who will build my Formance SIP home?

We're working with forward-thinking builders around the country to ensure high-quality installation of Formance SIP homes. To find out if there is a builder in your area visit our Find Your Builder page.

If you have a preferred builder of your own we are happy to work with them if they meet three key criteria:

  1. No compromises on QUALITY
  3. Member of either Master Builders or NZ Certified Builders

We're very happy to provide support and training to builders looking to build to a better standard with Formance SIPs. Are you a builder wanting to upgrade? Be sure to review the benefits of building with SIPs and how you can get on board.

How much do Formance SIPs cost?

Formance SIPs can be as cost-effective as conventional building methods when the panel layout and utilisation are considered in the design phase of the building. We are very happy to provide a no-obligation budget estimate through our online pricing submission tool on your concepts.

Straight material cost is almost identical to 140mm stick framing, with R3.6 batts and a RAB. The main difference between SIPs and that 140mm framing solution is the ongoing high performance from SIPs. SIPs will be performing as well in 20,30,40 plus years as when it was first installed, whereas the framed house will not only have lost its thermal performance through slumping batts and air currents (and it never performed as well in the first place) as well as this when you factor in labour costs and ongoing reduction in energy usage, the savings using Formance SIPs make the financial justification a no-brainer.

What is the best way to run services through SIPs?

We have standard holes in the EPS, 1 vertically in the centre of the panel, and two horizontally, usually at 250mm and 1000mm from the bottom of the panel. Electricians use flexible fibreglass rod to run the cables through. We also use plasticiser-resistant (purple coloured) sheathing on the electrical cable.

Plumbing is a little different, we recommend that this is put on internal framing walls where possible, and not through the EPS core.

How do you finish the walls on the inside?

The most common option for finishing the interior is to use plasterboard. Yes, we can also leave the Formance OSB SIP exposed on the interior. However, you will need to consider the black printed mill markings on the OSB. Any sheet material can be readily applied by direct fixing to the inside face of the SIP as a lining, in fact it’s very easy as the panels are so precisely straight.

But due to the strand board mill mark & irregularities of the manufacturing process, the visual appearance of panels can be inconsistent.  Formance recommends the use of either a solid colour paint or lining overlay.

Do Formance SIPs restrict my cladding options?

No, not at all. You can clad your Formance home in whatever cladding you like, subject to it meeting the requirements of the New Zealand Building Code. All SIPs require a cavity system to ensure full compliance with E2 of the code.

Are SIPs any stronger than sticks?

Er hmm, that's like saying "are planes faster than ships"! Yes, SIPs are incredibly strong, effectively providing double bracing capacity to the wall. Beside bracing SIPs have huge impact resistance both inside and out, and because they're nailed AND bonded at the joints they will be creak-free forever. Houses that get noisier over time through movement in wall and roof connections are a thing of the past; post-build structure degradation simply does not happen with a Formance SIP house.

Why aren't you using Polyurethane for Formance SIPs?

We have chosen to go with the SIP core material that has the longest track record and is used by the majority of SIP manufacturers in North America. Approximately 93% of all SIP builds are with EPS core SIPs. For NZ conditions we believe EPS is the right material choice. It is fully recyclable and completely non-toxic with none of the off-gassing associated with other types of materials.  

Thermal Performance
EPS has a stable R-value that will never drop like PUR. Polyurethane foam is typically rated with a 6-month aged value because its ability to resist the flow of thermal energy may change in the first several months after production. PUR has a higher initial R-value for SIPs, but for NZ conditions the R values of EPS are still very high, particularly when combined with the inherent air-tightness achieved by SIP construction. Airtightness trumps R-value.

EPS is easier to work with on site. Cutting PUR often produces vapours which cause irritation; EPS does not. Adding wire chases and other site-work can be performed more readily with EPS.

EPS is more readily available than PUR and the manufacturing process is less specialised.

PUR has higher creep deflection than EPS so cannot span as far. Creep deflection is where a loaded member moves gradually over time; something all plastics are prone to. While initially providing higher strength values the gradual movement in PUR means engineers cannot specify as great a distance with PUR SIPs.

PUR SIPs are more expensive than EPS SIPs

PUR is a thermosetting plastic so doesn't melt. EPS does melt when it gets hot enough. The beauty of any SIP is that the skins protect the core for a period of time, and as there is no free air in the panel they tend to extinguish any flames by choking their air-supply. EPS used in Formance panels has a flame-retardant so won't propagate fire; it simply pulls back from the heat source and forms a hard skin. SIPs have a good fire record and can be used where fire rated walls are required. Refer to Method technical information for specifying Formance firewalls.

PUR is a thermosetting plastic so once it has been used in a panel that's it. Unlike an EPS core that can be recycled for other uses later should the need ever arise.

Product Development 
The vast majority of the ongoing product development in North America supported by the Structural Insulated Panel Association (SIPA) is on EPS SIPs. Ongoing product tests and studies involving EPS SIPs ensure the Formance panel continues to remain at the cutting edge of SIP technology worldwide. 

How long would a first-time builder take to install a SIP house compared to conventional framing?

We supply pre-cut panels according to shop drawings - it's like a big jigsaw puzzle - so SIPs are slightly faster. The actual panel erection vs frame erection speed will be about the same, but there is no straightening required (4-8 days depending on the size of the building), and the overall program saving is significant because the internal trades can get into the building and begin their work as soon as the SIPs are standing. They don't have to wait until the cladding is installed. A study made by RS Means in the USA in 2007 is useful and showed a labour saving of around 50% when comparing SIPs to site framing. Note this study is often inaccurately quoted in NZ to prove the speed advantage of SIPs. In NZ we rarely build stick houses by site framing, instead, we use prenailed frames and trusses. The real benefits of SIPs are not so much in the time savings as in the energy savings. 

The Formance process involves producing shop drawings from which we cut the panels. It means the windows can be ordered to match the openings shown on the shop drawings reducing the wait time for windows to arrive.

To get real speed on the job site we suggest considering preassembly. In commercial projects we have been preassembling panel sections in lengths up to 6m which slash the panel erection time to just a few hours. Panels are delivered to site by HIAB and lifted into place directly from the deck of the HIAB. Our first job supplied in this way resulted in 100 m of wall being installed in 8 hours.

Why is air tightness important?

The building science expert John Straube best answers this question: "Stopping air is the second-most-important job of a building enclosure. Next to rain, air leaks through walls, roofs, and floors can have the most damaging effect on the durability of a house. Uncontrolled airflow through the shell not only carries moisture into framing cavities, causing mould and rot, but it also can account for a huge portion of a home’s energy use and can cause indoor-air-quality problems."

What effect do Formance SIPs have on indoor air quality?

The beauty of a Formance SIP home is that it's very airtight; allowing you to have optimum control over the inside environment. The answer is to mechanically ventilate the building with a heat recovery ventilation system. These units are very simple, they simply take the energy from the warm stale air from inside the house and give it to the cooler air coming into the house - at about 80% efficiency. They run 24/7 and can use less power to run than a standard 100W lightbuld. Super healthy filtered air comes in, and the inside environment stays warm and dry for the ultimate healthy home. Talk to us about who to use for your project.

Controlled ventilation filters out contaminants and allergens, and also allows for incoming air to be dehumidified, reducing the possibility for mould growth. There are a variety of ventilation strategies that can be employed to provide fresh air to airtight homes. These vary by climate, but most are relatively inexpensive and operate on automatic control systems without the need for homeowner action.

Formance panels do not contain any VOCs or other harmful chemicals that can affect occupant health. The components used to make SIPs (foam, oriented strand board, and adhesive) meet some of the most stringent standards for indoor air quality.

EPS uses pentane, a non-CFC blowing agent that dissipates shortly after production. EPS has no offgassing
SIP homes made using identical components to Formance panels have qualified under the American Lung Association’s Health House® indoor air quality standard
The adhesives used in Formance panel production do not contain any measurable amounts of volatile organic compounds (VOCs) that can be harmful to occupants
Oriented strand board (OSB) does not contain urea formaldehyde adhesives and meets the world’s leading formaldehyde emissions standards, including the U.S. HUD, Manufactured Housing Standard, the California Air Resources Board (CARB) Air Toxic Control Measure for Composite Wood Products and the European EN-300 Standard
You can rest assured your new Formance home will be one of the healthiest spaces you've been in.

How do Formance SIPs fare in an earthquake?

Remarkably well. Formance SIPs have two key attributes that really stand out; they have huge strength and they have great ductility. So not only do they withstand the applied force of an earthquake really really well but they have a unique ability to take the shock out of the movement by allowing some non-permanent flex in the stucture. Engineers call this ductility. Small but enough to significantly reduce the impact of the multi-directional earthquake cycle. More rigid and brittle materials like concrete tend to fail abruptly without warning and once gone they require extensive remediation or replacement. The engineers measure resistance to earthquake movement in Bracing Units and have other more technical terms for it but for the rest of us it simply means they can withstand severe earthquakes and keep us safe inside. Check out our page on how Formance panels handle earthquakes for more information.


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