Wellington Builders | Design & Architecture Services | Eco-Friendly Design | High Performing Home | Structural Insulated Panels | Energy-Efficient Home
When it comes to building homes that can stand up to the toughest of nature's challenges, Structural Insulated Panel (SIP) homes are proving they have what it takes. New Zealand, known for its beautiful landscapes and unfortunately frequent earthquakes, offers a great example of how durable these homes can be. SIP homes are becoming a top choice for those who want a strong, reliable place to live.
If you’re considering building a SIP home, then read on to learn how these homes hold up against earthquakes and fires, with real-life examples and expert opinions to back it up.
Why Are SIP Homes So Tough?
SIP homes are built with panels that have an insulating foam core between two layers of oriented strand board (OSB) or ply. This unique construction gives them several major advantages:
● High Strength-to-Weight Ratio: SIPs are incredibly strong for their weight, providing a solid structure that can handle a lot of force.
● Air Tightness and Insulation: The continuous insulation and air barrier properties of SIPs help prevent moisture and reduce thermal bridging, adding to their durability.
● Seamless Construction: Our Polystyrene SIPs are glued together, creating a unified and rigid structure that enhances stability. Our Polyurethane SIPs are even stronger - in the bonding of the foam, the actual polyurethane is used as a bonding agent to the board itself.
Earthquake Resilience
SIP homes use an interlocking timber system that lets the house move with the ground during an earthquake instead of fighting against it. This flexibility, combined with the strength of the materials, helps the home absorb and distribute the energy from the quake, keeping it safe. It also means the house remains livable with fewer repairs needed after a quake, saving homeowners from big rebuilding costs and headaches.
Case Study: Christchurch (2011) and Kaikoura (2016) Earthquakes
In the big earthquakes that hit Christchurch in 2011 and Kaikoura in 2016, SIP homes showed off their strength. For example, there was a SIP home in Waiau, close to the epicentre of the 7.8 magnitude quake in Kaikoura. This house came out almost unscathed, while many other buildings around it were seriously damaged.
Expert Insight
BRANZ has been conducting ongoing tests on SIPs in NZ to see how well they perform in an earthquake and fire. The tests, co-funded by EQC, tested several SIP configurations under seismic loading to find out how they perform during an earthquake and BRANZ senior structural engineer Dr David Carradine is enthusiastic about the results to date. "So far we’ve found that the ductility of the system - that’s the ability to deform without actually failing - is very good," says David. "The way the panels have responded to simulated earthquake loading is exactly what we want to see from an engineering point of view for low-rise buildings."
This is what they found:
● SIP systems provided suitable ductility, strength and stiffness for prescriptive and specific engineered wall bracing designs.
● Damage observed during cyclic loading was less for SIPs than most of the more commonly used bracing systems like plasterboard and plywood.
● There were no significant performance differences among the different types of SIPs tested having timber-based panel skins.
Fire Resistance
SIP skins protect the core for some time, and because there is no free air in the panel, they tend to extinguish any flames by choking their air supply. Also, the foam used in our EPS panels contains a flame-retardant, meaning they won't propagate fire. Instead, they pull back from the heat source and form a hard skin. Both EPS and PUR panels can be used as fire rated systems.
SIPs are still relatively new to New Zealand so there is little information about their performance in our specific environment, so we’ll discuss a case study from overseas.
Case Study: Sonoma County Wildfires (2017)
During the wildfires in Sonoma County, California, several SIP homes showed their fire-resistant properties. One home, built with SIPs and additional fire-resistant materials, survived with only minor exterior damage while nearby structures were destroyed.
Expert Insight
US fire safety expert James Morgan emphasizes, "While no material is entirely fireproof, SIP homes can be designed to meet stringent fire-resistance standards." In New Zealand, we recommend using a cladding such as Nu-Wall which is manufactured from solid extruded aluminium. The powder coat finishes are less than 1mm thick and are therefore considered to be non-combustible by the New Zealand Building Code.
SIP homes are proving their strength when it comes to natural disasters. Their lightweight yet strong build, airtight construction, and smart design make them tough against earthquakes and fires, giving homeowners peace of mind.
If you’d like to know more about SIPs, check out the downloadable resources on our website or get in touch! We would love to help you see how building a SIP home is THE way to build in New Zealand.
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