Prefabrication: Structural Insulated Panels (SIPS) & Passivhaus – Murray Robertson, Robertson Architects NZ

SIPS, or structural insulated panels are a fast and efficient way to achieve very high thermal performance.

In today's episode, we continue exploring prefabricated panel solutions. We investigate the design of a passive house built from SIPS on a very challenging site in the oceanic temperate climate of Wellington, in New Zealand. Architect Murray Robertson, the director of Robertson Architects, shares the inside story of his Bell House project.

Today we'll explore the process, benefits and costs of SIPs and when they're an ideal solution.

Australian Architects can claim formal CPD hours for these podcasts.

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• PODCASTKey points summary, timestamps and resource links
• FREE RESOURCESTranscript edited into clear Q&A.
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KEY POINTS SUMMARY

1. Structural insulated panels or SIPs are used in floors, walls and roofs for residential and light commercial buildings. The panels are made by sandwiching a core of rigid foam plastic insulation between two structural facings and in this case Murray used oriented strandboard (OSB). SIPS are manufactured off site and are custom designed for each project.

2. SIPs panels do have some timber framing in them, but much less than a standard timber stud wall. The reduced timber content plus the polyurethane insulation deliver better thermal performance than standard insulated timber frame construction.

3. The external wall composition of this project was as follows:

• The basic external shell was a 165 mm thick SIPS panel.
• Externally, the ProClima weathertight membrane was fixed directly to the SIPS board and a 45x45 timber structural cavity batten attached to the outside of the membrane for the external cladding, and
• Internally, 45 x 45 timber battens were fixed to the SIPs, creating space for services, additional insulation and attachment for internal plasterboard lining.

4. Internally, the oriented strandboard lining can be exposed rather than covered with plasterboard to save costs, but this approach makes access to services much more challenging. Additionally, since the strandboard wall serves as the finished surface, it requires protection during construction.

5. SIPS are very airtight, making them very appealing for use in Passive House projects. Only the joints in the very large SIPS panels require taping.

And finally,

6. Important design considerations when using SIPs include:

• Lintels above doors and windows cannot be concealed within the ceiling, meaning that floor to ceiling glazing is not possible, and
• SIPS roof panels stop at the wall line resulting in no eaves overhang. Therefore, a custom solution to attach eaves is...