Structural Insulated Panels (SIPS)

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Structural Insulated Panels – more than you wanted to know – Part I

what is a SIP? A SIP is a prefabricated panel consisting of two layers of Oriented Strand Board (OSB) sandwiching a layer of expanded polystyrene or urethane foam.



more on the technical details later – in the mean time:

The history of building with SIPs

SIPs are still a relative novelty in the UK – the majority of our houses are still built with brick and block – but the burgeoning interest in self-building and the desire to create energy efficient houses mean that SIPs are gaining in popularity.

This may surprise to our friends in the US where building with SIPs goes back to the 1950s. In fact the earliest laminated prefabricated panels (made from layers of plywood and tar paper) were used by Frank Lloyd Wright in the Usonian houses built in the 1930:

when reading about FLW’s laudable attempt to create affordable but beautiful homes I came across the English equivalent, Walter Segal.

Mr Segal (a naturalized Brit having escaped Nazi Germany) was also a pioneering architect who – inspired by the long tradition of simple timber framed buildings in the US – proposed a low cost, simple to construct design that he thought could help with the housing crisis that followed WW2.

The genius of his idea was that the designs were modular, configurable and designed to be put together by self-builders. His great belief was that there was a large part of the population who, if the process was made simple enough, could build themselves effective housing simply and cheaply.

He realised that by using readily available materials like standard plywood and plasterboard sheets, reducing the weight of the building – allowing our favourite plinth foundations – and removing the needs for wet trades like plastering, most competent DIYers could take care of the whole building process. And the icing on the cake was that, since the families who would live in the houses would also need to be involved in the design and build, this approach would create communities as well as houses.

An enterprising council in Lewisham sponsored the construction of about 50 of the houses in the 1970s and early 1980s. Walter died in 1985 but his ideas have continued to influence architects and self builders alike , and I hope in some small way are reflected in my shed. I am sure if he had lived another 20 years he would have been building with SIPs too.

Some Walter Segal houses

Read more about the brilliant Mr Segal here:

Back to SIPs – Alden Dow (architect and brother of the founder of Dow Chemicals) was impressed by the Frank Lloyd Wright project, seeing how the panels could significantly reduce the construction time, but he saw an opportunity to improve the end result by adding insulation.

After much experimentation he developed a panel with an insulating core of styrofoam, thus inventing the first SIP. Although he built a number of houses using these panels it took several decades for a reasonably inexpensive production process for the panels to be worked out and, during that time, the cost of labour and the energy needed to head even a poorly insulated house was still relatively cheap compared to material costs.

These factors hindered adoption of the ‘new’ technology, however today things are changing rapidly, and in the developed world labour and energy costs now represent a much bigger overall proportion of the costs of building, so we find ourselves at the dawn of the age of the SIP.

In the next instalment – why SIPS are a good idea.

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