New Building Systems

ABOVE: This house is an oak framed home that was built using SIPs. The house features in our self build projects section. Read more about this project.

People like answers. If you are spending loads of dosh, you want to ensure that you are spending it wisely. So frequently, in my role as a building pundit, I get asked very direct questions, such as: “What is the best way to build a house?” and “Can I really build a house without central heating?” But I am reluctant to give answers to these questions.

A recent email typifies the awkward position I find myself in:

“I am keen to build as energy efficient a house as is reasonably practical. I am persuaded that SIPs (structural insulated panels) would be a good build system, but am worried about the apparent conflict between the need for thermal mass to act as a heat buffer and the relatively lightweight construction usually used for timber frame and SIPs houses. I am also interested in your views about ventilation systems. My instinct is to go for breathability, airtightness, openable windows and perhaps some passive ventilation but not having to rely on a mechanical system. What do you think?”

You can summarise my thoughts in just two words: ‘Good luck’. While it’s one thing to have a good understanding of what these issues are, it’s quite another to be able to provide answers. The fact that there is now a wider choice of building systems and materials on offer just makes matters more complex.

Take SIPs. Structural insulated panels have been around for over 50 years internationally, and experi - mental examples were built in the UK in the 1970s. But it wasn’t really until Kingspan got involved in 2000 that SIPs became viable for self-builders. Early on, several self-builders took the plunge and ended up being guinea pigs for contractors who knew nothing about building with SIPs. However, I felt SIPs were basically a good idea and that the product was being let down by the builder’s ignorance or complacency.

But the market has matured and there are now builders who know exactly how to build a SIPs house. Consequently there are more and more self-builders who are delighted that they have created homes which need very little space heating and sometimes none at all.

Up until 2006, I had visited half a dozen SIPs sites and they had all experienced problems; invariably as a result of poor design work or construction methods. Since then, I have visited several more and each one has been successful. So, should you avoid any new building technique that hasn’t got a five-year track record? And if SIPs have turned the corner, are they now better than timber frame? How does either method compare with masonry build? All good questions to which I don’t have a simple yes-or-no answer.

It’s more complex still because, as my emailer points out, the choice of building system often has ramifications on the choice of services. SIPs sell themselves on airtightness and most people specify a whole-house mechanical ventilation system with a SIPs house — the indoor air quality is controlled and the heat gets evenly distributed. So far so good. But you don’t get ‘breathability’ with SIPs. Nor much in the way of thermal mass. And what happens to the fantastic airtightness levels if the family likes to sleep with the windows open? More good questions to which I don’t have ready answers.

For the record, I am not convinced that ‘breathability’ actually means very much. I have doubts as to the importance of thermal mass. On ventilation systems, I hold my hands up and say I still don’t know enough to be able to say X is better than Y. And I sympathise hugely with anyone struggling to make sense of these issues. There’s never been more choice — and it’s never been more confusing!

Further reading:

• A Guide to Construction Systems
• SIPs: Faster, Greener, Warmer?
• Natural Building Alternatives