Has the Japanese approach to sustainable housebuilding got anything to offer house builders in the UK? Robin Dodyk, technical director of Oregon Timber Frame certainly thinks so, having just returned from industry visits in Osaka and Tokyo and the 10th World Conference on Timber Engineering held in Miyazaki, Japan. This is a global event that attracts engineers, architects, researchers and timber users from around the world – although Oregon was the only UK timber manufacturing company to attend.
Housebuilding in Japan is undertaken at the rate of 1.2 million homes per year, for a population of more than 100 million – roughly 10 times the UK build rate for almost twice the population. Construction methods break down as 40% post and beam timber frame; 40% lightweight steel frame; and 20% heavy steel frame or concrete.
Japanese housebuilders have to work within the constraints of cold winters and hot humid summers; seismic threats; typhoons and very high land costs – typically 1 million yen or £5,000/m2. This chronic shortage of building land results in very high housing densities where a 160m2 plot will typically support a house with a 150m2 footprint. The appreciating asset in Japan therefore is the land, not the houses, which at present are routinely demolished after 20-30 years. On top of all this, extreme site access difficulties mean that large-scale panel solutions – building roof on the deck and floor cassettes – are impossible.
Against this background, the Japanese government is promoting a tree-loving, waste-averse culture, where new build is expected to be zero or low carbon and where zero emission of construction waste is also targeted. Developers are now required to respond to these standards by taking into consideration technology, IT, eco-design and “home amenity” and with houses now being built to last for at least 40 years.
Housebuilders have responded with an approach which marries traditional Japanese design principles with modern technology. “They use design principles that have worked for centuries with state-of-the-art robots to factory-produce frames that virtually ‘click together’ on these tight sites,” said Dodyk. “Then they add hi-tech ‘gizmos’ like photovoltaics and hydrogen cells to offset energy use, such as air conditioning in the summer.”
Traditional principles mean, for example, that houses are designed to maximise airflow internally throughout the summer, with high level ventilating transoms, moveable screens and walls and ventilation grids in the floors. Deep eaves and overhanging balconies shade the upper and lower floors from the heat. Tiny, beautifully designed gardens planted with leafy foliage also maximise shade and airflow. Overall, it’s a passive approach to design which maximises effect while minimising materials use and running costs.
In terms of manufacture, the tight sites and waste-averse culture have also led to a cost-effective, sustainable approach to the manufacture of components – a process described by Dodyk as “serious value-engineering”.
“Whereas in the UK we would manufacture a load-bearing beam as one long piece of engineered timber, of the same dimensions throughout, the Japanese approach is different,” he said. “Tight sites and restricted access mean that the beam is likely to be manufactured in short sections, to be fixed together on site. The Japanese have identified that this gives an opportunity to engineer each section differently, responding to the different loadings required along the beam. So what was initially a practical response to building in cramped conditions is now also delivering savings in costs and cutting material waste as a matter of routine.”
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The site team |
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Metal tie of beam to beam at external wall |
Keywords: Oregon Timber Frame
