The use of timber is being recognized as one means of achieving a carbon-free society and to help prevent global warming. Here we look at traditional Japanese techniques used in sustainable timber architecture that has been around since ancient times, as well as current initiatives and those for the future.
Kiyomizu-dera — a Temple That Is Still Standing after Hundreds of Years
One of Japan's traditional timber buildings, Kiyomizu-dera Temple in Kyoto was founded around 1,200 years ago. The current main hall building dates from 1633, having been rebuilt time and time again each time there was a fire.
In addition to regular repairs, Kiyomizu-dera Temple undergoes major renovations to its main hall stage once every 20 years or so, and to its roof every 40 to 50 years. Recently, the main hall roof was re-thatched for the first time in 50 years in Japanese cypress bark using a thatching technique known as hiwadabuki — used by traditional Japanese architects and registered as an Intangible Cultural Heritage by UNESCO.
The pillars that support the stage of Kiyomizu-dera Temple's main hall are made from Japanese zelkova trees that are about 400 years old. The durability of zelkova timber is roughly twice the age of the trees from which it is made. Construction materials for the major renovation works that will be needed over the next 400 years are being prepared by planting and cultivating trees at forests owned by Kiyomizu-dera Temple in Kyoto.
Extensive Use of Timber in Tokyo Olympic Games Venues
Around 40% of Japan's forested area consists of artificially-cultivated forests planted in the 1950s. These trees are now fully mature and ready to be used. If they are simply left to stand, the trees will decay and may lead to disasters such as landslides.
We can regenerate forests by cutting down mature trees and using them for large buildings, etc., and then planting new trees. In their growth stages, young forests absorb a large amount of CO2, which helps prevent global warming.
A lot of timber was used to build the venues for the Tokyo Olympic and Paralympic Games in Summer 2021. This is one of many concrete actions that we can take now to help the global environment.
The Challenge of Constructing All-Timber High-Rise Fire-Resistant Buildings
One construction company is building an all-timber high-rise building as part of efforts to achieve a carbon-free society. By using timber for the entire structure, including the columns, beams and floors, they are attempting to keep CO2 down and reduce emissions to lessen their environmental impact.
However, there are many challenges to overcome when building an all-timber high-rise building in a country like Japan where there are so many earthquakes. The building, with seismic isolation systems, uses newly-developed timber units that can withstand earthquakes thanks to their strength and tenacity, with the units placed at the joints between columns and girders where the force of the earthquake is at its greatest. The construction company is constructing timber buildings that we will be able to use with peace of mind for a long time.
Eco-Friendly and People-Friendly Timber Architecture of the Future
A long-established company that has been involved in the forestry sector for more than 300 years has started work on a research and development concept for the construction of a 70-story (350-m high) timber skyscraper to use the properties of timber to their fullest and provide an environmentally friendly structure that people will enjoy.
The construction of skyscrapers requires the use of huge amounts of timber, so further steps are being taken in terms of reforestation in order to meet the growing demand for timber buildings in the future. Researchers are trying to improve the efficiency of forestry cultivation by collecting and analyzing the genetic information from trees and selecting the best seedlings.
A new era of timber architecture has begun in Japan — one that builds on the sustainable philosophy embodied in traditional timber construction.