INSIGHTS

2023.03.07

R&D DISCUSSION Vol. 44

Building fire-resistant wooden buildings [Part 1]

Noboru Yasui, Architect and Chairman of NPO team Timberize

R&D DISCUSSION TOP

Q: In recent years, wooden structures and buildings made from wood have been gaining attention, and there have been an increasing number of cases of large-scale public buildings such as schools and government offices being built. Why is "wood" architecture becoming more popular now?

A: In Japan, many wooden buildings were destroyed by fire during World War II, and in 1950, five years after the end of the war, the Building Standards Act was enacted with the goal of making cities fireproof. In other words, modern Japan once rejected wooden construction and built cities mainly with steel-framed or reinforced concrete structures, but after the 1980s, regulations on wooden buildings were gradually relaxed, provided safety could be ensured, and rationalization has progressed [Slide 1].

First, in 1987, wooden buildings were allowed to exceed the 13m height or 9m eaves height limit, which had been set before. Furthermore, the concept of "burning margin design" was introduced to the fire prevention standards, which uses thicker wood to ensure fire safety. In 1992, the Building Standards Act previously classified buildings into "fireproof buildings" that would not collapse in the event of a fire, and "others." The concept of "semi-fireproof buildings" with structures that suppress the spread of fire was created, allowing wooden buildings up to three stories high to be semi-fireproof. Then, in 2000, the fire prevention regulations were revised to include performance standards, making it possible to design "fireproof buildings" made of wood. In effect, there were no restrictions on height, number of floors, or size, and the law was changed to something that was unique in the world. However, initially, most of the cases were residential, but with advances in wooden construction and wood utilization technology coupled with deregulation, and amendments in 2015 and 2019, it is now possible to design three-story wooden schools and four-story wooden offices with semi-fireproof structures, and non-residential cases are finally on the rise.

The Act on the Promotion of Wood Use in Public Buildings, etc., enacted in 2010, was also a major turning point. The following year, in 2011, we launched the NPO team Timberize, which aims to promote the use of wood in cities, and began drawing pictures of wood-based Omotesando in Tokyo and showing them to the public [Slide 2]. However, there were many negative opinions, such as "There's no way this can be done with the law." For a long time, it was possible under the law, but it was not known and no one wanted to do it, but finally last year, an 11-story pure wood high-rise building (Port Plus Obayashi Yokohama Training Center) was completed. In the picture of Omotesando, we only drew a modest seven stories, but 11 years later, something that exceeds that has been realized, and even we in the wood construction industry recognize that the world has changed at a frightening pace. With deregulation aimed at realizing a carbon-neutral society in 2050 and the amendment of the Wood Use Promotion Act for Public Buildings, etc. (2021), there is no reason to put a stop to the spread of wood. I believe that in the future, wooden construction will receive more and more attention, and people known as wooden construction experts will play a greater role.

[Slide 1] The trend towards rationalization and relaxation of the Building Standards Act.
[Slide 2] Image of wood-based materials in Omotesando, Tokyo (Produced by NPO team Timberize, 2010).

Q: Compared to steel-framed and reinforced concrete structures, wooden structures are perceived as being more vulnerable to fire, corrosion, and cracking. Please tell us how to design with wood in a good way.

A: Actually, wood is a flammable material that does not burn easily. When we conducted an experiment with the Ministry of Land, Infrastructure, Transport and Tourism on "interior restrictions" aimed at preventing the spread of fire, the results showed that a space with wood walls and plasterboard ceilings did not spread fire for 20 minutes [Photo 1]. When well-dried wood with a thickness of 15 mm and a moisture content of 15% is used for the walls, the amount of moisture contained per square meter is about 750 ml. In other words, it is like storing 1.5 500 ml plastic bottles of water for every square meter of wall, so it is difficult for a fire to catch. Putting wood on a wall is the same as having a sprinkler system, although the amount of water is limited.

Let's review the properties of wood [Slide 3]. First, specific gravity. A lighter structure reduces the force applied during an earthquake, so wooden construction is more advantageous in terms of earthquake resistance than steel-framed or reinforced concrete construction. Next, regarding thermal conductivity, wood has about 1/10 that of concrete and about 1/350 that of steel, so we can see that it is difficult for heat to be transmitted. In addition, wood has a high specific heat, and is slow to heat up and cool down, so buildings that consume less energy can be built. Furthermore, it has high heat insulation and fire spread suppression properties, so if a fire door is made with a thickness of 30 mm using the ability of wood to burn 1 mm per minute, it is possible to create a fire compartment with a performance of 30 minutes. A typical aluminum fire door has a performance of 20 minutes, and the surface temperature rises to 400 to 500°C, but wood has a low thermal conductivity so the inside temperature does not exceed 100°C. I think the only thing that is inferior to steel-framed or reinforced concrete construction is the sound insulation between the upper and lower floors.

Rot and discoloration are not defects of "wooden construction," but of the material "wood." However, mushrooms cannot grow unless wood rots. Camping is no fun if wood does not burn. These are both disadvantages and advantages of wood. Wood rots and discolors due to "water," so you just need to keep it from getting wet. Of course, you can treat it with chemicals, but the basic principle is not to wet materials that have already dried, and it is important to make sure that even if they do get wet, they dry quickly. If you can completely avoid contact with water, you can eliminate the disadvantages.

After graduating from university, I worked for a housing manufacturer that specialized in steel-frame construction, and then 20 years ago I started my own office specializing in wooden construction. Since I knew nothing about wood, I first went to sawmills and markets to thoroughly "study wood" and "learn from wood." Even now, when I go on business trips, I try to visit as many local sawmills as possible. The "yield" refers to the amount of unusable parts that crack or warp during the process of sawing logs and drying them. We store and preserve our own wood so that we can learn various characteristics from raw materials [Photo 2]. We buy our own logs to design and maintain our office desks [Photo 3]. I think that if you become interested in wood, it will be useful in your designs.

[Photo 1] An experiment on interior restrictions conducted jointly by the Ministry of Land, Infrastructure, Transport and Tourism, Waseda University, and others (2013).
[Slide 3] List of main performance characteristics of building materials.
[Photo 2] Understanding the sawing process.
[Photo 3] An office desk designed using purchased logs. It is oiled and maintained once a year.

[Slides 1 and 3, Photos 1-3: provided by Sakura Design Group Architectural Office, Slide 2: provided by NPO team Timberize]

Continued in Part 2

PROFILE

Architect, Chairman of NPO team Timberize

Noboru Yasui

Easy to climb

Born in Kyoto City, Kyoto Prefecture in 1968. After completing a Master's course in Architecture at the Tokyo University of Science Graduate School of Science and Engineering in 1993, he worked at Sekisui House Co., Ltd. before opening Sakura Design Group First Class Architect Office in 1999. He completed a doctorate in Construction Engineering at the Waseda University Graduate School of Science and Engineering in 2004. He is currently a part-time lecturer at the Gifu Prefectural Academy of Forest Culture, a director of the NPO Wood Architecture Forum, a specially appointed professor at Kochi Prefectural Forestry College, a researcher at the Waseda University Institute of Science and Engineering, chairman of the NPO team Timberize, and a research fellow at the University of Tokyo Institute of Industrial Science.

OTHER DISCUSSIONS

R&D DISCUSSION Vol.56

Mind change――
Aiming for a company that will develop into the future [Part 2]

Hidehito Kawahara, President and CEO of ALFA PMC

R&D DISCUSSION Vol.55

Mind change――
Aiming for a company that will develop into the future [Part 2]

Hidehito Kawahara, President and CEO of ALFA PMC

R&D DISCUSSION Vol.54

Mind change――
Aiming to become a company that will develop into the future [Part 1]

Hidehito Kawahara, President and CEO of ALFA PMC

R&D DISCUSSION Vol.53

Next-generation transportation and future urban planning [Part 2]

Professor Akinori Morimoto, Faculty of Science and Engineering, Waseda University; President, City Planning Institute of Japan

R&D DISCUSSION Vol.52

Next-generation transportation and future urban planning [Part 2]

Professor Akinori Morimoto, Faculty of Science and Engineering, Waseda University; President, City Planning Institute of Japan

R&D DISCUSSION Vol.51

Next-generation transportation and future urban planning [Part 1]

Professor Akinori Morimoto, Faculty of Science and Engineering, Waseda University; President, City Planning Institute of Japan

R&D DISCUSSION Vol.50

The world is full of possibilities
--Perceive playfully and take action! [Part 2]

Nobuyuki Ueda Professor Emeritus of Doshisha Women's College of Liberal Arts, Director of Neo Museum

R&D DISCUSSION Vol.49

The world is full of possibilities
--Perceive playfully and take action! [Part 2]

Nobuyuki Ueda Professor Emeritus of Doshisha Women's College of Liberal Arts, Director of Neo Museum

R&D DISCUSSION Vol.48

The world is full of possibilities
--Perceive playfully and take action! [Part 1]

Nobuyuki Ueda Professor Emeritus of Doshisha Women's College of Liberal Arts, Director of Neo Museum

R&D DISCUSSION Vol.47

Light is Life: Humans on the Solar Earth [Part 2]

Hiroyasu Shouji ShojiLighting Designer

R&D DISCUSSION Vol.46

Light is Life: Humans on the Solar Earth [Part 1]

Hiroyasu Shouji ShojiLighting Designer

R&D DISCUSSION Vol45

Building fire-resistant wooden buildings [Part 2]

Noboru Yasui, Architect and Chairman of NPO team Timberize

R&D DISCUSSION Vol.44

Building fire-resistant wooden buildings [Part 1]

Noboru Yasui, Architect and Chairman of NPO team Timberize

R&D DISCUSSION Vol.43

What is a sign? What is sign design?
What? [Part 2]

Toshiaki Yashima Information Designer

R&D DISCUSSION Vol.42

What is a sign? What is sign design?
What? [Part 2]

Toshiaki Yashima Information Designer

R&D DISCUSSION Vol.41

What is a sign? What is sign design?
What? [Part 1]

Toshiaki Yashima Information Designer

R&D DISCUSSION Vol.40

Data-driven urban development that makes people happy [Part 2]

Taro Hitokoto Director of Neural Pocket Co., Ltd.

R&D DISCUSSION Vol.39

Data-driven urban development that makes people happy [Part 1]

Taro Hitokoto Director of Neural Pocket Co., Ltd.

R&D DISCUSSION Vol.38

Japan's Strategy for Achieving Carbon Neutrality by 2050 [Part 2]

Takuzo Saito Director of the Evaluation and Assessment Department, Housing and Construction Center, Better Living Foundation

R&D DISCUSSION Vol.37

Japan's strategy for achieving carbon neutrality by 2050 [Part 1]

Takuzo Saito Director of the Evaluation and Assessment Department, Housing and Construction Center, Better Living Foundation

R&D DISCUSSION Vol.36

The "extra" required for architecture revealed through regional projects [Part 2]

Yasushi Takeuchi Professor, Tohoku Institute of Technology (-2021), President and CEO, Abisei Planning Co., Ltd. (2022-)

R&D DISCUSSION Vol.35

The "extra" required for architecture revealed through regional projects [Part 1]

Yasushi Takeuchi, Professor, Tohoku Institute of Technology (-2021), President and CEO, Abisei Planning Co., Ltd.

R&D DISCUSSION Vol.34

Before-Before Architecture Theory
Design techniques that unravel history [Part 2]

Toru Ajisaka, Professor, Kagoshima University

R&D DISCUSSION Vol.33

Before-Before Architecture Theory
Design techniques that unravel history [Part 1]

Toru Ajisaka, Professor, Kagoshima University

R&D DISCUSSION Vol.32

How to create a "water mass" that attracts adults
Turning aquariums into "media" through a customer-centric approach

Gen Nakamura Aquarium Producer

R&D DISCUSSION Vol.31

How to create a "water mass" that attracts adults
Sunshine Aquarium "Oasis in the Sky" [Part 2]

Gen Nakamura Aquarium Producer

R&D DISCUSSION Vol.30

How to create a "water mass" that attracts adults
Sunshine Aquarium "Oasis in the Sky" [Part 1]

Gen Nakamura Aquarium Producer

R&D DISCUSSION Vol.29

Wellness and Performance Management
How to Live in a New Era Vol.2 [Part 2]

Takayuki Hirai
Deputy Director of the CHO Office at DeNA Co., Ltd.; Representative of Ibuki LLC

R&D DISCUSSION Vol.28

Wellness and Performance Management
How to Live in a New Era vol.2 [Part 1]

Takayuki Hirai
Deputy Director of the CHO Office at DeNA Co., Ltd.; Representative of Ibuki LLC

R&D DISCUSSION Vol.27

A work style that brings about innovation
How to Live in a New Era Vol.1 [Part 2]

Takahiro Sakamoto
Representative of SSIN LLC, Advisor of KOKUYO Co., Ltd.'s Work Style Reform Project

R&D DISCUSSION Vol.26

A work style that brings about innovation
How to Live in a New Era Vol.1 [Part 1]

Takahiro Sakamoto
Representative of SSIN LLC, Advisor of KOKUYO Co., Ltd.'s Work Style Reform Project

R&D DISCUSSION Vol.25

Looking at the future design process through "Renovation" [Part 2]

Masataka Baba Architect

R&D DISCUSSION Vol.24

Looking at the future design process through "Renovation" [Part 2]

Masataka Baba Architect

R&D DISCUSSION Vol.23

Looking at the future design process through "Renovation" [Part 1]

Masataka Baba Architect

R&D DISCUSSION Vol.22

Architecture in Film: Special Effects TV and Comedy Films of the 1960s [Part 2]

Tatsuo Iso IsoArchitectural Journalist

R&D DISCUSSION Vol.21

Architecture in Film: Special Effects TV and Comedy Films of the 1960s [Part 1]

Tatsuo Iso IsoArchitectural Journalist

R&D DISCUSSION Vol.20

Pioneering the future with the power of design
Discovering Young Artists [Part 2]

Toshiki Kiriyama Director

R&D DISCUSSION Vol.19

Pioneering the future with the power of design
Discovering Young Artists [Part 2]

Toshiki Kiriyama Director

R&D DISCUSSION Vol.18

Pioneering the future with the power of design
Discovering Young Artists [Part 1]

Toshiki Kiriyama Director

R&D DISCUSSION Vol.17

The present and future of theater space
Research on Plaza Spaces Vol.3 [Part 2]

Masaji Ito + Kenji Maruyama Theater Workshop Co., Ltd.

R&D DISCUSSION Vol.16

The present and future of theater space
Research on Plaza Spaces Vol.3 [Part 1]

Masaji Ito + Kenji Maruyama Theater Workshop Co., Ltd.

R&D DISCUSSION Vol.15

How to create public spaces with 100% occupancy rate
Research on Plaza Spaces Vol.2 [Part 2]

Yuko Yamashita Yamashita, Network creator, Hiroba-nist

R&D DISCUSSION Vol.14

How to create public spaces with 100% occupancy rate
Research on Plaza Spaces Vol.2 [Part 1]

Yuko Yamashita Yamashita, Network creator, Hiroba-nist

R&D DISCUSSION Vol.13

Designing "social fluctuations"
Research on Plaza Spaces Vol.1 [Part 2]

Shoji Okabe
Evangelist at Snow Peak Business Solutions Co., Ltd., and co-representative of the nonprofit organization "Hama no Toudai"

R&D DISCUSSION Vol.12

Designing "social fluctuations"
Research on Plaza Spaces Vol.1 [Part 1]

Shoji Okabe
Evangelist at Snow Peak Business Solutions Co., Ltd., and co-representative of the nonprofit organization "Hama no Toudai"

R&D DISCUSSION Vol.11

A workplace that fosters innovation
Changing the environment changes the way you work [Part 2]

Tetsuo Kobori Architect

R&D DISCUSSION Vol.10

A workplace that fosters innovation
If the environment changes, the way you work will change [Part 2]

Tetsuo Kobori Architect

R&D DISCUSSION Vol.09

A workplace that fosters innovation
Changing the environment changes the way you work [Part 1]

Tetsuo Kobori Architect

R&D DISCUSSION Vol.08

Environmentally friendly architecture and healthy spaces drive the economy
ESG Investment and Wellness Offices [Part 2]

Shinichi Tanabe Professor, Department of Architecture, School of Creative Science and Engineering, Waseda University

R&D DISCUSSION Vol.07

Environmentally friendly architecture and healthy spaces drive the economy
ESG Investment and Wellness Offices [Part 1]

Shinichi Tanabe Professor, Department of Architecture, School of Creative Science and Engineering, Waseda University

R&D DISCUSSION Vol.06

The centripetal force of a single sketch that depicts a scene from the future [Part 2]

Tetsuo Fukuda Industrial Designer

R&D DISCUSSION Vol.05

The centripetal force of a single sketch that depicts a scene from the future [Part 1]

Tetsuo Fukuda Industrial Designer

R&D DISCUSSION Vol.04

Thinking about future redevelopment from postwar "buildings" [Part 2]

Shunsuke Kurakata historian

R&D DISCUSSION Vol.03

Thinking about future redevelopment from postwar "buildings" [Part 1]

Shunsuke Kurakata historian

R&D DISCUSSION Vol.02

Architecture: Perspectives from Industrial Design [Part 2]

Kozo Yamada, Director and Advisor, GK Design Corporation

R&D DISCUSSION Vol.01

Architecture: Perspectives from Industrial Design [Part 1]

Kozo Yamada, Director and Advisor, GK Design Corporation
R&D

Update : 2018.09.21

Tags

PAGE TOP