Contributing to global environment preservation by expanding the scope of forest resource utilization and creating a "Forest Grand Cycle"

TAKENAKA CORPORATION

Outline

One of Takanaka’s missions is to “create the future of forests and cities through wood innovation.” To achieve this goal, Takenaka is working to achieve medium-rise and high-rise wooden structures, which up to now have been difficult to construct in urban areas. This will bring the warmth of wood to inorganic cities and create new domains for timber use. It will also achieve carbon sequestration in buildings and promote the recycling of forest resources that are a source of CO₂ sequestration. The intent is not simply to expand the use of wooden construction materials but rather to work with mountain communities and other stakeholders to achieve sustainable forestry operations and stimulate local industry and so on, in order to stimulate the economy and achieve major circulation of wealth and resources between urban and rural areas.

[Future efforts]

Promote the development of wooden construction technologies
Promote and expand the number of wooden construction projects
Pursue new commercial distribution channels for timber procurement
Work with stakeholders regarding timber use to deepen mutual understanding

Description

■ Background

The forests that cover 70% of Japan’s land area were cited as a CO₂ sequestration source for emissions reductions targets in the Paris Agreement, and their multifaceted functions that include soil conservation were emphasized. Conversely, progressive urbanization and the hollowing-out of regional areas have resulted in a decline in the forestry activities and regional economies that have supported forests, bringing to the fore the potential disaster risks of devastated forests.

Promoting wooden architecture in the construction industry that accounts for approximately 40% of domestic timber demand will make a major contribution toward the recycling and multifaceted use of forest resources as well as the stimulation of regional economies.

■ Activities of Takenaka Corporation

Severe restrictions are imposed on wooden buildings due to concerns regarding earthquakes and fires. Takenaka, however, saw achieving medium-rise and high-rise wooden structures in urban areas as a business opportunity and began developing fire-resistant timber technology that could be applied to medium- and high-rise buildings. Since 2013, we have successfully built 10 fire-resistant wooden structures in urban areas.

In addition, Takanaka has used this technology for activities aimed at achieving a Forest Grand Cycle®. This means going beyond the forest cycle of “planting and growing trees, cutting them down and then replanting” to “provide enrichment and other added value to cities through the use of wood, thereby stimulating the local economy in forest producing regions and encouraging timber use.”

The Forest Grand Cycle® is explained in detail below in (1) and (2).

(1) Expansion of urban wooden construction through the development of wooden construction technologies

Wooden buildings are easily damaged by fire. In the postwar period, the Japanese government imposed strict laws and regulations that made it difficult to construct large wooden buildings in urban areas.

For years, Takenaka has worked to develop technologies to open up new domains for the use of wood, namely the “medium-rise and high-rise wooden construction” that has heretofore been difficult. As the fruits of this effort, 18 urban wooden structures (both new and renovated) have been built, using technologies that include

- Moen-Wood®, a fire-resistant laminated timber;

- cross-laminated timber (CLT) use technologies; and

- “T-FoRest® series seismic retrofitting technology uses CLT and laminated veneer timber (LVL).

These efforts have helped to promote the use of domestically produced timber, which has not been sufficiently used in construction, and have opened up “urban wooden construction” as a new market.

Moen-Wood® fire-resistant laminated timber is a 3-layer column and beam member fashioned from mortar and domestically produced timber. Development began in 1998 and was completed after various trials. As of February 2020, Moen-Wood has been used in nine completed projects. Ongoing development has resulted in a line of various products;

- a two-hour fire-resistant product that can be used to build a 14-story wooden structure from the top down;

- square and round column products;

- a product for outdoor use; and

- a steel-reinforced laminate product that can be used for large-span bridges.

Moen-Wood can be used to create various wooden spaces and is expected to lead to increased opportunities for wood use in the future.

In addition, we made available our most versatile product, the 1-hour fire-resistant specification technology, for use by manufacturers in order to expand urban wooden construction by enabling the use of 1-hour fire-resistant Moen-Wood even in projects in which Takenaka is not involved.

(2) Integrated contribution to the environment, society and economy through “Forest Grand Cycle”® activities

Takenaka is helping to promote timber use through the following activities designed to achieve a “Forest Grand Cycle”®.

Use of wooden materials imparts a sense of well-being to a building interior and enriches the urban landscape.
The building of new commercial distribution channels that return appropriate profits to forestry producers and the fostering of a new market for urban wooden structures to replace the single family homes that are expected to decrease in the future will help to ensure sustainable forestry operations.
Educational activities to promote wooden architecture and timber use

Takenaka conducts various activities to help people learn about and become familiar with wood: public tours of wooden structures during and after construction, various types of exhibitions and seminars and the like to promote Takenaka’s wood technologies, and exhibits of the technologies at the Takenaka Carpentry Tools Museum (in the city of Kobe).

■Specific case study

Park Wood Takamori (new construction project)

[Building overview]

Completed: February 2019

Location: Sendai City, Miyagi Prefecture

Use: Apartment building

Scale: 10 aboveground stories, total floor area 3,605 m²

CLT is used for the floor and walls and Moen-Wood® is used for the columns.

[Participation in appropriate forest management by replanting on logged sites]

Replanting was conducted on the 1,300 m² site where the wood for the building was logged, with the participation of 15 Takenaka and related personnel. This was done to maintain the forest cycle over the next 50 years.

[Development of new commercial distribution channels]

In large-scale construction projects, it is rare for the prime contractor to directly purchase timber. However, by purchasing logs directly from forestry producers, we were able to return profits to the forestry producers. The development of simple distribution channels ensured timber quality and traceability, and it also encouraged production activities by enabling forestry producers to know where their wood was being used.

In addition, we cooperated with the CLT processing company to draw up a timber conversion plan and so on for the next process, helping to make timber use more efficient.

The improved economic viability and improved motivation on the part of related entities helped to ensure continued and expanded timber use in the future.

[Contribution to global environmental preservation]

Quantity of timber used in building: Approximately 200 m² → Approximately 207 tons of CO₂ sequestered
Planting of 440 nursery trees on the 1,300 m² logged site to renew the forest and stimulate forestry activities
Use of dry type lightweight timber to shorten the construction period by approximately three months as compared to reinforced concrete construction

■ Future activities

Takenaka will expand the number of projects and conduct the following activities as part of individual projects.

Target number of projects

2020: 11 or more 2021: 13 or more 2022: 15 or more

Pursue the development of wood construction technologies to enable the creation of diverse wooden spaces and building types, and work to reduce construction costs.
Pursue new commercial distribution channels for timber procurement.

Ensure timber traceability and quality up through processing, and achieve stabile timber procurement. Also return appropriate profits to mountain communities to enable reforestation after cutting to help preserve mountain forests.

Work with stakeholders regarding timber use to deepen mutual understanding.

Work with stakeholders with the aim of further expanding these activities.

Partner(s)

The partnership organization will differ depending on the project.

In the specific example of Park Wood Takamori, the owner is Mitsubishi Estate Co., Ltd. The timber supplier is Tajima Sangyo. The timber processing companies include Yamasa Mokuzai Co., Ltd.