Recommendation of Wooden Architecture

The movement towards achieving a decarbonized society by 2050 is gaining  momentum. Some European countries have
introduced regulations on CO₂ emissions in construction, and there is a move to make embodied carbon calculation and reporting mandatory for all buildings in EU member states by 2030. The reduction of embodied carbon, which includes any CO₂ created during construction process of new construction, remodeling, and demolition, is a mandatory requirement of the project.
Particular focus is placed on reducing the upfront carbon created during manufacturing and transportation of materials for new construction. In our think++magazine04(issued in December 2021), we centered on Our “Commitment to Carbon Neutrality. ”
The promotion of wooden architecture and wood utilization, one of the four priority issues we highlighted there,
are drawing attention from the perspective of CO₂ emission reduction, carbon fixation effects,
and recycling at the time of demolition. Now, let’s introduce our efforts towards wooden architecture and wood utilization.

The Future Value of Wooden Architecture and Wood Utilization
In addition to reducing CO₂ emissions, contributing to forest recycling, and improving the health and wellbeing of users, Buildings and spaces utilizing wood enhance asset value from an ESG investment perspective as environmentally and socially conscious architecture. Green Building Certifications assess criteria such as wood quantity and the use of locally sourced materials, emphasizing the responsible selection of materials that contribute to usage and forest circulation. Increasing wood utilization within our initiatives has significant impact. It contributes to biodiversity conservation through forest management, improve resilience against natural disasters like landslides, and revitalize local communities through a well-developed supply chain, including forestry. We believe it can contribute to realizing a sustainable society.

Our Commitment to Wooden Architecture and Wood Utilization
So far, we have focused on promoting wooden architecture in mid to large-scale buildings. They are low-rise buildings, but they are buildings that reaffirm the value of local timber, and buildings that are conscious of their relationship with the forest by considering the scope of timber procurement, such as using timber not only from local sources but also from sister cities and the same river basin. Furthermore, we have been developing stackable high-strength walls and joint systems to achieve mid to high-rise wooden buildings.
We believe it is important to further increase the amount of wood used, and thus, we will promote the use of wood in fire-resistant buildings in urban areas where it has been challenging. We will focus on the development of technologies for engineered wood products such as CLT*¹, LVL*², and composite materials, as well as technologies for using wood sourced directly from local forests. Additionally, we will propose diverse applications of wood, including advocating for biomass energy utilization in urban development, to promote both a low-carbon society and the sustainable circulation of forests.
* 1 Cross-Laminated Timber　* 2 Laminated Veneer Lumber

Three Stages of Wood Architecture and Wood Utilization Towards Carbon Neutrality
1   Aiming for CO₂ Reduction Through Wood Utilization

Utilizing Wood for Interiors and Exteriors
We use wood in interior design, such as for ceilings, walls, and furniture, and in exterior design, such as for eaves. This approach applies not only to new constructions but also to renovations and tenant spaces in skyscrapers.

The approximate amount of wood usage per unit area  0.0020㎥/㎡ Chuo Ward Office, ChuoWardCultural Center, Kobe City Total Floor Area : 19,341㎡ The main structure is made of steel frame. Toensure durability and create a wooden texture on the exterior, a 30mm thick wooden material is used for the eaves ceiling of the stacked deck.		The approximate amount of wood usage per unit area  0.0039㎥/㎡ New Headquarters of Nihon Sekkei think++nexus Total Floor Area : 6,796㎡ Wood materials are mainly used at the entrance area. The active use of wood, including wooden furniture with thick planks, creates a warm atmosphere in the high-rise tenant offices.

2  Partial Wood Construction for Further CO₂ Reduction

Using Wood as Structural Components
In addition to interior and exterior wood utilization, we incorporate wood construction for columns, beams, floors, and walls. By using thick wooden panels for surfaces, particularly in floors and walls, we significantly increase wood utilization compared to interior applications.

The approximate amount of wood usage per unit area  0.034㎥/㎡ Takahama Town Hall /Public Hall Total Floor Area : 7,414㎡ In the public hall building, which combines RC and wooden construction, locally sourced materials were used for the traditional timber framing of the entrance hall and other areas.		The approximate amount of wood usage per unit area  0.070㎥/㎡ Cosmos Fukiage Hall Total Floor Area : 4,316㎡ The RC structure at the facility’s center supports seismic forces, enabling a lightweight wooden framework with solid steel columns and local timber laminated beams.

3  Pursuing Enhanced CO₂ Reduction Through Full-scale Wood Construction

Utilizing Wood in Pure Wood Construction or Hybrid Structures
Wood construction in this case means that the entire structure is made of wood or a mixed structure for fire resistance or structural reasons, and most of the structure is made of wood. High fire resistance and joint resistance are required for mid to high-rise buildings.

The approximate amount of wood usage per unit area  0.14㎥/㎡ International Christian University New Gymnasium Total Floor Area : 3,916㎡ A mixed structure of RC and wood, we are exploring innovative wood utilization by incorporating CLT for the formwork of RC columns and using LVL folding plate structures for the large roof.		The approximate amount of wood usage per unit area  0.24㎥/㎡ Nagareyama City Oguro-no-Mori Junior High School Total Floor Area : 14,568㎡ Wood structure, partly RC and S. Utilizing the largest amount of domestic wood, totaling 3,500㎥. Implementing supply chain management to procure a large quantity of timber at fair prices.

*The total floor area here indicates the floor area for wood use calculation

Development of Technology for Promoting Wooden Architecture and Wood Utilization
Checkered Wooden Seismic Wall（Nagareyama City Oguro-no-Mori Junior High School）

We developed earthquake-resistant walls with a wall ratio* of 15 times on one side and 30 times on both sides, allowing for a wooden structure with an open exterior. By arranging the walls in a checkered pattern on the corridor side and integrating them throughout all three floors, we achieved a fully wooden three-story school building. This checkered seismic wall design can be installed on the exterior or at the core of medium-rise wooden buildings of about five stories. *A value representing the strength of walls to resist horizontal forces on buildings, including earthquakes and wind.

Technological Development Wooden Seismic Elements

We are developing wooden seismic elements that can be used in steel-framed structures. These seismic walls provide both rigidity and ductility to withstand short-term seismic forces. By using laminated wood products available in the market, we can create seismic walls that are different from large-sized CLT panels, allowing for the incorporation of openings within a single wall.