Yakisugi Deep Dive: Timber Origin, Production Process and Environmental Data

Martin Gottschlich

Yakisugi and the Environment: Forest Origin, Production and CO₂ Figures at a Glance

Yakisugi is a traditional Japanese cladding material and one of the few sustainable building materials produced without chemical wood preservatives – using fire alone.

Read on to learn about the properties of Yakisugi, why it makes timber more durable, and what a “proper” Yakisugi treatment involves.

In this article we cover the key aspects of Yakisugi production.

Key aspects to consider:

Timber as a renewable building material and carbon sink
Sustainably sourced timber
Production process
Carbon footprint
Durability – considering the product lifecycle
Certifications and standards

Timber as a Renewable Building Material and Carbon Sink

Among the most important building materials used in Europe – concrete, brick, steel, glass, asphalt, plaster, natural stone and timber – only timber stands out as a renewable natural resource. In addition, the production of timber is significantly less energy-intensive than that of most other materials such as steel, brick or concrete.

Forests play an important role in combating climate change, as they absorb and store significant quantities of carbon from the atmosphere. Our SGEC/PEFC-certified forests serve as a carbon sink.

One cubic metre of timber weighs on average 500 kg, half of which consists of carbon. This means that 250 kg of carbon is contained in one cubic metre of timber. When carbon is converted to CO₂ (oxidation), one kilogram of carbon produces approximately 3.67 kg of CO₂. 250 kg of carbon therefore yields 917 kg of CO₂, which equates to approximately one tonne of CO₂ per cubic metre of timber.

Sustainably Sourced Timber

Our Yakisugi is produced predominantly from timber harvested in the Nakamoto family’s own forests in Hiroshima Prefecture. The forests are certified to SGEC/PEFC standards (JIA-022 / CEFC 1901); Nakamoto Forestry Europe holds PEFC Chain of Custody certification (TÜV Nord 44 702 200728).

Many of the forests planted when the company was founded are now over 60 years old. The company uses primarily thinning timber, which is immediately replanted. We avoid clear-cutting and aim for a forest management cycle of 100 years.

Sustainable forestry practices can also have a positive effect on biodiversity, as well-managed forests can provide habitat for a variety of plant and animal species. The philosophy of sustainable forestry is deeply embedded in the DNA of Nakamoto Forestry.

Nakamoto Forestry operates its own tree nursery for raising new seedlings and saplings, as well as its own forester’s workshop, which maintains our forests on an ongoing basis. This includes activities such as pruning, thinning, and removing broken branches or snow to protect and care for the trees.

Our forestry work also reflects our responsibility for preserving the environment in the region. Many of our forests are located in the headwaters of the Ota River. When working near mountain streams, measures are taken to prevent sediment from entering and damaging water resources downstream. Attention is also paid to the forest floor vegetation to reduce soil erosion. In planted forests, areas where understorey vegetation is not growing are promptly thinned to allow the vegetation to recover.

The Senryo Mountain, also managed by Nakamoto Zourin, holds a prominent position as a model forest. Approximately half of Senryo Mountain is covered by a natural mixed forest of deciduous trees and natural cedar, with a section designated as a special seed-tree forest to preserve the Hachirou-Sugi mother tree. As a valuable forest that tells the history of the Chugoku Mountains from ancient times, this forest is used for the training and education of timber groups, government agencies and research institutions.

The company’s management philosophy is held in high regard beyond its borders – in November 1989, we were awarded the Emperor’s Cup at the Festival of Agriculture, Forestry and Fisheries in the forestry category.

Production Process

In the production of Yakisugi timber, the surface of the wood is traditionally charred. A responsible production process aims to reduce energy consumption, minimise harmful emissions and use resources efficiently. Nakamoto Forestry uses renewable energy sources such as solar energy or biomass to meet its energy requirements during the production process. Sawdust and waste from timber processing are converted into wood chips or pellets. Modern machinery is also used to reduce water and resource consumption.

Before charring, the timber must be dried to a residual moisture content of approximately 10–14%. Timber that is too moist cannot char properly – it cannot form a stable, long-lasting soot and charcoal layer. Instead of the energy-intensive kiln drying common in Europe and used by some Japanese manufacturers, Nakamoto Forestry has relied exclusively on air and sun drying for generations. Although this process can take several weeks to months depending on the season, it results in a gentler treatment of the timber, better timber quality, and significant energy savings compared with kiln drying.

The durability of Yakisugi comes from the controlled charring process – without chemical wood preservatives. On request, we finish the boards at our facility near Düsseldorf: using solvent-free oils based on linseed and tung oil, water-based stains, or – for heavily used interior applications – a water-based lacquer system.

We pay close attention to improving efficiency and reducing energy consumption in our production processes. In our kilns, for example, we use afterburner technology, which reduces natural gas consumption.

CO₂ Emissions: Production and Timber Storage

According to our Environmental Product Declaration (EcoLeaf, Type III, ISO 14025, no. JR-BC-2001E), the production of our Yakisugi generates 2.1 kg CO₂ equivalent per m². Separately, the timber stores approximately 15 kg CO₂ equivalent per square metre for as long as it remains in place.

We have decided that production in Japan using authentically and sustainably harvested Japanese cedar (Sugi), carried out by our experienced craftspeople using tried-and-tested tools and equipment and following generations of tradition, cannot be replaced by local production in Europe without compromising the quality of our products.

Durability – Considering the Product Lifecycle

A lifecycle assessment considers all the environmental impacts of a product or material throughout its entire lifecycle, including the extraction of resources, manufacturing, use, disposal, and potentially recycling or reuse. From this perspective, we can better understand and compare the overall environmental impact of a building material.

Yakisugi timber is known for its exceptional durability and resistance to weathering, moisture and pests. The charring of the timber surface makes it resistant to rot, insect attack and fungi. This means that Yakisugi timber generally needs to be replaced far less frequently, resulting in less waste and a reduced demand for new resources.

Japanese cedar is classified as a durable timber species. Yakisugi façades in Japan with service lives of 60 to 80 years are well documented – some have remained intact for over 100 years. The actual service life depends on construction, weathering conditions and maintenance.

Yakisugi stores approximately 15 kg CO₂ equivalent per square metre for as long as the timber remains in place. Due to its documented service life, it needs to be replaced far less frequently than conventional façade materials – reducing the demand for new resources over its lifecycle.

Certifications and Standards

Certifications and adherence to recognised standards play a crucial role in ensuring the traceability of our products.

Our forests and forest resources in Hiroshima Prefecture have held SGEC (Sustainable Green Ecosystem Council) certification since 2006 and PEFC (Programme for the Endorsement of Forest Certification) certification since 2019. Nakamoto Forestry, together with other forestry companies in the region, founded the Ota-gawa SGEC network to promote activities that create a circular regional society making use of local resources.

Our entire supply chain is also PEFC-certified. Nakamoto Forestry Europe received Chain of Custody (CoC) certification in 2020 (TÜV Nord 44 702 200728), covering the entire product chain from the forest through processing in Japan to delivery to our central warehouse in Europe.

Further certifications include Environmental Product Declarations (Type III, ISO 14025, no. JR-BC-2001E) for all our product lines, as well as our certification as a recognised forestry enterprise under Japanese forestry law for sustainable forest management.