Yoroi - deep burned bamboo planks with fire class B - with CAT 1 data in NMD
During his travels through Japan, architect Pieter Weijnen became extremely enamored with the way black-fired wood is used in Japan for facades of homes and buildings, among other things. In 2012, he decided to bring the sustainable product to Europe. He mastered the traditional Shou Sugi Ban technique and added modern technology. Meanwhile, the company Blackwood | Shou Sugi Ban has a production process that can burn highly controlled and high-quality wood planks according to the Shou Sugi Ban principle. The product Yoroi is one of the products in the collection. This is a high quality bamboo board that meets a fire class Bs1-d0 after burning. Since the fall of 2023, this product has been listed with category 1 data in the National Environmental Database.
We call for this interview with Paul Vriend, sales manager at Zwarthout | Shou Sugi Ban. He talks about how the one-man company that founder Pieter Weijnen started with is now doing projects around the world with a team of 12 people.
“Those projects range from cladding the facades of homes and fire stations to supplying burnt wood for large school buildings, apartment buildings and CO2-neutral distribution centers. In the Netherlands and the rest of Europe, and sometimes beyond. All from our production site in Leersum.”
Zwarthout | Shou Sugi Ban
Paul Vriend
Century-old technique
The technique of burning wooden planks - Shou Sugi Ban - has been around for centuries. This involves burning softwood on one side by binding three planks together into a chimney and lighting a fire at the bottom. The process of controlled burning of the planks gives them a fire-retardant coal layer and, when used in building facades, they require no maintenance.
“This is because living organisms no longer have a breeding ground on the planks, so no further processing with chemicals is needed to counteract that. The planks also retain their color because charcoal is UV-resistant. As a result, the planks remain black throughout the product's life cycle.”
Producing larger volumes
Zwarthout | Shou Sugi Ban has been looking for optimizations in the production process from the start of the company.
“A disadvantage of traditional technology is that you can never produce larger volumes at once. That is why we worked in Leersum on the further development of several kilns, so that in addition to very high efficiency, high numbers of square meters can also be fired in a highly controlled manner. In early 2023, we took the newest kiln into operation.”
“To get where we are today, the development of these kilns has been a continuous process for the past 12 years. Our fire masters can now burn ample quantities per day, so we can also supply large projects with the Blackwood | Shou Sugi Ban products. With the latest kiln, we can control and thus control the temperature, oxygen content, speed and cooling even better. Quality is reflected in our products.”
Each product a unique appearance
More than 50 different types of wood have also been experimented with in Leersum. “Then you notice that most of the wood types do not come out of the kiln beautifully. It is not necessarily the case that the hardest types of wood give the best charcoal layer or vice versa. We tested a lot with that in recent years and continue to do so, both in terms of technique and the types of wood to use.”
“We are now working with five wood species that we have very good experiences with. Accoya, from a fast-growing coniferous tree. Fraké, from the fast-growing Limba from Cameroon. FSC® thermally modified bamboo from China. Pinus Radiata, a fast-growing pine from FSC® certified forests in New Zealand. And wood from the Douglas fir, from FSC® certified European forests of the Forestry Commission.”
Depending on the wood species, the finished product takes on a certain structure of crackle. It also happens that the wood planks are brushed after burning. “Then you get to see the wood structure again.”
LCA for deep burned bamboo planks
For the bamboo product called Yoroi, Zwarthout | Shou Sugi Ban recently commissioned a life cycle assessment.
“We find that this product is in high demand because it meets fire class B, with no further processing required after burning. The fibers on the surface of the board have already been burned and therefore will not reignite quickly. The combination of material and technology ensures that no maintenance is required to maintain the fire class. No substances can leach out during its lifetime either, which is a huge advantage.”
“As the focus is increasingly on sustainable and circular construction, it is good to show the environmental impact of our product. So that decision-makers can make informed choices. Architects want to know which products they can use for this purpose and how they perform environmentally compared to other products. That's why we decided to have an LCA made and have this product with category 1 data included in the National Environmental Database.”
Instructive process
Getting such an LCA done was quite a process, Paul explains. “We are a small and young company with the necessary experience, but we had never done this before. Of course we involved an LCA specialist, but even then you are faced with many questions that you never really asked yourself. We also learned a lot from this, for example about the way we package our products. How much plastic do we actually use and how much impact does that have? You become very aware of what you do and start thinking about how things can be done differently. We now use thinner plastic and plastic with more air, so we end up using a lot less plastic.”
No more assumptions, but hard data
Blackwood | Shou Sugi Ban is pleased that there is now hard evidence of the sustainability of their product.
“No more assumptions, but data that show how our production and our product scores. For example, people still sometimes think that the combustion process is very environmentally polluting and that we consume a lot of gas. That is certainly not the case. The gases released during burning are captured in the furnace and ignited elsewhere with oxygen. As a result, our gas consumption is minimal. We are not yet CO2 neutral, but we don't emit much either. We are very conscious of it in all areas.”
To fill the NMD with as much category 1 and 2 data as possible, we encourage producers and manufacturers of building materials in providing this data. We do this with a scheme that allows you to be reimbursed €2,500 for having an LCA made.
Being able to compare apples with apples
As a next step, Blackwood | Shou Sugi Ban plans to have a life-cycle analysis done of products made from Douglas fir as well. “We expect to score even better for those products. Douglas fir wood comes from close by, from Europe, and is lighter in weight, among other things.”
Paul hopes that producers who are not yet in the NMD with their products will soon follow suit. “It's a good tool to monitor ecological impact. This is already an important issue and will only become more important. It's nice when architects and builders can compare apples to apples when making their choices.”
Category 1,2 & 3, how was it again?
The National Environmental Database collects environmental data on building products. Those data describe for each life stage of the product what effect the building product has on resource depletion and what toxic emissions are released. The database is the central data source for calculation tools used to determine the environmental performance of construction works. In the National Environmental Database, we distinguish three categories of environmental declarations of products.
Category 1
These are verified, proprietary data. They are the property of the manufacturer.
Category 2
These are verified, industry/sector-specific data. They are owned by the industry.
Category 3
These are untested, generic data prepared by LCA experts. These category 3 data represent a fallback option for when maps of this product do not yet exist. These data are less sharp, which is why there is a markup factor on them of 30%.
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