In 2022, Architects CAN (ACAN) hosted a free webinar on using local timber. ACAN is a network of individuals within architecture and related professions taking action to address the twin crises of climate and ecological breakdown.
The ACAN Natural Materials Masterclass on 'Specifying, Growing and Using UK Timber' featured expert speakers including Tom Barnes. Tom is MD of Vastern Timber, and he led the team developing Brimstone, Britain's first thermally-modified homegrown wood.
Read on for a summary of Tom’s talk.
To see the full presentation on YouTube, click here.
Brimstone came about because much of the wood that we have growing in our woodlands is not deemed to be desirable by the industry anymore.
There's lots of species growing in our woodlands that don't have a use, and therefore they don't have value, and that means that woodland owners can't sell them. That means they don't have the money coming in to do the management, conservation work and replanting that’s needed for woodlands to thrive. The problem was how to give value to these timber species that we have in our local woods - and that really is where Brimstone came from.
The availability of wood in this country is likely to fall in future. The predictions are that the surface area of buildings is going to double by 2050, and consumption of wood is predicted to Triple!
The trouble is, trees aren't going to speed up for us… particularly slow growing trees. There's species we have used in the past and that we still use now, that take hundreds of years to grow. Some tropical species like Canadian Cedar can be up to 400 years old. An oak tree that I could just about get my arms around would be 200 years old.
It doesn't matter how you define the word sustainable, if we want to use more wood we cannot sustain the use of wood that takes hundreds of years to grow. But often fast-growing woods don't have the properties we want, they tend to be soft, they tend to be less stable, they tend to be non-durable.
So what if we could take a tree that has taken decades to grow and we could make the wood from it behave like it has taken centuries to grow, without using any noxious chemicals. I think that would be pretty cool, and in fact, that’s what modified wood is all about.
At Brimstone we decided to go down the route of thermal modification because you can pretty much modify any wood. Some species work better with thermal modification than others, but with impregnation modification you can only really use a very limited number of species. The most popularly used for wood for impregnation modification is radiata pine from New Zealand. That means bringing the wood halfway around the world before we use it.
The great thing about thermal modification is that we can use locally grown wood.
We're extremely proud that in January we built the first thermal modification plant in the UK. And we have plans to install another larger one.
The capacity of our plant is around 1000M3 per year. That’s equivalent of 31Km2 of cladding.
We produce Brimstone from local Ash, Poplar and Sycamore, sourced within 100 miles of our plant in Wiltshire.
Brimstone has Class 1 durability, and the process results in a huge improvement in dimensional stability in the timber. Thermally modified timber is a popular choice for cladding, decking and joinery. And only heat and steam is used in the process.
At Vastern Timber we've worked with local wood for four generations, and we’ve got no interest in trying to import wood from further afield.
I think for me certainly the essence of 'sustainability' must include an element of localism, and there has to be scale. Scaling a plant like ours to fit in with the availability of raw materials around us is really important.
The vast majority of Brimstone at the moment is going into cladding, that recently has been driven by the fact that one of the staples of the cladding markets, Siberian Larch, is now basically illegal, and Canadian Cedar is now very expensive.
It has prompted many contractors to contact us and say… “we've specified Siberia Larch or Canadian Cedar - what else can we use?” and we take great pleasure in saying “how about you use something that's grown just down the road?”
This EPD is from a few years ago and it’s important to recognise that it includes data from before we had the thermal modification plant here, we were taking the material to France to have it modified and bring it back, so the EPD when it is renewed next year, I think, will look a whole lot better.
But it’s really important to focus on the bad side of the emissions and be honest about them. It’s absolutely key this whole conversation is honest, and we all need to be honest about what the bad impact of making a product is.
I think we were one of the first companies to split out the biogenic carbon and the fossil based carbon in the EPD and just put the fossil based carbon there front and centre and say “look this is the impact” and the story is how can we reduce it? That is what we're doing at the moment by bringing all of the manufacturing onsite. We’re doing our absolute best to run this plant on renewables as soon as possible.
We are also looking at sequestered carbon. It is important to consider the idea that wood is a carbon store, but for that to be a valid argument the wood has got to be in use for a long time. It’s not really a valid argument if the wood is going for biomass or into a very short-term use like animal bedding or even fencing that barely lasts more than five years.’
We can modify local wood to make it last a whole lot longer.
The Brimstone life cycle is that the tree takes about 50 years to grow, and the product should last about 50 years in service. It’s our mission to keep that wood in use for as long as possible.
This beautiful renovation project is one of a kind. Once an old threshing barn, it has been transformed into a family home, studio and wildlife haven by landscape architect and owner Toby Diggens.
Build It magazine presents Brimstone the award for 'Best Cladding.'