Wood’s popularity as a sustainable building material has shot up in recent years, but how does it stack up in the industrial and logistics sector?
It’s light, low on carbon and insulates well: timber’s properties as a sustainable building material are well documented - and amid today’s intense pressure on real estate to decarbonise it is grabbing industry attention.
In recent years, the use of timber has been gaining ground mainly in the residential and office sectors, where besides its carbon-reducing qualities it is sought after for its aesthetic and so-called biophilic benefits – with recent studies suggesting that wood structures and finishings contribute to the health and wellbeing of building occupants.
Its use in industrial and logistics warehouses, however, has so far been limited mostly to external cladding and facades. But that is set to change, according to Peter Farmer, a transport design expert at international architecture and master planning firm Benoy.
Farmer, who has over 25 years’ experience working on various design aspects and construction techniques in the rail, road, aviation and logistics sectors, says demand for timber warehouses is increasing as both investors and end-users discover its sustainability benefits. ‘Some of our clients are now coming to us and saying: can we have a timber framed building because it’s more sustainable,’ he says.
Investor push
The driver behind this demand is a desire to reduce carbon, whether to meet increasingly stringent ESG reporting requirements or to enhance corporate reputations. ‘The push is coming from investment funds and in some cases the end-users,’ notes Farmer. ‘There are people in those funds who genuinely want to reduce carbon in their buildings, but it can’t be completely removed from the fact that it’s going to be good for their investment profile to be seen to be developing reduced carbon buildings.’
Demand aside, how suitable is timber for large buildings such as big box warehouses? And, how sustainable is it compared to other materials such as steel? The answers are not so clear-cut, particularly if factors such as material sourcing and supply, recyclability and maintenance are taken into account.
Wood captures carbon and performs well as spanning for the large portal frames typically used in warehouses. But it is difficult to reuse. Explains Farmer: ‘Once you have used timber in a portal frame it is difficult to deconstruct and use again. It is invariably chipped and can be used in particle board-type construction, but once it has been used in that, there’s very limited use beyond that and it tends to go to compost or biomass – which then puts the carbon which those trees have captured and held within the warehouse for, say, 30 years back into the system.’
Steel is energy-hungry in production and therefore high on carbon, but a very easy form to construct and well suited to large structures. A key advantage is that it can be recycled almost endlessly, says Farmer. ‘With a steel frame, you can take it down, recycle it and build new steel structures – in theory ad infinitum.’ Using eco-friendly recycling methods, such as solar-powered instead of gas-fired furnaces, would boost steel’s sustainability credentials, he points out. ‘If a steel frame is taken down and reconstituted into new steel components using an electric furnace, I can’t say it’s completely carbon free but it’s significantly lower.’
But a major obstacle to this approach is that the infrastructure is simply not in place, says Farmer. ‘There are very few steel recycling plants in the UK and indeed across Europe, so we don’t have that option.’ Coupled with tight supply of raw steel, this is forcing firms like Benoy to look at alternatives.
Hybrid structures
For now, the company, which operates out of studios in the UK, Asia and the Americas, is looking to go hybrid in many cases. ‘Rather than pure timber frame structures, we’re actually starting to look at hybrid structures – which in my view is the most sensible way to go because steel is very good in tension and complex node connections and timber performs well when it’s spanning,’ says Farmer.
‘Particularly for warehouses, a key challenge is how to produce the same performance criteria in terms of span and column-free environments with timber as you would get in a steel frame as clients are asking for it.’
Drawing on his long track record in multiple sectors, and working with other consultants, the materials and design specialist is developing what he calls a ‘check list’ to ascertain how to best match clients’ sustainability demands with the most cost-effective solutions.
With this in hand, more considered decisions can be taken, he believes. ‘So, rather than opt for a timber frame from the outset, you look from the ground up at all the other aspects. If, within your investment equation you’re able to pay another 5% capex to get a timber frame, you need to convince yourself that that’s the right place to spend it, or would it be better spent elsewhere, such as reducing the amount of aluminium, steel or cement or improving some of the MEP (mechanical, electrical and plumbing) systems.’
Where timber is used in cladding or facades, maintenance poses its own set of challenges. In theory, wood used on the outside of a warehouse should be stripped and recoated every 7-8 years. By contrast, metal cladding has a life span or around 25 years before needing maintenance. In practice, however, users often carry out only the most necessary maintenance of their buildings as ‘it isn’t in their business model’, says Farmer. ‘Most companies are in a competitive market, they maintain their buildings as much as they need to, but they probably don’t want to be saddled with a building they need to strip and repaint every seven years, no matter how sustainable they want to be.’
Supply shortage
Apart from the intrinsic properties of individual building materials, another key challenge is their supply. As the use of timber in construction soars, not only in Europe but worldwide, concerns are being raised over how to service this burgeoning demand in the long term.
Estimates from the World Bank predict that global demand for wood products is set to treble in less than 30 years, driven primarily by higher living standards, greater urbanisation and greater use of what is increasingly seen as a more sustainable building material.
The UK imports over 80% of its wood requirement, mainly from Sweden and other Scandinavian countries, making it one of the world’s biggest importers, according to Confor, the trade association for the UK forestry industry. This means that only around 20% of its wood requirement is grown domestically, a fact which also worries Farmer.
‘Even if we were planting trees at the same rate as wood consumption is increasing, those trees aren’t going to come onstream for a few years,’ he says. ‘My personal concern is that we are going to reach a tipping point where the use is outstripping the supply of trees.’
While he has no doubt that he will ‘in the next couple of years’ build a warehouse with a timber frame, Farmer says the supply constraints give cause for reflection on how to deal with resource scarcity. ‘There is a part of me that starts thinking, is it better to use this timber in a home where it’s more visual and tactile, and its benefits are more immediate, than in the roof of a warehouse where very few people will see it?’