Part of the decline of The Economist, aside from the fact its employees write drivel, is its wholesale adoption of the environmentalist religion. With their latest video they seem to be plumbing new depths of woo-embracement:
Can wood replace concrete and steel as the go-to building material? pic.twitter.com/ivLd0dooxY
— The Economist (@TheEconomist) July 18, 2018
The answer, of course, is no: wood has been used as a construction material since the dawn of time, and in the modern age there is probably not a thing we don’t know about it. Concrete and steel replaced wood for very good reasons, and unless wood has undergone some revolutionary step-change (e.g. trees grown with carbon-fibre grafted into them), those reasons still apply. If it made technological sense to use wood instead of steel, people would be doing it. If it made economic sense, the same would be true. But let’s take a look at the video (I’ll paraphrase rather than write the whole transcript).
0:25 The world’s population is increasing, by 2050 it will be 10bn most of whom will be living in cities in skyscrapers with a large carbon footprint.
The video shows Tokyo and other developed world cities, but almost all that population growth will come from Africa. Are they going to be living in high rises? Having seen the sprawling shanty towns of Lagos in person, I doubt it. And if “carbon footprints” are a problem, maybe its time to stop subsidising that population explosion in Africa? One of the main reasons Nigeria’s population is exploding is the lack of reliable electricity, which in turn is a direct result of corrupt government practices. What I’m trying to say is, if increasing populations are a concern, building materials are an odd thing to focus on.
0:30 Our view is all buildings should be made from timber, and we should look at steel and concrete as we do diesel and petrol.
I have no idea who this chap is, but he’s looking at a Landcruiser and trying to say a horse would be better. I suspect he’s saying this because his salary depends on it.
0:44 I think it’s realistic someone will build a wooden skyscraper in the coming years. There is a lot of potential that is unrealised for using timber at a very large scale.
It’s as if engineers are unaware of wood’s limitations in compression. Hell, even the Romans knew over a certain size you had to use stone and concrete.
1:00 Throughout history buildings have been made of wood But it has one drawback, it acts as kindling.
Don’t ever say Economist videos aren’t informative.
1:32 If concrete were ever to arrive as a new material on “Dragon’s Den”…but then you say we need a whole new fleet of trucks to move it around…
You can tell this guy is an academic. Firstly, there are transport costs associated with wood; they don’t grow trees on potential building sites and wait a hundred years. Secondly, the cost savings associated with using concrete obliterates the additional cost of needing specialist concrete trucks. It’s one thing to play devil’s advocate for some future hypothetical, but this guy is doing it for something that’s already happened: he’s already been proven wrong.
1:51 I don’t think it would be a compelling case.
The richest man in Africa is a Nigerian called Aliko Dangote; the bulk of his wealth comes from his owning Africa’s largest cement company. The invention of concrete revolutionised construction, and made an awful lot of people incredibly rich. But here we have an academic saying if it came along nowadays, nobody would be interested because you need to add steel and buy some specialist trucks.
1:58 Concrete and steel are costly to produce and heavy to transport.
Compared to what? This is like saying the weather is good.
2:05 Wood, however, can be grown sustainably and is lighter than concrete.
Weight doesn’t matter much in buildings, because they tend to be stationary objects supported by the ground. You also have a lot of glass curtain walling these days. If weight is a concern you use steel – as the Manhattan skyline nicely demonstrates. Insofar as transportation costs go, aggregate can be shipped cheaply in bulk from anywhere, and you can install a concrete batch plant on or near to the construction site. A someone who lived in Dubai during the construction boom, I saw a lot of this.
2:07 And crucially, as trees grow, they absorb carbon dioxide from the air, locking it into the timber.
This is crucial? Not to construction considerations it isn’t. If you want trees to absorb carbon dioxide then plant more trees, but to put this forward as an advantage for using wood in construction? You might as well say forests are nice places to walk a dog. In any case, unless these buildings will stand for centuries, at some point the wood will rot or burn releasing all that carbon dioxide into the atmosphere anyway. Why not leave the trees standing?
2:18 One study showed that by using timber to construction a 125-metre skyscraper could reduce the building’s carbon footprint by up to 75%.
One study…could…by up to. Well I don’t know about you, but I’m convinced! Note all this assumes a building’s “carbon footprint” is something we should be concerned about.
2:42 Wood isn’t strong enough to build high, but engineers have come up with a solution: cross-lamination.
2:45 It’s cross laminated so layers of wood are glued at 90-degrees to one another.
3:17 But what about fire?
They demonstrate how a skyscraper made from wood will withstand a fire by holding a blowtorch to a piece of plywood before claiming it will extinguish itself after losing “some structural mass”.
3:25 We’ve actually seen steel roofs collapse in fires when wooden ones have not.
Assuming this is true, this is an argument for making sheds from wood, not skyscrapers.
3:52 Once these wooden panels arrive on site we’re building a floor a week.
Right, but it’s essentially a 5-storey plywood box. Are you sure this method is going to work for skyscrapers with 50 plus floors?
3:57 This is maybe twice as fast as concrete.
The guys in Dubai were pouring a floor every few days. I’d like to see how fast these wooden panels go in when they’re a hundred metres above the pavement.
4:23 Andrew and his collagues designed Britain’s first wooden high-rise apartment block.
It’s ten floors, hardly high-rise.
4:51 As yet, nobody has used CLT (plywood) beyond 55 metres.
The building they refer to is Brock Commons tower in Vancouver:
The structure is concealed behind drywall and concrete topping, mainly to comply with the accepted fire-safety codes and consequently speed up approval from building authorities.
So it needs concrete to stop it turning into a matchbox, incinerating everyone inside. But wait, what’s this?
Due to concerns about structural stability, the American Wood Council and the International Code Council currently limit wood structures to a maximum of six stories above grade, depending on occupancy type.
For good reasons, I’d imagine.
To reach its height of 18 stories, Brock Commons used a slightly different approach. It follows in the shoes of the supertall skyscrapers we’ve seen cropping up across Asia and the United Arab Emirates (UAE), which use a central structural core to take the stress off of the building’s exterior.
Oh! What type of central core?
Two concrete “trunks” on a concrete podium form the core of the structure, with the rest of its 18 stories being constructed of cross-laminated timber (CLT) flooring and glue-laminated timber (GLT, or glulam) columns.
So this groundbreaking tower block which demonstrates the viability of wooden skyscrapers is held up by two, bog-standard concrete cores? The Economist never mentioned that.
This entire video is basically a puff-piece for a London-based architectural firm with its eye no doubt on government monies earmarked for eye-catching green “solutions”. Wood can be used effectively for construction, but it has severe limitations which are well known: warping due to heat, rotting due to damp, termites, separation of lamination with time – and the ubiquitous fire hazard. I’d love to see how well this Brock Commons tower is holding up in a decade’s time, and hear it from the poor sods who have to live in it, not the architects. This is before we even address such issues as increased land use to grow the trees, not to mention the wastage. The good thing about steel and concrete is it can be moulded to the shape you want without wastage, but wood has the tendency to be grown tree-shaped and from there you need to chop, saw, shave, and sand it into something useful – all of which creates mountains of waste product (when I was a kid, timber merchants used to give away wood shavings and sawdust for free). So what happens to that?
How many trees occupying how much land are needed to build a 100m building, and how much waste is involved? And how much chemical treatment does the wood require? Some numbers would have been nice, but this is The Economist: when it comes to the environment they sound more like The Watchtower.