Concrete does not grow on trees

Fortunately, a variety of engineered timbers, including CLT do. Why is this important? Because very soon we will have to start thinking very hard about just how much concrete we use in construction

Not that we can forget about running out of oil. But perhaps we should start worrying more about running out of sand.  That is the message of an alarming article in New Scientist recently.

"Modern life depends on sand, yet our supplies are dangerously low."

The problem, it seems, is that while sand appears to be plentiful, there are many different kinds of sand. And most of the sand is not suitable for the purposes where we use a lot of it.  After dredging sand for land reclamation, guess what is the most common end-use? It only takes a moment’s thought, and we realise that it is concrete.

"Between 60 and 75 per cent of the sand we mine goes to sate our hunger for concrete. It is tough, easy to work with and fairly cheap, which is why we use twice as much of it as all other building materials combined: about 30 billion tons per year. That is enough to build a wall 27m tall by 27m wide around the equator."

Apart from the idea that you might actually run out of suitable sand, there are also increasingly serious environmental and social impacts associated with sand mining.

To cut a long story short, we need to think about building in different ways, to cut down our addiction to concrete.

This reduction in the use of concrete in buildings is even more urgent when you consider the likelihood that we will probably need to reserve mass concrete for the heavy engineering in climate change mitigation, and for major civil works such as dams and road/rail infrastructure.

We have already built buildings where cross laminated timber has substituted for concrete slabs and walls. It has all kinds of advantages, ranging from extremely high tolerances in prefabrication, to much more flexibility and resilience for ad hoc modification.What is not to like?

The building knows who you are

and what you’re about to do.

This is not necessarily what you expect, when you query Google for 'the greenest building in the world'.  But as of January 26, 2017, that is what you get, on the slick website of Richard van Hooijdonk, self-styled professional keynote speaker and futurist.

He is speaking about 'the Edge', the Amsterdam headquarters of international consulting firm Deloitte, designed by PLP Architecture.  And to be fair, he makes a valiant case for the success of the building's combination of environmental responsiveness and embedded IoT (Internet of Things).

Dishonest structures?

One of the most powerful tenets of modern architecture was 'honesty' in structural expression.

The merits of this proposition were traced back to antiquity; for Bannister Fletcher,  the influential architectural historian, direct expression of the structural system formed the basis of classification for architectural form. In his view, Architecture evolved from 'trabeated' (post-and-lintel) classical, through refinements of the arch and vault in the Romanesque and Gothic. 

The mediaeval cathedral, searching for lightness in a heavy material, with its flying buttresses and delicate tracery, became the ultimate moral compass for this dogma. 

With the introduction of new materials such as steel and steel reinforced concrete, the range of possible building forms dramatically increased. These buildings came generally from the collaboration of adventurous architects and inventive structural engineers: the thinnest shells, the articulated rotating joints in 3-point portal frames, the most daring cable stayed suspension roofs became photogenic expressions of the spirit of modern times.  

Of course, things were never that straightforward.

A hint of what was to come could already be found in the most iconic of 'structure as building form', the Sydney Opera House. The famous shells are not shells at all, but arches leaning against each other – a small but important point in any discussion of structural honesty.

I am in no position to trace the origin or evolution of the alternative proposition, which may be simply stated as:

..... in fact the most important function of structure is merely to hold up the planes and surfaces which enclose space.  

Suffice to say that such a less moralistic attitude was a convenient starting point for the true revolution in architectural form and space. 

Arguably, the greatest exponent of the new freedom was the late Zaha Hadid.  I might dislike many of her parametrically generated squishy building forms, but her Riverside Museum in Glasgow is a masterful exercise in making lots of little sticks work together  to produce large spatial effects.  Ironically, these folds and twists teasingly suggest higher orders of structural rationale.

The pragmatism in structure and construction quickly spread to more humble buildings.  

The lower pair of images in this post are of a small regional community library at Moe, Victoria.  In the hands of FJMT Architects the formal expression is of simple stacked boxes, but masterfully clad in beautiful materials. The image of the building under construction makes it clear just how ordinary is the construction under the extraordinary skin.

My personal reaction to this liberation from the moral imperative of honest, legible structure, is ambivalent.

As an architect, I welcome the freedom in design, which lets you assume that anything is possible. 

 As an observer of what I call journeyman architecture (such as medium rise apartment buildings), I see mainly a very particular extrapolation of that freedom – the almost universal use of flat plate construction.  I wrote in my blog post The new rational architecture that this can lead to new and exciting typologies, or more often to a cavalier lack of discipline in floor layouts.

As a teacher of architecture, I became quite uncomfortable. In my dealings with students, I found that it became much more difficult to have meaningful, rational discussions about design quality and design principles.

I used to ask my students to "draw me the building, not the cardboard model of the building".  But, that favourite aphorism lost all its moral authority, once the actual buildings they saw around them more and more resembled stacked shoe boxes with invisible structure.  And some nice materials pasted on as decorative veneers.

Wonderwood

The gift material that keeps on giving

Stronger than steel? Transparent? Carbon sequestering? Positive embodied energy?  Remediative waste stream?  Sounds like a material from Marvel Comics.  But it's very likely all true.

I have written specifically about modified timber before.  In Designer materials: Helping nature? I summarized the history of treated timber, culminating in acetylated wood modification. That process protects wood from rot by making it "inedible" to most micro-organisms and fungi, without making it toxic. It also greatly reduces the wood's tendency to swell and shrink, making it less prone to cracking and ensuring that it requires dramatically reduced maintenance.  But the most surprising sustainability bonus of the product is that one of the waste products of the acetylation process is acetic acid, which is a valuable feedstock in other industries.  You can see where this is going.......

Engineered timbers are a whole other field of radical advances, including Glue Laminated Timber (glulam), Laminated Veneer Lumber (LVL) and at least another dozen products which allow designers to consider how they may substitute a renewable resource for other structural systems. But what would you be able to do if the timber itself were stronger than steel? 

That is now a fair question.  Judging by the announcement from University of Maryland, where scientists have demonstrated a wood densification technique, described in Nature, which has led to the creation of a material that is 12 times stronger than natural wood, as well as 10 times tougher.

According to Dr Liangbing Hu the timber material could be a competitor to steel or even titanium alloys, and could be used in cars, airplanes, buildings – any application where steel is used. “It’s also comparable to carbon fibre, but much less expensive.”

Earlier, Swedish researchers had already demonstrated a related technique for removing lignin from wood, to produce a a transparent material which they say could be used as windows, facade elements and even in solar panels.

“When the lignin is removed, the wood becomes beautifully white,” Professor Berglund said. “But because wood isn’t not naturally transparent, we achieve that effect with some nanoscale tailoring.”
This is done by impregnating the white porous veneer substrate with a transparent polymer.  The wood sample had a transmittance up to 85 per cent – comparable to glass.  A haze of 71 per cent is claimed to make the material attractive for solar cell applications, as light would be “trapped in the solar cell for longer”.

The researchers suggest that the modified wood could also be used for semitransparent facades, where both light and privacy are needed.  For these applications, the material "offers excellent mechanical properties, including strength, toughness, low density and low thermal conductivity.”  One on the note: given recent bad experiences with flammable facade materials, it is curious that no mention is made of flammability.

The University of Maryland group has also produced transparent – or more properly, translucent timber sheeting.  They report that their transparent wood provides better thermal insulation than glass and lets in almost as much light at glass, though without any glare – providing more uniform and consistent indoor lighting.  But to me, the most exciting news if it's true is the following claim.  Lead author Tian Li reports:

“We also learned that the channels in the wood transmit light with wavelengths around the range of the wavelengths of visible light, but that it blocks the wavelengths that carry mostly heat.”

Think about it. The reason why glass has been such an almost mystical material is that it lets in short infrared (the heat part of the solar spectrum), but is effectively opaque to long infrared (the heat would normally perceive at earthly temperatures). That is the original 'glasshouse effect' so useful for passive solar heating.

But there has always been a price to pay, where the same effect is the major cause of overheating in summer.  Transparent wood seems to have almost the opposite property of keeping the thermal loads down, while providing lots of daylight. This would be a boon any overheated climate.

The trigger for this post came from three articles in The Fifth Estate:
See
Transparent wood: the future of windows and solar panels? 
Transparent wood trumps glass on energy efficiency and light.
and
See ya steel: scientists create wonder material from wood
The research has been published in Advanced Energy Materials.