Monday, 12 March 2018

Green security

Developer buys up nurseries to secure plant supply for future builds

I will resist the temptation to joke about putting planter boxes in front of entrances to slow down car bombs.

Sometimes you come across a little bit of news that surprises you, and makes perfect sense.
Romeciti, a local Sydney developer have just announced that they have acquired two plant nurseries, so that they could guarantee the supply of mature plant material for their building projects.
According to a spokesman for the company, since Romeciti was formed it has always been focused on creating 'green cities':
"We feel that a healthy community includes having access to green spaces, as it has been proven to bring a sense of calm and wellness in this busy modern world. We feel this growing market desire for a green environment is just a natural shift by educated buyers who recognize the importance of greenery in a long-term residence."
It is really easy to dismiss that kind of talk as current zeitgeist marketing hype.  Until you see by their actions, that they mean it and they are prepared to invest in it. They also add significantly to their credibility by emphasizing that their investment is not just in assuring the plant supply, but also in building up their expertise in choice and maintenance of those plants.

Obviously, not every developer can follow this approach. But the initiative is scalable, especially if we had government brave enough to participate.

Congratulations to Romecity.
Read the original article in Architecture and Design, here.

Wednesday, 28 February 2018

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?

Friday, 16 February 2018

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.

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 long 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 counter proposition:
..... 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. 

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 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.

Thursday, 15 February 2018


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:
Transparent wood: the future of windows and solar panels? 
Transparent wood trumps glass on energy efficiency and light.
See ya steel: scientists create wonder material from wood
The research has been published in Advanced Energy Materials.


Monday, 29 January 2018

How do green walls actually work?

Greenery within the city has a whole range of potential benefits, from favourable impact on thermal comfort and energy consumption, improvements in air equality, establishing or reconnecting local ecologies, to providing passive and active recreational space. How much of these benefits, and at what financial and resource cost, depends on how the plant material is provided – in conventional parks, planted roofs, or green walls.

This brief note is not intended to be a definitive discussion of these benefits, but I thought it might be helpful to expand my previous post Questioning green walls.

Green walls are definitely the most ‘extensive’ method of providing plant material in urban settings. The terminology is borrowed from how green roofs are categorised, where ‘extensive’ means very shallow and limited growing media, while ‘intensive’ refers to deeper and larger volumes of soil. But the more colloquial meaning of the word ‘extensive’ is also relevant when we are discussing taller buildings: the area of wall generally far exceeds the available areas of roofs, and landscape areas at ground level.

Green walls therefore both resemble other settings, and have some significant differences in how they work. For instance, because of their orientation, green walls would contribute less to mitigating the urban heat island effect, than do horizontal areas of planting.


Heating and cooling energy 

The contribution of green walls to the cooling energy balance of a building is complex.  But to describe it simply, they:
  • provide external shading, thereby reducing the direct and diffuse solar load;
  • present a cool radiant surface facing inwards, increasing the potential for desirable heat loss in summer by outward radiation;
  • trap a cushion of air against the façade. This protected boundary layer is evaporatively cooled by transpiration from the leaves, in turn significantly lowering the conductive heat gain on hot days.
It is important to note that much of the benefit in summer is intimately related to the water consumption driving what is effectively a complex direct and indirect evaporative cooling system.

The protected boundary layer next to buildings can also reduce conductive heat loss in winter, but because it’s working in opposition to the evaporative cooling, this is likely to be a much smaller effect than the summer cooling contribution.


Air quality

Plants can help to reduce air pollution, by a combination of filtration to take particular to matter out of the air, and various chemical reactions to reduce the concentration of gaseous pollutants. It is well accepted that greenery in interior spaces has measurable benefits for well-being, by improving air quality. Not to mention psychological benefits, which have also been extensively studied..

But there has been some credulity with respect to claims that exterior green walls have similarly measurable outcomes for air quality.  

So it comes as something of a pleasant surprise that as far back as 2012, the journal Environmental Science and Technology reported a study which seems to support those claims.  Scientists at the Universities of Birmingham and Lancaster (UK) not only argued that by ‘greening up’ our streets a massive 30% reduction in pollution could be achieved, but also that if we are considering urban canyons specifically, green walls out-perform street trees and other configurations of greenery. But this optimism comes with an important caution:

All of this requires, of course, that the plants don’t expire in the extreme environment of today’s cities. Dr Tom Pugh, from Lancaster University, UK, said: More care needs to be taken as to how and where we plant vegetation in our towns and cities, so that it does not suffer from drought, become heat stressed,  vandalised, or interact negatively with other aspects of our urban areas, and can carry out the very important job of filtering our air.’

Friday, 26 January 2018

Questioning green walls

It had to happen sooner or later: green walls are being questioned.  Are they really a good thing from a sustainability point of view?

For anyone who has harboured any thoughts that external green walls on high-rise buildings might be one more expedient combination of sustainability rating 'bling' and marketing hype, a recent post in the Fifth Estate is compulsory reading.

The article quite fairly sets out the issues to be considered.  On the positive side, there is aesthetic value, heating and cooling load reduction, and contribution to mitigating the urban heat island effect.  On the negative side, focus is primarily on the overall cost, both financial and in resources, especially in maintenance. 

Put as simplistically as that makes it sound like negative criticism is short sighted, and another example of the ‘race to the bottom’.  But as usual, the devil is in the details.

First and foremost, the discussion is about a very particular type of green wall – exemplified by the world’s tallest example at One Central Park in downtown Sydney, the iconic high-rise residential tower by Jean Nouvell and Patrick Blanc.  This kind of green wall is effectively a relatively thin ‘veneer’ within the façade – essentially a curtain wall otherwise dominated by glazing.  Notwithstanding the skillful choice of species of plants borrowed from natural cliff-like ecologies, this typology of green wall is inherently fragile and demands high maintenance. The Fifth Estate article hints at the idea that this increased commitment to maintenance might be viewed positively as a contribution to social sustainability – I assume by creating jobs.

But there are other ways of greening buildings. Most obviously, roofs are friendlier surfaces, though the higher the building the smaller the proportion of roof to overall building surface. 

More usefully, facade planting can happen in robust configurations such as bigger planting boxes. We have plenty of precedent for these more traditional artificial landscapes – probably the best known is WOHA's Park Royal complex in Singapore.  Arguably the only barriers to employing them more often, are short-sighted restrictions such as indiscriminately applied floor space ratios.

Ultimately, I agree with Dr Paul Osmond, director of the Sustainable Built Environment Program at UNSW, when he says that the value of green walls over their lifecycle is still an open question:
“From a service life perspective – from design, installation, maintenance, replacement of plants, water systems and even decommissioning – no one has really explored that.”
As usual, I do not try to reproduce the original article. 
You should read it here.