After a lifetime as a town planner, with all usual extrapolations of trends into the future, I’ve found that the crux of the matter is (and has always been) a fair discussion of the future as we can see it now. So much of the future has been defined by choices already made and opportunities long since foregone – not to talk about the stupid 25 year horizon of our development plans, based on already made choices. Facing a future with “less abundance” of finance and energy needs more than a simple Monopoly board and the few choices the playing cards indicate. We are not in times of self-full filling prophesies of ever growing GDP any longer, a fact you probably realized already.
We are now in times when cost of manufacturing and energy needed must be seriously taken into account as well as the carbon footprint the construction industry is creating. Although the industry and many in the development professions (incl. real estate) seemingly treat this as a taboo subject, we have no other choice.
My intention is to put some attention to building materials that are more “medium tech” than the old fashioned “low tech” technique in use at the moment. I’ll do so but first some words about the impassible construction methods we are currently (and traditionally) using and the consequences of that.
Let us take a look at an UK paper (from Google) under the headings they use, starting with
Climate Change - Building use in the UK contributes about 50%of the UK’s CO2 emissions and construction contributes another 7% (figures from 2004). The main base performance criteria for energy efficient buildings all concern the thermal performance of the building shell where most of the CO2 gains can be made.
Thus my column in Boidus 01.02.2012 – Embodied Energy - and we received not a single comment! The 7% can be reduced depending on materials and design, of course also on building methods and technique’s applied. The paper goes on:
The fact is that if we are serious about climate change then we need to stop playing games with technologies which do not delver real CO2 savings. The real challenge in this area is the refurbishment of existing buildings (soon very imminent here as well as those being built right now). However, it would help for a start if we also produced really energy efficient buildings (and we are not doing this).
Waste - The waste going to landfills from the construction industry in 2004 was about 100 million tons. This is more than 3 times the amount of domestic waste collection (28 million tons)….and this is equivalent to one house being buried in the ground for every 3 built….and the calculations do not take into account an extra 25% energy for waste.
These are figures for 2004 and UK. But looking around in the un-built areas of Gaborone and the way we are knocking down, actually crushing, so called illegal buildings, I’m sure we are close to the UK figures (if turned into percentage). This doesn’t augur well regarding the coming re-development of older parts in our City.
The report goes on highlighting “Resource Use” and points out that a large proportion of construction materials are imported there, as here. And transportation of building materials over long distances is not only expensive (in the future, maybe unsustainable) as well as increasing the CO2 transmissions.
The report ends with a note that the construction industry has a big impact (probably the biggest of all industrial sectors) on the carbon emission. And we know from other studies that the simple curing of concrete stands for +5% of the total carbon emissions to the atmosphere.
In short, there is high time to discuss our building and construction methods – and there are actually much better alternatives than the use of concrete blocks and cement, for instance. I will point out such alternatives in the following but first a typical experience:
In my early days here in Botswana and living in a small apartment next to GSS, I got an offer of a plot (rented) in a charming village within reach of my motorbike. I made a deal with a local builder of making me two huts (roundavels), one for sleeping and one for eating + a pit latrine and water connection.
I handed out the money necessary for concrete blocks and some bags of cement. Simultaneously, a lady neighbor and mother of two small ones, started building her hut from sundried bricks she had made during a couple of months and covered her entire yard. Before my sleeping hut was up to roof height, she had moved in to her new house, neatly plastered the traditional way – of course I realized that her traditional hut needed a lot of maintenance in the rainy season but my conclusion was clear – high building standards take time and money!
Also, my firm belief was that construction problems here are often lack of supervision. Correct me if you can! And these conclusions are of importance when we talk about housing of the “common man” which is where I’m heading right now.
I’m not saying this to embarrass the “large scale” construction industry – I know since long that they know perfectly well how to handle the issue of “prefab” – often the key to successful construction of scale. Following story might be of interest:
The construction of Sowa Town and the timely needs of the mining company didn’t seem to be congruent at the planning stage. But problems were solved and this will show the prudence of my current critical mind. Skills and determination were at hand and problems were overcome quite easily due to foresight and experience of the involved specialists!
In short – there was the task of building more than 650 houses in a short time. The choice was – hand built masonry houses that would take a hoard of skilled bricklayers and supervisors (that wasn’t within the borders of Botswana) or some kind of “prefabrication and fitters” that many large construction firms could supply (in chorus). The clever architect from Anglo-American, Tony Young, recommended the “prefab” concept and a site factory. Consequently, housing needs were met with few delays.
To show you what this involved, I give you some illustrations from “Planning 113” of 1992. The prefab factory and construction worked like this:
Consequently, I see no problem in the “large projects” done by BHC, Time and a few other developers. But it always looks to me as “experiments” rather than necessity. There is seldom any follow up of it, unfortunately – we’re always starting from zero.
But coming to building materials, there is a serious oversight here. And I’m talking about modern building blocks that have been used in more industrialized countries since the late 1920’s – the so called Autoclaved Aerated Concrete (AAC), produced under different labels since the old patent lapsed. Ytong, Leca, Xella, Siporex - the list is long.
* It’s lightweight concrete of very exact dimensions easy to cut to preferred shape (by saw) and hardly in need of more than one millimeter of very thin mortar;
* Furthermore, the products have much more of interesting advantages compared to conventional concrete – it uses less concrete since Portland cement is one of the most energy and carbon-intensive building materials;
* Despite the energy-intensive autoclaving (baking) process, manufacturers say it takes about 50% less energy to make, because of the lower Portland cement content by volume and so far this no one has challenged this claim;
* It’s lighter which cuts down transportation costs and fuel use;
* It’s a better insulator to heat and cold and has excellent sound proof properties;
* It is also fire resistant.
A drawback is the fact that we have no manufacturer in Botswana but rumors are that there is someone experimenting with it somewhere in Gaborone North. It would be interesting to hear from him. Maybe he is also suffering from this modern syndrome of “patents” as most people in need of affordable medicine.
Another one is that AAC is only feasible for low and mid-rise buildings – hence very popular for single family houses, schools etc. For higher buildings, reinforcements are needed – and most manufacturers have systems and solutions for this.
AAC has the advantage that it can be produced in closed factory conditions as the “baking” gives unwanted emissions (but less than ordinary curing cement - remember the high amount of CO2 produced by this method).
However, this fault in manufacturing ordinary stones can also be “cured” and it as to do with the ballast/aggregate used. Today it is mostly crushed gravel of certain size. It is clear that things are happening today from the sites I’ve been clicking. The new thing is to swop the old kind of aggregate to pebbles or crushed AAC. Then the old type of concrete stone will keep the CO2, dissolved in the AAC elements and the large amount of carbon is neutralized inside the stone. Clever – but it will need an interested manufacturer and probably a more expensive product.
I will probably write more on this issue in the future and I’ll end with some pictures of the new/old lightweight AAC and it’s following here.
"Illustration 2"
Jan Wareus
Plain Talk –Dec 21/2012
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