Showing posts with label thermal comfort. Show all posts
Showing posts with label thermal comfort. Show all posts

27/06/2011

Earthen buildings today...

A few weeks ago I have received a link to Patricio Arias new website, which made me think about what it meant to build with earth today.

Patricio Arias is an architect from Chile who is definitely amongst the group of very talented people – such as Rick Joy, Plano B, Martin Rauch, Marcelo Cortes (with whom he has worked) – looking at the current use of earthen materials as a product of our time and, therefore, bringing earth as a building material to the mainstream of the building industry.

Although I still struggle a bit with the concept of ‘contemporary earthen architecture’ (I shall leave this issue to a later post), I have to say that I have seen quite a lot of examples of buildings that would qualify as such. However, Patricio’s approach differs substantially from all of what is already out there.
I met Patricio in a conference last year and have been following his work ever since. I was able to witness his enormous passion for architecture in general and, in particular, for the way earth can be used to meet current needs and demands. Patricio Arias’ work reveals a deep understanding of both architectural space and the essence of building materials. Moreover, he makes a clear statement with his buildings by proclaiming to the world that it is possible to create extraordinary architecture with earth, using one or several of its many associated construction techniques. His architecture emerges from within its time and context, and reveals that, no matter what the future brings in terms of fashion or architectural styles, the same approach can be pursued and successfully accomplished.
As always, some criticism has also been made about the use of the main technique used by Patricio – tecnobarro (or quincha metalica). This was mostly to do with the introduction of steel as a structure for the earthen walls. Those who are more “purists” in what concerns the use of earth as building material often question the compatibility of earth with concrete or steel. In a way I can understand this concern, especially since there are complex chemical processes involved in the heat and humidity transfer of unbaked earthen materials. This is the reason why, for example, one usually combines natural insulating materials (such as cork or sheep wool) with earthen building elements. Nevertheless, I am not aware of any studies that have been carried out in order to test this theory. I had this same conversation with Patricio, who was very interested in finding out whether the thermal performance of the buildings he designs is in any way influenced by the use of steel.

In addition to the thermal performance, I would probably add a very current issue – the ecological footprint and environmental impact of quincha buildings. Apparently, the overall sustainability of these buildings may be somewhat compromised, due to the energy intensive overall construction process (when compared to traditional earthen building techniques). Not only some of the materials have a high embodied energy, but also mechanical methods are used throughout.

Again, I am certainly not an expert in this type of earthen technology, nor can I refer to any study that has been carried out to share some light on this particular subject; however, one has to wonder about the viability of applying this technique to other, perhaps not so resourceful, contexts.

While some features may be questioned, others are without a doubt, very positive. This consists of a very effective seismic resistant construction. Once more, I refer to what Patricio stated himself after the last major earthquake in Chile: his houses were not affected, whereas others have literally crumbled apart.

In my opinion, we do not always have to have a definite answer or solution for every problem encountered, there is no such thing as a universal thruth... Patricio’s buildings are incredibly interesting and appealing as architectural objects. One cannot help but feeling fascinated by them. Further to this, they bear witness to the immense possibilities and flexibility of this building material and probably are providing a view into what the future of earthen materials will be.

The main question raised here, which can easily be applied to a more general architectural universe, is whether or not the future of earthen buildings will still be one of sustainability above all? By employing mechanical processes, are we contributing towards the increase of CO2 emissions? Will that also mean that earthen buildings will not be as low-cost as they are known for? Who will be able to afford these high-quality earthen houses?

On the other hand, I can also envisage a myriad of positive aspects arising from the combination of modern technologies with such an ancient building material. One only has to look at the photos below to understand that the preconceived ideas that usually associate earth with backwardness and poorness are indeed obsolete. And this, my fellow readers, the social perception, has been the paramount obstacle against the use of earthen materials today.

For this reason, and just to conclude for today, it is my belief that if it takes a bit of a compromise in order for people to accept once and for all that “earthen architecture” is just Architecture, then I am not against some kind of hybrid approach, where one can make use of the good natural features of earth and today’s technological advances in the field of architecture and engineering.

See you soon!




Some examples of buildings designed by Patricio Arias. All images have been sourced from his website http://www.patricioarias.cl/Index.php/

01/01/2011

Earthen buildings and extreme cold

©Célia Macedo, 2010
 





The last couple of weeks have been extremely cold here in the UK.  Because of this, I found myself wondering whether earth is an appropriate material to be used in places where extreme cold weather is felt throughout the year, or at least for a long period of the year. There is some information about this out there, but not quite that much, in fact, I do not recall coming across this issue very often.

There is the general idea that earthen buildings are only appropriate to hot climates, however, some examples from unlikely places seem to prove that earthen construction can also successfully resist freezing weather conditions. This seems to be the case in Canada, where the oldest rammed building is a church that dates back to around 1842, which, despite the subzero temperatures and snow, is still standing and doing fine today [1]. Dr Paul Jaquin, who holds a PhD in analysis of historic rammed earth structures, also reminds us that it is common to find earthen buildings in the Himalayas. Jaquin thus advocates that earthen walls can resist snow during the winter months [2].

What if we are looking at modern comfort standards? Of course it is very important to know that earthen buildings can resist snow and cold structurally, but what about thermal comfort inside these earthen buildings when it is freezing cold outside? 

The solution for this may simply lie on the use of insulation, preferably applied externally. According to David Easton’s ‘The rammed earth house’, it may be necessary to consider insulation, as ‘extremely cold or oppressively hot outside temperatures can cause uninsulated thermal mass to change the direct flow of heat too rapidly’ [3]. Moreover, Stuart Fix and Russell Richman, following a technical study on the viability of earth building construction in cold climates (south and central Alberta, Canada) concluded that, provided earthen walls are externally insulated, they ‘exhibit optimal thermal mass performance, completely mitigate spalling damage, and provide great control over moisture transportation through inward drying.’ [4].

Insulation applied from the exterior of earthen walls seems to be indeed the most frequently mentioned solution to cope with very cold temperatures. Surprisingly, this is also beginning to be suggested for hot climates... Some earthen construction advocates hence suggest that only some of the walls should be insulated, rather than the whole house. So for example, in a cold climate the north and east would be insulated, while insulating a wall facing west would bring advantages in a hot climate [5].
However, this means covering the earth wall itself, which for many is the main feature of the material and should therefore remain exposed. To avoid this, there are some companies insulating rammed earth walls, not from the exterior, but from in between two layers of rammed earth walls. I guess this is somewhat similar to common double layered construction, but with rammed earth instead of brick and block.  Thanks to this internal layer of insulation, the aesthetics of the earthen wall can still be appreciated, while the temperature inside remains comfortable. Or so it is said, I have never experienced this.

I can imagine all sorts of potential problems associated with the use of insulation on earthen walls. Given the complexity of this building material, which is unlike any other, the selection of the appropriate insulation is absolutely fundamental. A wrong choice of insulation will interfere with the processes of moisture transfer and with the breathing capacity of the earth wall, which as a consequence will compromise the overall performance of the material earth.
Nonetheless, it is a fact that if we advovate that earth is one of the materials of the future, we should be definitely looking at ways of combining earth and insulation to enhance the already acknowledged natural potential of earthen materials.




3 - EASTON, D. (2007). The rammed earth house. White River Junction, Vt, Chelsea Green


5- http://lists.ibiblio.org/pipermail/homestead/2005-February/003990.html