©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.
1 – rammedearth.org - http://rammedearth.org/index.php?option=com_content&view=article&id=8&Itemid=9
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
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