Embodied energy and embodied carbon – the tip of the iceberg

The ELITH project stepped away from the desk and ventured into the “real” world – as many research projects do, to gather data on housing types, popular building materials, and construction techniques.

As part of a pilot study; analysis of a 50sq.m four roomed house – determined as the predominant housing typology in the peri-urban and rural setting of Nkozi Sub County, Mpigi District – revealed walling, floor finishes and roofing as major energy consumers. Walling (burnt clay brick with cement sand mortar joints and in some cases plaster as render) had 45,569 MJ; floor finishes (ceramic tiles on cement screed) had 13,843 MJ and roofing (Steel sheet on timber supports) had 10,685 MJ. Walling emerges as an outstanding energy hot spot due to its extensive area and is therefore the most logical area to begin our investigations geared towards reducing the embodied energy of low-income housing.

It was determined that burnt clay brick is a common building material that is considered readily available, durable and relatively cheap. A review of the brick production process reveals that the traditional method for burning bricks in Uganda consists of stacking a large amount of dried bricks (up to 20,000) into a large pile with a tunnel opening at the bottom into which large quantities of firewood are introduced and burnt over a period of 24-hours. The pile is plastered with mud in order to reduce heat leakage. The described process results in unevenly baked bricks and 20% waste as the bricks closest to the heat source are over burned while those farther away are under-fired (Perez-pena, 2009.) Further more, locally produced burnt clay brick is often uneven, leading to thick mortar joints during construction and often, plastering of walls to achieve a finished look. These defects lead to an increased amount of cement use in mortar and plaster that contributes to increased embodied energy of walling, recall 45,569 MJ.

However, what is 45,569 MJ as identified for walling in real or relative terms?  How is this energy obtained, what are the impacts? Burning wood fuels brick production in Uganda, immediately raising concerns on the amount of carbon dioxide produced – this is the gas often cited in global warming and sustainability literature.  However, it must be noted that wood fuel is considered carbon neutral due to the carbon sequestered during tree growth. There are other impacts: deforestation and associated out-turns – to produce the 45,569 MJ, it is estimated that the equivalent of 4 fully grown mango trees were cut down; burning wood produces many gases that include nitrogen monoxide – although in small amounts, the gas is 300 times more potent as a green house gas than carbon dioxide, methane – 21 times more potent, and carbon monoxide; and, the respiratory health impacts levied on society due to smoke production.

In sight of these challenges, we question now, do we have a better alternative, how can we improve existing technologies, and what is the rate of uptake of new technology?  Well, there is a lot that could be fronted as possible alternatives, for now a list would include: improving aspects of traditional brick, and brick making technology to produce a higher quality brick with lower embodied energy; research on alternative masonry construction techniques that include: rammed earth, stabilised soil block technology; additives for improved longevity of wattle and daub; and the most suitable way of propagating these technologies.

Reference

PEREZ-PENA, A. 2009. Interlocking Stabilised Soil Blocks; Appropriate earth Technologies in Uganda, UN-HABITAT.

So, we set forth again to find out more; join us as we develop a guide on weighted alternatives that will protect our environment, earn you a saving and improve health and well-being in our built environments

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