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.


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


Popular Building Techniques and Material Utilisation in Low Income Tropical Housing; A case for a sustainable materials selection toolkit

This post sets to make the case for a tool that has been born out of an interrogation of the complex construct that is housing. Aspects that may contribute towards improving the quality, and, reduce the cost and impact of construction processes on the environment are of particular interest. The blog post thus, focuses on building a case for the development of a sustainable materials selection toolkit.

Buildings and their use have been noted to be a major consumer of energy and materials. It is estimated that 40% of the world’s energy is consumed by buildings, during construction and operation. It is no surprise that worldwide, there is a growing concern on the need to manage the world’s available resources better as observed by increasing literature and mobilisation on the subject of sustainability. Studies and discussions though, with regard to energy use and sustainability in the construction industry are often pre-occupied with operational energy of buildings. However, improvements in construction standards, ever improving energy efficient appliances, zero carbon energy supply on site imply that the total whole life carbon foot print is getting smaller while embodied energy and associated emissions are becoming more important in relative terms. (Lane, 2010)

This situation, it can be theorised, is true for low-income tropical housing in Uganda, since there is little or no heating and or cooling energy load because of the relatively mild climatic conditions. Furthermore, the relative poverty of low-income households implies that the prevalence of heating, ventilation and air conditioning systems (HVAC) is low. It is therefore clear that in this context, appropriate material use and selection is important in the promotion of sustainability in the construction of housing.

The case for a materials selection toolkit as a part of efforts to sustainably contribute towards the development of low-income housing is made when one considers the fact that in Uganda, low-income housing is synonymous with slums and more accurately, informal housing. Informal housing encapsulates slums, squatter settlements, marginal settlements, spontaneous settlements, transitional settlements and other settlement typologies that exist without proper planning permission and outside of the formal construction sector. This marginal existence implies that housing is seldom procured with the assistance of professional help. Rather, construction decisions are often driven by a variety of factors — some of which are baseless, to say the least. A materials selection toolkit would provide various implementers (developers, designers, artisans, building and construction managers) and receivers (clients, users, and the general community) involved in the construction of buildings with a manageable method to select building materials in a structured, measurable, and meaningful way.

The proposed tool is intended to compare materials based on the primary sustainability indicators, that is, environmental, social and economic ramifications. The indicators are detailed into criteria that include: for environmental indicator – impacts and life cycle; for the social indicator – health and safety, taste and preference, and performance of the material; and cost of the material as the criterion for the economic indicator. These criteria are further broken down into sub-criteria, which are the factors that should influence material selection. These include but are not limited to toxicity, embodied energy, fire resistance, aesthetics, cultural influences, maintenance, acoustic properties and moisture resistance.

Information on various materials’ ability to meet the exhaustive sub criteria, in their utilisation in various parts of the building is being gathered and the proposed weighing methodology being tested. The expected outcome is a series of scores, with the most sustainable material garnering the highest points. This therefore serves as an easily applicable and useful tool from which material choice can be made with little technical knowledge.


Lane, T. (2010). Embodied energy: The next big carbon challenge. Available at: <Building.co.uk/embodied-energy-the-next-big-carbon-challenge/5000487.article> Retrieved: 15. July. 2014.

UN-Habitat. (2010) Uganda urban housing sector profile. Nairobi: UN-Habitat

Popovic, J. M., Kosanovic, S. (2009). Selection of building materials based upon ecological characteristics: Priorities in function of environmental protection. SPATIUM International Review. no.20 pp. 23-27


Did German architect Ernst May invent the “Muzigo”?

Ernst May was a German architect and urban designer credited for his contribution towards easing Frankfurt’s housing shortage in the 1920’s and 30’s. So, how is it possible that one credited for fundamental work in one of the worlds greatest cities could have created the symbol of poor housing in Kampala?

Muzigo – name given to single room tennement often found in low-income settlements 

One roomed muzigo - Mbuya  Source: Nnaggenda-Musana & Vestbro (2013)
One roomed muzigo – Mbuya
Source: Nnaggenda-Musana & Vestbro (2013)

In order to understand the connection between May and the “Muzigo,” one has to consider how housing policies in Uganda have impacted stakeholders involved in housing supply. Housing policy in Uganda can be broken down into three phases, pre-colonial, colonial and post-colonial. Before colonialism, the area that currently makes up Uganda was composed of a rural based population of hunter-gatherers and farmers. With exception of the “Kibuga,” – the traditional centre of the Buganda Kingdom, there were no notable urban areas. Housing was the responsibility of individual households. The family head, often helped by neighbours in the construction process, was responsible for housing provision (Sanya in Nnaggenda-Musana & Vestbro, 2013). With the advent of colonialism in 1893, Uganda was declared a protectorate and Entebbe was declared the Capital of the new protectorate. In 1903 the Uganda ordinance was passed; this ordinance gave the Governor the powers to define the boundary of Kampala. This was followed in 1912 by Kampala’s first plan. The plan was intended to control and direct development, however it must be mentioned that it gave priority to upper and middle-class white and/or Asian populations and was therefore focused on Nakasero and old Kampala (UN-Habitat, 2007.)

The indigenous population was largely ignored with the assumption that they would be migrant in nature, commuting from their rural based abodes to work in the urban areas. In 1930 Ernst May generated the first comprehensive plan for Kampala that included settlements for middle and low-income housing for Asian and African populations (Nnaggenda-Musana & Vestbro, 2013.) These settlements were located in Nakawa and Naguru, on the outskirts of the main industrial and commercial areas. The low-income dwellings were intended to provide accommodation for male labourers who it was still assumed would remain migrant in nature.

This is supported by the fact that the spatial nature of the dwellings did not afford living spaces able to house a family. Spatially, the housing provided for a sleeping area and a kitchenette. The units were arranged around a quadrangle where other living activities could take places. Shared bathrooms and toilets were housed in a block off the enclosing units.

Low-income housing unit nakawa Source: Author
Low-income housing unit nakawa
Source: Author


Layout of low-income housing unit - Nakawa Source: Author
Layout of low-income housing unit – Nakawa
Source: Author

May’s low income housing, I theorise, gave rise to the modern day one roomed tenement commonly referred to as “Muzigo.”


UN-Habitat. (2007) Housing for all: The challenge of affordability accessibility and sustainability. Nairobi: UN-Habitat. Nnaggenda-Musana, A., Vestbro, D. U. (2013) Upgrading with densification. Global Journal of Engineering, Design and Technology. Vol.2, no.1, pp. 27-72.

Nnaggenda-Musana, A., Vestbro, D. U. (2013) Upgrading with densification. Global Journal of Engineering, Design and Technology. Vol.2, no.1, pp. 27-72.