Chilling Prospects: Sustainable cooling in buildings and cities – Nigeria case study
Nigeria is one of the Critical 9 [1] countries facing a significant cooling access gap, with 114.9 million people (53 percent of the total population) at high risk due to high temperatures. This represents a significant share of the population living in poverty and lacking access to sufficient and reliable electricity.
Policy, practical and research initiatives are underway to adapt and establish sustainable cooling in Nigeria’s buildings and cities. These efforts aim to enhance human comfort and safety while simultaneously curbing the country's excessive energy consumption and greenhouse gas (GHG) emissions.
In 2017, the first Nigeria Building Energy Efficiency Code was launched following a process of existing building code analysis, stakeholder consultation, industry training and a demonstration project that ensured it was tailored to the local context. [2] The code follows a methodology that prioritizes passive design to reduce energy demand and encourages efficient building systems to reduce energy consumption.
Passive design considers local climate conditions, building orientation, form, massing, and materials to minimize the need for mechanical and electrical systems. In hot climates, this involves providing solar shading, natural ventilation opportunities and passive cooling through thermal mass and evaporative cooling, where appropriate. Passive design, including nature-based solutions, plays a crucial role in sustainable cooling for cities and buildings, regardless of whether air-conditioning is utilized.
A simulated demonstration project highlighted how cost-effective measures such as window film and shading can reduce cooling energy demand by 20 percent compared to typical design and construction methods. With the addition of an insulated building shell, the cooling demand reduction reaches 44 percent.
The new building code mandates passive design requirements for residential and office buildings, including a maximum window-to-wall ratio of 20 percent or adequate solar shading and roof insulation with a thermal resistance of at least 1.25 m2K/W (this measures the resistence to heat flow known as the R-value).
In terms of efficiency, the code stipulates that all air-conditioning units must have a minimum Energy Efficiency Ratio (EER) of 2.8 (this is the ratio of output cooling energy to input electrical energy, i.e. a EER of 2.8 means 1kWh of electricity will provide 2.8kWh of cooling energy). This requirement is further supported by the government and the UNEP project "Scaling Up Energy-Efficient and Climate-Friendly Cooling in Nigeria’s Nationally Determined Contributions Revision", which established a National Technical Committee in March 2023. [3]
In addition to formal building sectors, paying special attention to informal settlements and socially vulnerable communities is crucial, which often experience higher heat exposure due to dense housing, heat-trapping construction materials, and limited vegetation. One study showed that 70 percent of occupants in low-income housing in Abuja experience thermal discomfort. [4] Nature-based and passive design solutions can be implemented to lower internal temperatures in low-income housing, mitigating thermal discomfort and preventing the negative health effects of heat stress. For instance:
- In Lagos, vegetation on external walls (green walls) reduced indoor temperatures by an average of 2.3°C, achieving 90-100 percent internal comfort conditions. [5]
- Shading devices, like verandas, can reduce the frequency of indoor thermal discomfort by 8.5-19.5 percent according to validated simulations. [6]
Effective implementation is crucial for the success of any energy-efficiency building code or sustainable cooling solution. In Nigeria, raising awareness and fostering collaboration among all stakeholders in the building industry is essential for implementing its Building Energy Efficiency Code [7]. Moreover, implementing passive design measures in low-income urban environments requires a comprehensive approach, including community participation, capacity building and ongoing monitoring and evaluation.
Notes and references
[1] The Critical 9 countries are: Bangladesh, Brazil, China, India, Indonesia, Mozambique, Nigeria, Pakistan and Sudan.
[2] Geissler, Susanne & Österreicher, Doris & Macharm, Ene. (2018). Transition towards Energy Efficiency: Developing the Nigerian Building Energy Efficiency Code. Sustainability. 10. 2620. 10.3390/su10082620.
[3] https://united4efficiency.org/inauguration-of-national-technical-committee-drives-progress-towards-energy-efficient-and-climate-friendly-cooling-in-nigeria/
[4] Michael U. Adaji, Timothy O. Adekunle, Richard Watkins, Gerald Adler, Indoor comfort and adaptation in low-income and middle-income residential buildings in a Nigerian city during a dry season, Building and Environment, Volume 162,2019,106276,ISSN 0360-1323, https://doi.org/10.1016/j.buildenv.2019.106276.
[5] Akinwolemiwa, O.H.; de Souza, C.B.; De Luca, L.M.; Gwilliam, J. Building community-driven vertical greening systems for people living on less than £ 1 a day: A case study in Nigeria. Build. Environ. 2018, 131, 277–287
[6] Abdulkareem, M.; Al-Maiyah, S.A.M. Environmental Performance of Abuja’s Low-Income Housing: Understanding the Current State to Inform Future Refinement. In Proceedings of the PLEA (Passive Low Energy Architecture) Conference, Hong Kong, 10–12 December 2018.
[7] Ochedi, Ekele & Taki, Professor. (2019). Towards Energy Efficient Buildings in Nigeria: Challenges and Opportunities. JOURNAL OF ENGINEERING AND ARCHITECTURE. 7. 10.15640/jea.v7n2a14.
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