Architects and Climate Change Adaptation and Mitigation
Llewellyn van Wyk
Principal Researcher, CSIR
Thursday, 14 September 2017
Introduction and Background
Climate change is projected to impact drastically in southern African during the 21st century under low mitigation futures.1 African temperatures are projected to rise rapidly, at 1.5 to 2 times the global rate of temperature increase.2 Moreover, the southern African region is projected to become generally drier under enhanced anthropogenic forcing.3 These changes will have a range of potential impacts on the South African environment and economy, including impacts on energy demand (in terms of achieving human comfort within buildings and factories), water security (through reduced rainfall and enhanced evapotranspiration) and agriculture (in terms of changes in crop yield).4
Climate change impacts will however not only manifest through changes in average temperature and rainfall patterns, but also through changes in the attributes of extreme weather events. For the southern African region, generally drier conditions and the more frequent occurrence of dry spells are plausible over most of the interior.5 Tropical cyclone tracks are projected to shift northward, bringing more flood events to northern Mozambique and fewer to the Limpopo province in South Africa.6 Cut-off low related flood events are also projected to occur less frequently over South Africa in response to a poleward displacement of the westerly wind regime.7 Intense thunderstorms are plausible to occur more frequently over South Africa in a generally warmer climate.8
On the basis of the above projections, architects should take the following steps.
Land Use and Ecology
Analyze the risks associated with the particular site and if at all possible, avoid development in the following areas:
- Steep slopes may be subject to slip
- Clay soils will be subject to extensive heave and shrinkage
- Coastal properties will be subject to sea level rise and/or sea surge
- Flood plains will change, i.e., 1:100-year occurrence could become a 1:50 occurrence, and 1:50 a 1:20, and so on. Floor heights above natural ground level should be adjusted accordingly.
- Sites adjacent to open veld will be subject to more intense and frequent veld fires.
- Wind speeds are likely to increase so additional precautions are required in areas with existing high wind speeds.
Ecological value of the site
Climate change influences local biodiversity: as climate changes plant species migrate in response. The anticipated pattern is for specie to generally migrate in a south easterly direction except for the eastern coast where the anticipated migration is in a south westerly direction. Look in these directions to establish what plant species to cultivate on the site.
Establish an ecological baseline of the site and use the development to enhance the value.
Avoid introducing species that are not indigenous to that area, even if they are indigenous to South Africa. Remove existing species that are not indigenous to the location.
Protect and retain all features of ecological value, particularly where these features are connected to a larger ecological system or designated system including forest, wetland, water courses, grassland, or any other habitats considered to have ecological value.
Minimise disruption to the site in all forms but specifically bulk excavations, cut-and-fill, and terracing. Restrict the construction area of the site to a minimum, and protect those areas that fall outside of the construction area.
Take steps to reduce the impact of future extreme events on the site particularly flooding, sea surge and fire. For example, avoid concentrated stormwater discharge points that typically results from downpipes and stormwater channels. A range of Sustainable Urban Drainage System (SuDS) components are available to deal with different conditions.
Plant as many trees on the site as is appropriate to the location: this will stabilize the soil, provide shade and shelter to the building, and reduce the heat island effect.
Use permeable pavement throughout to reduce runoff characteristics and to allow ground infiltration of rainwater.
Building envelopes will need to be responsive to higher temperatures: these responses should be based on passive approaches rather than active (mechanically supported) approaches.
Roof insulation values should be appropriate to the future forecast temperatures of the location. Since the majority of radiation in South Africa is vertical, the roof design forms the most effective barrier to thermal gains. Avoid roof glazing: where this is not possible, roof glazing should be capable of being completely closed off from heat transfer.
Heat reflecting surfaces should be introduced on all horizontal surfaces to reduce heat transfer and the heat island effect.
Adjustable ventilated attics are an effective way of dealing with higher temperatures.
All external wall openings should be protected. Over and above shading, adjustable shutters that increase the thermal resistance of external wall openings should be used.
The thermal resistance of walls should be appropriate to the future forecast temperatures of the location.
Ventilation rates should be increased beyond the minimum requirements of the NBR. The appropriate level of ventilation will be determined by the future forecast temperatures for the location. Displacement ventilation should be used to increase air exchange rates. Take particular note of prevailing wind conditions to ‘drive’ displacement ventilation.
Services should be positioned in accordance with risk analysis for the location. In areas of flooding, services should be elevated wherever possible. In areas of fire risk or high wind velocities services should be buried.
Target a zero dependent building, i.e., net zero water, energy, waste, sanitation, and ecological loss. For services this will require significant reductions in demand (improved efficiencies through higher performance specifications) in order to meet off-grid supply capabilities.
Water resources are and will continue to become increasingly scarce. Use water efficient fittings throughout the development. Design to use renewable water (rainwater, stormwater, greywater, blackwater, and condensate water). Preferably design a twin-pipe system where rainwater, stormwater and greywater can be recycled. A number of SuDS components can be used to facilitate this on site. In addition, there are a number of technologies that support closed-loop water and sanitation systems: the use of these technologies is encouraged.
In line with the requirements listed in site ecology, planting that requires regular watering, such as lawns, should be avoided.
Materials will be exposed to harsher environmental conditions including solar radiation. Subject all material choices to a life cycle assessment relevant to the future climate projections for the location.
Appropriate material choices are required in areas of high fire risk, bearing in mind that veld fire events will be both more frequent and intense.
Architects have a significant role to play in adapting the built environment to climate change impacts. Lessons from Houston and Florida floods have confirmed that the built environment is more resilient where strategic interventions have been put in place.
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3 Christensen, J., Hewitson, B., Busuioc, A., Chen, A., Gao, X., Held, I., Jones, R., Kolli, R., Kwon, W-T., Laprise, R., Magana Rueda, V., Mearns, L., Menendez, C., Raisanen J, Rinke A, Sarr A, Whetton P (2007). Regional climate projections. In: Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt, AB, Tignor M, Miller HL (eds). Climate change 2007: the physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Inter-governmental Panel on Climate Change. Cambridge: Cambridge University Press; Niang et al, 2014; James and Washington 2013; Engelbrecht et al, 2015)
4 Engelbrecht et al, 2015.
5 Christensen et al 2007; Engelbrecht, F., McGregor, J. and Engelbrecht, C. 2009. “Dynamics of the conformal-cubic atmospheric model projected climate-change signal over southern Africa.” Int J Climatol 29 1013-1033.
6 Malherbe, J., Engelbrecht, F. and Landman, W. 2013. “Projected changes in tropical cyclone climatology and landfall in the Southwest Indian Ocean region under enhanced anthropogenic forcing.” Clim Dyn 40 2867-2886.
7 Engelbrecht 2013