The CSIR Köppen-Geiger map for South Africa on a very fine 1 km x 1 km grid. The map is based on 1985 to 2005 Agricultural Research Council data.
A quantitative hand-drawn world map of climate classification published by Wladimir Köppen in 1931. This Köppen classification distinguishes between equatorial, arid, warm temperate, snow and polar climates – three equatorial, four arid, nine warm temperate, 12 snow and two polar climates, thus a total of 30 climates.
Contributing to the design of buildings that are responsive to the specific characteristics of the climate in which they are placed, the CSIR has created a new Köppen-Geiger map to quantify the climatic conditions in South Africa with unique accuracy.
The CSIR is committed to promoting sustainability in the built environment and thus pursues building design that is climate-responsive. The responsiveness of buildings to their specific climate zones is key, regardless of the solutions and technologies employed in the design and engineering of building.
Thermal solutions could include passive design technologies (such as solar heating, thermal mass, natural ventilation or direct and indirect evaporative cooling), mechanically engineered solutions (e.g. air conditioning) or hybrid strategies. These lead to improved building performance, enhanced energy efficiency and optimised internal environmental conditions.
South Africa has 13 primary climate categories, according to a detailed, new map developed by the CSIR to quantify the climate in South Africa with unique accuracy. Worldwide, there are a total of 30 climate classifications – South Africa’s main climate zone include one that is equatorial, four that are arid and eight warm temperate zones.
The research in this area is undertaken by the CSIR’s Dr Dirk Conradie and Tichaona Kumirai, with technical support by Sheldon Bole. Their findings were presented at an international conference, ‘Smart and Sustainable Built Environments’ in June in Sao Paulo, Brazil. The title of their paper is The creation of a South African climate map for the quantification of appropriate passive design responses.
The new CSIR map followed a close look by researchers at the climate map in SANS 204-2 (2008), which is currently used by South African built environment professionals in design decision-making. The CSIR considered whether the resolution of the climate information was adequate to support optimal design in an emerging era of green building practice. Researchers also looked at the likely effect of climate profile change on building performance over a 100-year horizon.
The first quantitative hand-drawn map of climate classification was published by Wladimir Köppen in 1900. A trained plant physiologist, he realised that plants were indicators for many climatic elements. He classified five vegetation groups that distinguished between plants of the equatorial zone, the arid zone, the warm temperate zone, the snow zone, and the polar zone.
In 1961, Rudolf Geiger produced an updated version of the Köppen classification, with Austrian researchers creating a contemporary version in 2005.
Using 20 years of precipitation and temperature data, CSIR researchers developed a Köppen-Geiger climatic classification, which is a significant refinement of the six-zone model of SANS 204-2.
Simulations of building performance in SA
In building design, insulation and thermal mass are the two key factors for determining the comfort levels, especially when natural ventilation is used. The effective combination of these differs significantly between climate zones, for example, between Cape Town, Pretoria or Durban.
The CSIR team modelled building performance for a typical masonry building and a recently introduced light-weight steel frame building within selected climate zones in South Africa. From this a clear pattern emerged as to the most appropriate passive construction response within a particular climate zone.
Simulations were used to evaluate and compare the performance of the masonry and light-steel frame houses regarding energy consumption for space heating and cooling. Six Köppen regions were used to relate actual building performance to climate region, with weather files utilised for Pretoria, Bloemfontein, Cape Town, Durban, Musina and Kimberley.
Some new material composites were introduced in the materials database to represent typical building materials used in the construction of heavy and light-weight buildings in South Africa. CSIR researchers also calculated the thermal characteristics.
Advanced computational building performance software products make it easier to qualify and quantify the effect of a particular building design before construction. This assumes that sufficient weather files are available to support the process. In reality, weather data suitable for predictive building performance simulation for South Africa are incomplete.
The adoption of the South African Köppen-Geiger map would allow building designers to rapidly identify appropriate climate-responsive design techniques and would facilitate the computational performance modelling of buildings. This would be achieved by applying synthesised approximations of weather data where data are not available.
Change in climate demand changed building design
All indications are that South Africa can expect a significant change in climate. Such a change will have a profound impact on the built environment and on how buildings of today will perform in the future. From past data, it is clear that some climate changes have already been experienced in southern Africa.
An example is Mapungubwe, located in the Shashe-Limpopo river basin. This region had an adequate rainfall during the Medieval Warm Epoch, usually dated from about AD 900 to 1300. The current rainfall average of 320 to 350 mm per year is not sufficient for traditional subsistence agriculture. Today, that area is an extremely arid region, with semi-desert qualities.
Another example is the eastern parts of South Africa, especially the coastal regions that are predicted by means of sophisticated general circulation models to become wetter. Indications are that the equatorial area currently ending at Richards Bay will extend down to East London in the next 100 years.
It is clear to the CSIR research team that, if climate change is expressed in terms of Köppen category changes, it is feasible to predict future building performance characteristics within that particular location and craft buildings with these parameters in mind.
Dr Dirk Conradie