Retrofitting South Africa's cities with green roofs: cost benefit analyses for large scale green roof implementation.

Thesis (MEng)--Stellenbosch University, 2018.ENGLISH ABSTRACT: Cities are most at risk to climate change and South African cities are no exception. To a large extent, cities are also the cause of their own demise in terms of environmental concerns and need to adapt to become more resilient. Retrofitting existing buildings with green roofs may be a key step in reducing and/or mitigating some of the environmental concerns common within urban centres. Research proposed in this thesis considers the feasibility of retrofitting existing buildings with green roofs given the current state of the green roofing industry in South African cities, specifically Johannesburg. Policies and incentives available to encourage the green roof industry and the implementation of green roofs were researched and identified. Costs and benefits associated with retrofitting the typical building situated in Johannesburg CBD were investigated. Retrofitting buildings with green roofs comes at a premium cost in countries where the green roof industry is not established. A Cost Benefit Analysis (CBA) for retrofitting an existing building with a green roof without the help of policies or incentives was compared to the “do nothing” approach. This comparison showed retrofitting is not feasible under these conditions, as the building owner will never be able to make up the additional expenses. The same comparison was made assuming different conditions, such as incentives and additional benefits. Results showed retrofitting a building becomes feasible given the following conditions: (1) the green roof can reduce the building’s energy consumption by 3%, (2) the municipality offers to subsidise 80% of the green roof installation costs and (3) reduce property tax by 2% during the green roof’s lifetime. Given these conditions a building owner will have a payback period of 7 years. Motivations for why the City would consider offering such incentives are as follows: (1) air pollution in an area of implementation will reduce given that the green roofs can increase the green fraction in the area by at least 18%. (2) The reduction in air pollution will reduce the health costs especially those related to air pollution, these savings will be equivalent to an additional 5% in property tax received from all the buildings in the area of implementation. (3) The Government of South Africa aims to reduce greenhouse gas emissions with 34% by 2020 with the implementation of carbon tax. Carbon tax has not yet been implemented: the implementation thereof is receiving much criticism and there are currently no other plans to reduce emissions. Thus, the proposed incentives can be used to reduce air pollution and offer savings to both the City and the building owners in the area where the incentives are implemented. However, the city will need 15 years to pay off these incentives.AFRIKAANSE OPSOMMING: Klimaatsverandering is ‘n groot risiko vir stede, en stede in Suid-Afrika word nie hiervan uitgesonder nie. Bestaande stede is meestal die oorwegende rede van die ondergang van hulle eie omgewing. Stede moet aanpas en meer omgewingsvriendelik word om toekomstige omgewingsprobleme te verminder en te voorkom. Groen dakke is ‘n groen tegnologie wat die potensiaal het om ‘n groot rol te speel in die omskepping van bestaande stede in meer omgewingsvriendelike areas. Navorsing wat in hierdie verhandeling voorgestel word kyk na die lewensvatbaarheid daarvan om bestaande gebou se dakke met groen dakke te vervang. Geboue spesifiek in Johannesburg se middestad was beskou in die lig van die huidige tekort aan ‘n groen dak industrie. Die moontlikheid om gebruik te maak van aansporings en beleide wat die groen dak industrie van Suid-Afrika kan aanmoedig en bevoordeel was ondersoek, asook kostes en voordele verbonde aan die gebruik van groendakke. Sonder ‘n groen dak industrie is die aanvanklike kostes van ‘n groen dak teen ‘n premie, wat beteken die gebruik daarvan is nie ekonomies regverdigbaar nie. Die lewensvatbaarheid van die gebruik van groen dakke was met ‘n koste en voordele analise bepaal. Die analise is vergelyk met die opsie om niks te doen nie, en was onderhewe aan die feit dat daar huidiglik geen aansporings of beleide vir die gebruik van groen dakke is nie. Die resultate het getoon dat groen dakke nie ekonomies regverdigbaar is indien daar nie addisionele voordele en aansporings in ag geneem word nie. ‘n Koste en voordele analise waar moontlike voordele en aansporings in ag geneem is het gewys dat ‘n groen dak ekonomies haalbaar sal wees indien: (1) die elektrisiteitsverbruik van die gebou verminder met 3%, (2) die aanvanklike koste van die groen dak verminder word met 80% as gevolg van ‘n aansporing van die stad, en (3) die gebou se erf belasting verminder word met 2% oor die lengte van die groen dak se leeftyd, ook ‘n aansporing van die stad. Hierdie aansporings en die voordeel sal die terugbetalingsperiode van die dak 7 jaar maak. Redes waarom die stad aansporings sal gee is omdat dit voordeling is vir die stad. Groen dakke kan die lugbesoedeling verminder, wat die jaarlikse koste van gesondheid kan verminder. Die stad sal jaarliks spaar in gesondheidskostes, en die lewenskwaliteit van die mense in die stad sal verbeter