An investigation into the environmental sustainability of buildings in South Africa with a focus on timber building systems

Crafford, Philippus Lodewicus (2019-04)

Thesis (PhDFor)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Buildings are responsible for about 33% of global anthropogenic carbon dioxide emissions, high-energy consumption and other environmental resource uses. Numerous studies over the past 20 years showed that wood-based constructions have lower environmental impacts in terms of energy use, global warming potential, air pollution, water pollution and solid waste production than steel and cement-based systems. However, there are still questions about the accuracy of green building rating tools. The objectives of this research were to (1)critically examine established international green building rating tools and methods to measureenvironmental impacts of buildings, (2)to investigate and quantify the environmental impact of selected building systems, components,and processes (including transport) relevant to the South African context, and (3)to develop a local environmental impact base and comparison models for timber-based buildingand future resource demand in South Africa. A review of green building rating tools indicated that the well documented environmental benefits of using wood was not sufficiently reflected in these rating systems. Life cycle-assessment is recognized as the best way to holistically evaluate the environmental impacts of a building. However, there is a critical need for local life cycle assessment based research in South Africa and other developing countries on building products and processes. At present, more than 70% of all sawn timber in South Africa is used in buildings, mainly in roof structures. A comparison between several roof truss systems (South African pine, Biligom and light gauge steel) using the life cycle assessment method showed that the two timber systems had overall the lowest environmental impact. Although the difference between the timber systems was small, light gauge steel had a 40% higher normalised impact over all assessed environmental impact categories. In a modelling analyses where different future building market scenarios in South Africa were compared, it was shown that if wood based residential buildings increase its market share to 20%, the embodied energy and global warming potential of the sector decrease by 4.9% from the current levels. If all new constructions is wood based, the total embodied energy and global warming potential of the residential building sector will decrease by 30.4%. It was shown that with the use of wood resources currently exported as chips, as well as planting trees in areas that have been earmarked for afforestation, it will be possible (in the long term) to sustain a future residential building market where all constructions are wood based. A decision support tool was developed to compare the environmental impact of timber transport in and to South Africa. Transport linked to local and international timber sources and markets were modelled for global warming potential and primary energy impacts. It was shown that the Johannesburg, Nelspruit and Durban markets were well located within current local truck networks and showed lower global warming potential (GWP) values per ton kilometre compared to Cape Town and Port Elizabeth markets. Results also illustrated that importing timber from regions such as Cacador, Brazil to the Cape Town and Port Elizabeth areas using container shipping will have a lower global warming potential impact than using timber from the Nelspruit area with truck transport.

AFRIKAANSE OPSOMMING: Geboue veroorsaak tot 33% van globale antropogeniese koolstofdioksiedvrylatings, hoë energie gebruik en ander omgewingshulpbron eise. Talle studies oor die afgelope 20 jaar toon dat houtgebaseerde konstruksie laer omgewingsimpakte het in terme van energiegebruik, globale verwarmingspotensiaal, lugbesoedeling, waterbesoedeling en vaste afvallewering in vergelyking met staal- en sementgebaseerde sisteme. Nogtans is daar steeds vrae oor die akkuraatheid van groenbou graderingstelsels. Die doel van die navorsing was om (1) die bestaande internasionale groenbou graderingstelsels en -metodes om die omgewingsimpak van geboue te meet, krities te ondersoek, (2) om die omgewingsimpak van sekere bousisteme, komponente en prosesse (insluitend vervoer) relevant tot Suid-Afrika te ondersoek en te kwantifiseer en (3) om ‘n plaaslike omgewingsimpak basis en vergelykingsmodelle vir houtgebaseerde geboue en toekomstige hulpbronvraag in Suid-Afrika te ontwikkel. ‘n Analise van groenbou graderingstelsels toon dat die omgewingsvoordele van houtgebruik nie goed gedokumenteer is nie en ook nie voldoende in die graderingstelsels aangetref word nie. Lewensiklus-analise word erken as die beste manier om die omgewingsimpak van geboue holisties te evalueer. Nogtans is daar ‘n kritiese behoefte aan plaaslike lewensiklus-analise gebaseerde navorsing in Suid Afrika en ander ontwikkelende lande oor bouprodukte en -prosesse. Tans word meer as 70% van alle saaghout in Suid-Afrka gebruik in geboue, hoofsaaklik in dakstrukture. ‘n Vergelyking tussen verskillende dakkapsisteme (Suid Afrikaanse denne, Biligom en ligte staal) met behulp van lewensiklus-analise metodiek, het getoon dat die twee houtsisteme ‘n algehele laer omgewingsimpak het. Alhoewel die verskil tussen die onderskeie houtsisteme klein was, het die ligte staal ‘n 40% hoër as genormaliseerde impak getoon. In ‘n modelleringsanalise waar verskillende toekomstige scenarios van die boumark in Suid-Afrika vergelyk word, toon dit dat as houtgebaseerde residensiële geboue se markaandeel toeneem tot 20%, die opgesluite energie en globale verwarmingspotensiaal van die sektor daal met 4.9% teenoor die huidige vlakke. As alle nuwe konstruksie houtgebaseer is, sal die opgesluite energie en globale verwarmingspotensiaal van die sektor met tot 30.4% daal. Verder is daar getoon dat genoegsame hulpbronne beskikbaar sal wees om ‘n slegs hout residensiële mark volhoubaar te ondersteun oor die kort- en langtermyn. Dit sal vereis dat huidige houtspaanders, wat tans uitgevoer word, plaaslik gebruik word en bome aangeplant word op die voorgestelde areas. ‘n Besluitnemingsmodel is ontwikkel om die omgewingsimpak van die vervoer van hout in en na Suid-Afrika te vergelyk. Vervoer na plaaslike en internasionale houtbronne en -markte is gemodelleer om opgesluite energie en globale verwarmingspotensiaal te ondersoek. Daar is bevind dat die Johannesburg, Nelspruit en Durban markte goed geleë is ten opsigte van die huidige padvervoer netwerke, en het laer opgesluite energie en globale verwarmingspotensiaal getoon as Kaapstad en Port Elizabeth markte. Die bevindinge toon ook dat om hout in te voer van Cacador, Brasilië na Kaapstad en Port Elizabeth areas deur middel van skeepsvervoer, laer opgesluite energie en globale verwarmingspotensiaal toon, in vergelyking daarmee om hout vanaf die Nelspruit area per vragmotor te vervoer.

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