Quantifying the sustainability of the built environment : the development of a complete environmental life cycle assessment tool

Van Noordwyk, Arina (2015-03)

Thesis (MEng)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: Sustainability is becoming an increasingly important aspect in all facets of engineering. It is in particular an important consideration in the structural engineering industry, due to the prominence of the negative impact this industry has on the environment, both on a national and international scale. The problem, however, is that sustainability is a mostly unknown and highly debated topic. It is not only difficult to quantify, but even difficult just to define. In the field of structural engineering it is an especially difficult task to consider sustainability. It is still a very new field of research and difficult to apply. It is therefore important that continued research be done in order for there to be a better understanding of how sustainability should be considered and applied in the context of structures. In an attempt to assess the environmental impact of building structures, there are two basic approaches that are followed. The first, the application-oriented method, is a simple, points-based system. The second, the analysis-oriented method, makes use of detailed indices and factors to quantify the impact. This study aims to develop an analysis-oriented method, specifically designed for the complete life cycle of buildings in the South African environment. This is accomplished by continuing the work that was started by Brewis (2011), and continued by Brits (2012). Brewis developed the approach for the pre-use phase, while Brits developed the approach for the end-of-life phase. Both focussed their application on low-cost housing development. However, the approach is defined for the use of the analysis of a building envelope. The details of developing the environmental life cycle assessment (LCA), as well as the approaches for the pre-use phase and the end-of life phase are discussed in Chapter 3. The study develops the use phase of the proposed environmental life cycle assessment for buildings in Chapter 4. It discusses in detail the two main components of the use phase, namely maintenance and operation. While maintenance is concerned with the replacement of building materials in the structure, the operation component is concerned with the energy needs during the use phase. It is determined that the energy use that is directly related to the building envelope is the energy required for the space heating and cooling of the building. This is due to the fact that the thermal properties of the building envelope influence the thermal environment within the building, and thereby impact the use of energy to regulate that thermal environment. In order to make the most use of both of these components within the application of the proposed LCA, it was decided to model a residential building structure that uses consistent energy to regulate the thermal environment within the structure. However, it is not only the objective to use the proposed LCA as an assessment tool, but also as a comparative and optimisation tool. Therefore one component, the external walls, was selected as a variable component. This component was varied to form a total of nine different buildings. These nine buildings were then used in a comparative study in order to try to determine an optimum choice of external walling system, based on the results of the environmental impacts determined in the LCA. It is also used to try to explain exactly how and to what extent the external walling system contributes to the environmental impact, and what useful application value we can gain from this knowledge. The results showed that a minor increase in the materials impact (due to attempts to improve the thermal capacity of the external walls) were in most cases countered by a decrease in the energy impact, which in seven of the eight alternative external walling systems led to a net decrease in environmental impact (EI) categories one to four. It was also found that with the increase of the R-value of the external walling systems, the environmental impact of the building steadily decreased, in terms of four of the five impact categories. The only exception to these trends was found in the fifth impact category: waste generation. The reason for this is the fact that energy impact in this environmental impact category is negligible, and therefore does not contribute much to the net change in environmental impact.

AFRIKAANSE OPSOMMING: Die belangrikheid van volhoubaarheid neem al hoe meer toe in alle aspekte van ingenieurswese. In die industrie van struktuuringenieurswese is dit van besonderse belang as gevolg van die prominente negatiewe impak van hierdie industrie op die omgewing, op beide ’n nasionale en internasionale skaal. Die probleem is egter dat volhoubaarheid nog meestal gesien word as ʼn onderwerp wat onbekend en hoogs debatteerbaar is. Dit is nie net moeilik om te kwantifiseer nie, maar selfs moeilik om dit net te definieer. In struktuuringenieurswese is dit veral ʼn moeilike taak om volhoubaarheid in ag te neem. Dit is nog ʼn baie jong studieveld wat moeilik is om toe te pas. Dit is dus van uiterse belang dat verdere navorsing gedoen word sodat daar ʼn beter begrip kan wees van hoe volhoubaarheid op die lewensiklus van strukture toegepas kan word. In 'n poging om die omgewingsimpak van die geboustrukture te evalueer, is daar twee basiese benaderings wat gevolg kan word. Die eerste, die toepassingsgeoriënteerde metode, is 'n eenvoudige, punte-gebaseerde stelsel. Die tweede, die analise-georiënteerde metode maak gebruik van gedetailleerde indekse en faktore om die omgewingsimpak te kwantifiseer. Hierdie studie beoog om 'n analise-georiënteerde metode te ontwikkel, wat spesifiek ontwerp is vir die analise van die volledige lewensiklus van geboue in die Suid-Afrikaanse omgewing. Dit word gedoen deur die voortsetting van die werk wat begin is deur Brewis (2011), en voortgesit is deur Brits (2012). Brewis het die benadering vir die eerste fase (voor-gebruik) ontwikkel, terwyl Brits die benadering vir die finale fase (einde-van-lewe) ontwikkel het. Beide het die fokus van hul toepassings geplaas op lae-koste behuising. Die benaderings is egter gedefinieer vir die algemene analise van ʼn gebou se raamwerk. Die besonderhede van die ontwikkeling van die omgewingslewensiklus analise (OLA), asook die benaderings vir die eerste en finale fases, word in Hoofstuk 3 bespreek. Die studie ontwikkel die gebruiksfase van die voorgestelde omgewingslewensiklus analise vir geboue in Hoofstuk 4. Dit bespreek die twee hoofkomponente van die gebruiksfase, naamlik die instandhouding en bedryf. Terwyl instandhouding gemoeid is met die vervanging van boumateriale in die struktuur, is die bedryfskomponent gemoeid met die energie behoeftes tydens die gebruiksfase. Dit word bepaal dat die energie verbruik wat ʼn direkte verband het met die gebou se raamwerk, die energie is wat nodig is vir die verhitting en verkoeling van die gebou. Dit is te danke aan die feit dat die termiese eienskappe van die gebou se raamwerk die termiese omgewing binne die gebou beïnvloed, en sodoende 'n impak het op die energie wat benodig word om die temperatuur te reguleer. In ʼn poging om die spektrum van die voorgestelde OLA ten volle te benut, is dit besluit om die toepassing daarvan te illustreer op 'n residensiële gebou wat van konsekwente energieverbruik gebruik maak om die termiese omgewing binne die gebou te reguleer. Dit is egter nie net die doel om die voorgestelde OLA te gebruik as 'n assesseringsinstrument nie, maar ook om die OLA se funksie as ’n vergelykende en optimaliseringshulpmiddel te illustreer. Dus is een komponent, die eksterne mure, gekies as 'n veranderlike komponent. Hierdie komponent is gewissel om 'n totaal van nege verskillende geboue te vorm. Hierdie nege geboue is gebruik in 'n vergelykende studie in 'n poging om 'n optimale keuse van eksterne mure te bepaal, gebaseer op die resultate van die omgewingsimpak wat in die OLA te bepaal is. Dit word ook gebruik om te probeer om te verduidelik presies hoe en tot watter mate die eksterne mure bydra by tot die omgewingsimpak, en watter nuttige toepassingswaarde geput kan word uit hierdie kennis. Die resultate het getoon dat 'n toename in die materiaal impak (weens pogings om die termiese kapasiteit van die eksterne mure te verbeter) in die meeste gevalle teengewerk is deur 'n afname in die energie impak. In sewe van die agt alternatiewe eksterne muurstelsels het dit gelei tot 'n netto afname in omgewingsimpak vir kategorieë een tot vier. Dit is ook gevind dat die omgewingsimpak van die gebou stelselmatig gedaal het met die toename van die Rwaarde van die eksterne muurstelsels, ook in terme van kategorieë een tot vier. Die enigste uitsondering op hierdie tendense is gevind in die vyfde impak kategorie: die afval wat gegenereer word. Die feit dat die effek van energie verbruik gering is in hierdie omgewingsimpak kategorie, lei tot die feit dat dit nie veel bydra tot die netto verandering in die omgewingsimpak nie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96923
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