Global Sustainability and the New Zealand House

Abstract

"How do you build a sustainable house in New Zealand? - is it even possible?" This thesis is structured in three parts to answer this question. The first part asks, then answers, "What is sustainability?", "How do you measure sustainability?" and "How do you know when you have reached sustainability - what is its limit?" The second part describes the methodologies for conducting embodied energy and CO2 analysis. The third part applies the results of the sustainability definition, and the energy and CO2 methodologies to a series of house designs. Part 1 defines, measures, and establishes a limit for sustainability. It reviews the history of sustainability and sustainable development. A distillation of what is being sought by the various parties to the sustainability debate then contributes to a checklist of essential requirements for a functional definition of sustainability. Addressing climate change is shown to be the major requirement. The checklist enables answers to the questions about measuring sustainability, and knowing when its limit has been reached, and leads to a functional definition: Sustainability meets the needs of the present without annual CO2 emissions exceeding what the planet can absorb. The requirements for sustainability indicator methods are examined. A robust way of comparing environment impacts is introduced. Several common sustainability indicators are examined against the requirements, but are found wanting, while two are found to be effective: energy and CO2 analysis. Human population and annual global carbon absorption are used to identify global and per-capita sustainability limits, which can be applied at many scales to many activities. They are applied to New Zealand's housing sector to identify a sustainable annual per-house emissions target, including construction, maintenance, and operation. Part 2 reviews the methodologies to measure and delimit sustainability using embodied energy and embodied CO2 analysis. A new, fast, accurate, and reliable process-based hybrid analysis method developed for this research is used to derive embodied energy and CO2 coefficients for building materials. Part 3 applies the results of the sustainability definition and limit, and the energy and CO2 methodologies and coefficients from analysing building materials, to a series of house designs within New Zealand and global contexts. A spreadsheet-based calculator developed for this analysis that has potential beyond this thesis is described. A method is presented for annualising emissions to fairly account for differing building components' lifetimes. Finally, a sustainable house is shown to be possible by combining several strategies to meet the challenging sustainable emissions target. Technologies that reduce grid electricity use - solar hot water, PV, and wind-generators - are crucial, cutting emissions the most. Bio-based materials sequestering carbon are the second most important strategy: strawbale insulation to ~R10, and timber for framing, cladding, windows, linings, and roofing. Efficient appliances, lighting, and other low-emission materials were also helpful. Other key outcomes were: hot water heating emits the most CO2, double any other category; heating energy emissions are smaller than any other category; CO2-optimal conventional insulation levels are ~R5; CO2 flux of materials is double operating energy CO2 for sustainable houses.