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Life Cycle Assessment of a New Zealand house

This study examines the life cycle of a "exemplar house" in New Zealand, comparing six design alternatives and analyzing their environmental impacts over a 50-year period. The goal is to identify the hot-spots and improve the environmental performance of residential buildings.

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Life Cycle Assessment of a New Zealand house

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  1. Life Cycle Assessment of a New Zealand house Barbara Nebel & Zsuzsa Szalay Scion

  2. “exemplar house” • Specifically designed as an example for research on residential costing (Willson 2002) • two storey design • three bedrooms and a garage • total floor area of 195 m2

  3. Building construction • suspended timber floor with foil / concrete slab on ground floor; • Light timber frame walls with fibre glass insulation, plasterboard internal lining with paint finish, external cladding weatherboard/ fibre cement/ brick; • pitched timber truss roof, flat ceiling with insulation lined with plasterboard, steel cladding/concrete tiles; • aluminium frame windows without thermal break.

  4. Life Cycle Assessment Framework Goal and scope definition • Direct applications: • Product development and improvement • Strategic planning • Public policy making • Marketing • Other Inventory analysis Interpretation Impact assessment Life Cycle Assessment

  5. Goal and Scope • Develop a generic LCA model for houses for research purposes • Compare six design alternatives • Find the environmental hot-spots • Analyse embodied and operational environmental impacts Functional unit: the Exemplar house over a 50-year period in New Zealand

  6. Scenarios • Six design alternatives • Three heating fuels: wood, gas, electricity • Three locations: Auckland, Wellington, Queenstown

  7. Data • Average data from Europe • for New Zealand only embodied energy and CO2-emissions are available (Alcorn) • Data gaps: • Dataset for carpet was based on GaBi data and a European study (Potting 1994) • Timber treatment is missing

  8. Maintenance • Life time of building is 50 years • Average life time of building elements based on New Zealand and European data • Prorating was applied due to the high level of uncertainties • Life time of building element is 20 years • Number of replacements: 50/20 -1 = ? 1.5

  9. Operation • Hot water, ventilation, cooling, lighting, appliances not considered • Heating energy calculated with ALF3 (BRANZ) • heating levels: 16, 18, 20 °C • heating schedules: evening, morning and evening, all day, 24 hour heating • Insulation as required by NZ Building Code

  10. GaBi model

  11. Production

  12. Heating energy demand Evening heating, 18°C 24 hour heating, 20°C

  13. Thermal mass

  14. Impact categories • Non-renewable energy demand • Renewable energy demand • Global warming • Ozone depletion • Eutrophication • Acidification • Photo-oxidant formation

  15. Building materials

  16. Building elements

  17. Wall components

  18. Foundation and floor

  19. Roof components

  20. Life cycle energy

  21. Life cycle energy Timber/ WB/ steel

  22. Environmental impacts Timber/ WB/ steel, Wellington Gas heating Timber/ WB/ steel, Wellington Electric heating

  23. Transport distances 100 km - 50 km - 200 km

  24. Useful life of carpet 10 years – 8 years – 15 years

  25. Conclusions • For typical New Zealand heating level and schedule, materials have significant influence on life cycle results • Interesting results relating to thermal mass in intermittent heating schedule • Materials need to be looked at on component level • LCA is good tool to optimise building design • Tool can be used for other house designs based on data from quantitiy surveyor

  26. Outlook • New Zealand inventory data for building materials • Insulation scenarios: NZS better and best practice • Statistical model to represent current building stock • Model retrofit of an existing house with insulation in walls

  27. Futher information Barbara Nebel, PhD Groupleader Sustainability Framworks Sustainable Consumer Products Private Bag 3020, ROTORUA, New Zealand Phone +64 7 343 5637 Email: Barbara.nebel@scionresearch.com

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