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The cost effectiveness of housing thermal performance improvements in avoiding CO2- emissions


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McLeod, P (2013) The cost effectiveness of housing thermal performance improvements in avoiding CO2- emissions. PhD thesis, University of Tasmania.

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It is widely recognised that the built environment is a significant contributor to
greenhouse gas emissions worldwide. In Australia, to reduce the greenhouse gas
emissions associated with new houses, energy efficiency provisions were introduced into
the Building Code of Australia (BCA). The primary focus of the regulations has been on
achieving thermal comfort through a reduction in the energy houses require for heating
and cooling (space-conditioning energy). A star rating system is used to indicate the level
of thermal performance a new house achieves. Ratings range from 0 to 10 stars and
theoretically, the higher the star rating the less space-conditioning energy a house
requires. Currently, all new houses built in Australia require a minimum of either a 5 or 6
star rating, depending on the state/territory, with the required minimum level expected to
increase incrementally in the future.
It is widely claimed that there are considerable opportunities for cost effective greenhouse
gas abatement in the residential building sector. However, the claims generally neglect to
take into account any increase in embodied energy (and associated emissions) that may
result from implementing those opportunities. Increasing a house’s thermal performance
generally increases its embodied emissions. Current research findings indicate that
embodied energy and its associated emissions can contribute significantly to a house’s lifecycle
energy and CO2-emissions, with that contribution increasing the more thermally
efficient a house becomes.
The aim of this research was to determine and rank the cost effectiveness of a wide range
of thermal performance improvements, for houses with ratings from 4 to 8 stars, taking
into account their embodied emissions. To achieve this, several project homes constructed
in Tasmania whose size and floor plan varied were selected. Using thermal simulation
software the space-conditioning energy requirements of the thermal performance
improvements were calculated. The cost of each thermal performance improvement was
estimated and the resulting increase in embodied energy calculated. For each house, timber
floor and slab-on-ground designs were modelled. The same thermal performance improvements were made to each house. These were
ranked for their cost effectiveness in reducing space-conditioning emissions, minimising
the increase in embodied emissions and reducing net emissions. For each measure of cost
effectiveness, the rankings were compared to determine the effect house design and house
size had on the results.
The results show that the cost effectiveness of achieving pre-determined levels of thermal
performance varies significantly depending on the methods and materials used. There are
numerous methods that can be used to improve the thermal performance of a house to a
certain level, with costs varying significantly. While generally the most and least cost
effective designs in minimizing embodied emissions are the same for each house, some
design differences between the houses are a significant factor in determining how cost
effective improvements will be in minimizing embodied emissions. In terms of cost
effectiveness in reducing net emissions the results show that for lower star band ranges
(5-6 star), the most cost effective designs in reducing net emissions are also the most cost
effective in saving space-conditioning emissions. However, in the higher star band
ranges cost effectiveness in saving space-conditioning emissions cannot be used to
predict reliably the cost effectiveness in saving net emissions. Finally, the results shows
that while heating appliance type and efficiency do not affect cost effectiveness rankings,
the choice of heating appliance is significant in determining whether an increase in
embodied emissions outweighs a decrease in space-conditioning emissions and at what
level of thermal performance that occurs.

Item Type: Thesis (PhD)
Keywords: housing, cost, thermal performance, CO2-e
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Date Deposited: 02 Oct 2013 03:00
Last Modified: 15 Sep 2017 01:06
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