Abstract
This paper reports the results of a study on the cost implications of achieving greater energy efficiency as measured by House Energy Rating(HER) ‘stars’ for new housing on a greenfield development in the northern suburbs of Adelaide. Twelve house designs typical of the housing options available from a number of builders engaged with this development were modeled using the 2nd generation Building Code of Australia (BCA) accredited energy rating assessment tool AccuRate. Where the model predicted a rating below the minimum rating (6 star) proposed under the recently agreed Commonwealth of Australia, National Energy Efficiency strategy, the designs were modified in order to improve the rating to 6 stars using a combination of specification changes and energy efficient technology options. These changes or options were then priced at prevailing building suppliers and subcontractors retail cost levels in order that an average ‘extra cost to 6 star’ and range of indicative costs to achieve 6 star housing compliance could be articulated. The results revealed that standard and currently available technologies, such a reflective foil barriers, increased insulation and low emissivity ‘e’ type glazing provide a means to achieving 6 star ratings at a modest additional cost, i.e. 1-2% of total construction and development costs.
Highlights
In Australia, the regulation of energy efficiency of buildings is covered by a range of Commonwealth, State and Territory agencies
The classification of houses situated in Playford North for climate data purposes under the National Home Energy rating system (NATHERS) is Climate zone 16 (Adelaide) and the relevant energy consumptions are respectively 125 and 96 MJ/m2 for 5 and 6 stars.an increase from 5 to 6 stars represents a reduction of 23% in the energy demand of a house in the Adelaide climate zone
The study of Adelaide houses shows a range of indicative costs at an average of cost increase to achieve 6 stars of some $3,150
Summary
In Australia, the regulation of energy efficiency of buildings is covered by a range of Commonwealth, State and Territory agencies. The modeling of improved building envelope thermal performance was limited in scope to typical temperate climate modifications around the elements of wall and roof insulation and glazing as has been shown in a number of recent studies by Constructive Concepts Pty (2009) and earlier by Burghardt (2008) to improve thermal performance in Australian housing and dwelling units The focus on these elements is supported by the prescriptive deemed to satisfy (DTS) measures for energy efficiency as adopted by the Australian Building Codes Board (2009). Fricker (2002) in his study shows that the benefit of additional insulation levels is non linear and diminishes once high levels of insulation are ‘standardised’ into housing and a recent report by the Australian Window Association (2009) into the changes to a 6 star energy rating for residential buildings points to a requirement for high performance glazing as this insulation benefit reduces. For Adelaide housing (Zone 5) the appropriate area adjustments used by the software in energy load calculations are: 50m2 1.2
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