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64 PROPOSAL TO REVISE ENERGY EFFICIENCY REQUIREMENTS OF THE BUILDING CODE OF AUSTRALIA FOR COMMERCIAL BUILDINGS
Energy savings were estimated by comparing the annual energy use
predictions for buildings modelled to be just compliant with the BCA 2009
DTS requirements (also referred to as the ‘baseline’) against buildings
modelled to be just compliant with the proposed BCA 2010 DTS
requirements. 24
Reduced energy consumption
The estimated impact of the amendments on energy consumption is
reported in tables 6.1 (expressed in MJs per m 2 ) and 6.2 (expressed in
percentage terms). The tables report the average annual change per
square metre of gross floor area, for gas and electricity. These estimates
take account of the fact that each of the proposed measures is likely to
have different effective life spans. 25
To estimate energy savings, the ABCB provided TheCIE with results of
thermal performance modelling which illustrated the likely impacts of the
proposed amendments on building energy consumption. The ABCB
assumes that the amendments will only affect a building’s consumption of
electricity — with the exception of changes in energy required for heating.
Any changes to building heating are assumed to be gas. (Note that table
6.1 indicates that for some buildings gas, consumption actually increases
— this reflects a switch in the fuel mix.)
The reported per cent changes to gas consumption should be interpreted
with caution. In proportional terms, the amendments might induce a large
reduction in gas consumption — but buildings use relatively little gas
compared to electricity. It is not uncommon for the amendments to reduce
total energy consumption by 20 per cent or more. This type of effect is
consistent with the amendments’ objectives. From an abatement
perspective, the demand for gas is preferred to electricity because it is less
GHG intensive. From an energy efficiency perspective, the total change in
energy use is the leading indicator.
The predicted savings in total energy consumption are seen to be positive
in all cases; varying from 5.6 per cent in Thredbo (climate zone 8) for the
2-form office building (single storey, light-weight building) to 39.7 per cent
24 That is, it is not assumed that buildings exceed the required energy efficiency
performance as specified in the 2009 and proposed 2010 BCA, for the BAU and
change scenario respectively.
25 For example, mechanical ventilation assets will have an effect that last the entire life of
the building. In contrast, lighting will require replacement every 7 years, resulting in a
much shorter effective lifespan.
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