25
greater understanding of buildings because now
developers, signing up to NABERS commitment
agreements would pass the commitments on to
the builders to deliver their ratings. This provided
the framework for designers to be able to verify the
simulated design of the buildings against the actual
performance.
This greater understanding of buildings threw up
some anomalies in the thinking of the time. For
instance, through detailed modelling it was found
that, for a commercial office building in Sydney
a single low e laminate could perform better
in overall energy consumption than a double
glazed unit (DGU). Therefore and from an energy
perspective only, the best type of glass you could
specify for an office building in Sydney was a low
e laminate. Within the BCA 2006 there were five
methodologies put forward to use as verification
of a complying development. These were; Deemed
to satisfy (DTS), 3 verification methods, alternative
solution and lastly expert opinion.
As part of the DTS a glazing calculator was
introduced. This calculator provided two methods
with which to calculate the solar exposure against
a stated threshold. Many projects could use either
method in the beginning with varying answers.
This led to inconsistencies in the results leading to
confusion and eventually method 1 was scrapped.
2006 – 2007 issues of the BCA had two verification
methodologies to choose from for classes 3-9
(BCA JV2 or JV3). JV2 allowed for a building
to be modelled against a stated value for its
class. This methodology was an easier way to
achieve compliance than JV3 and as a result
lower performing glass systems could be used.
If solutions could not be found using the DTS
calculator then JV2 was the preferred methodology
Slowly the performance requirements of the
envelope were being tightened and in 2008 BCA
JV2 was scrapped. For any complex building form,
JV3 methodology was becoming the preferred way
to reach compliance.
2010 saw a significant increase in the performance
requirements of the DTS glazing calculator. You
could no longer blindly go through the planning
approval process and hope that there would be a
glazing manufacturer that would have a glass type
that would suit your purpose. A dialogue opened up
with project managers, developers and architects.
Rather than waiting for construction certificate (CC)
to assess the envelope for compliance, a quick check
was essential at development application (DA). The
last thing anyone wanted was to pass through DA only
to find that there was no commercially available glass
around that would satisfy the results from the glazing
calculator. A reduction in glass area would ultimately
result in a resubmission of the DA to council and a
programme delay and embarrassment for the design
team.
In the commercial sector the difference between a
façade performance required to achieve a NABERS
4.5 rating and a BCA compliant façade was reduced
significantly due to these new changes in the BCA
2010. Thermally broken frames were introduced from
Europe which significantly improves the U-values of
the window and the resulting heat gains/losses. The
introduction has been slow due to cost but finally
they are gaining traction.
We have seen more of a reliance on automated
façade elements to compliment the high
performance glazing types in the last few years,
particularly on commercial buildings. These façade
types come at a premium, but they do start to assist
in providing a façade solution that achieves more
than just energy efficiency. A good façade should
provide thermal comfort for the occupants, high
levels of daylight and