Subtropical subdivisions : toward a lot-rating methodology for subtropical climates

Abstract

What role can climatically appropriate subdivision design play in decreasing the use of energy
required to cool premises by maximising access to natural ventilation? How can this design
be achieved? The subdivision design stage is critical to urban and suburban sustainability
outcomes, as significant changes after development are constrained by the configuration of
the subdivision, and then by the construction of the dwellings. Existing Australian lot rating
methodologies for energy efficiency, such as that by the Sustainable Energy Development
Authority (SEDA), focus on reducing heating needs by increasing solar access, a key need in
Australia’s temperate zone. A recent CRC CI project, Sustainable Subdivisions: Energy
(Miller and Ambrose 2005) examined these guidelines to see if they could be adapted for use
in subtropical South East Queensland (SEQ). Correlating the lot ratings with dwelling ratings,
the project found that the SEDA guidelines would need to be modified for use to make
allowance for natural ventilation. In SEQ, solar access for heating is less important than
access to natural ventilation, and there is a need to reduce energy used to cool dwellings. In
Queensland, the incidence of residential air-conditioning was predicted to reach 50 per cent
by the end of 2005 (Mickel 2004).
The CRC-CI, Sustainable Subdivisions: Ventilation Project (CRC-CI, in progress), aims to
verify and quantify the role natural ventilation has in cooling residences in subtropical climates
and develop a lot rating methodology for SEQ. This paper reviews results from an industry
workshop that explored the current attitudes and methodologies used by a range of
professionals involved in subdivision design and development in SEQ. Analysis of the
workshop reveals that a key challenge for sustainability is that land development in subtropical
SEQ is commonly a separate process from house design and siting. Finally, the paper
highlights some of the issues that regulators and industry face in adopting a lot rating
methodology for subdivisions offering improved ventilation access, including continuing
disagreement between professionals over the desirability of rating tools.