Data sources on the existing housing stock

Data on the housing stock in Australia are distributed across various government surveys and national statistics. The Census provides basic

information on the number and types of dwellings for states and territories and suburbs (Australian Bureau of Statistics, 2012d). The Survey of Income and Housing (SIH) includes information for Australian households on dwelling structure and condition (Australian Bureau of Statistics, 2009c). The Australian Housing Survey reports on the construction material and the building services provision for housing (Australian Bureau of Statistics, 1999). The

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characteristics of Australian homes and implications for household energy use and greenhouse gas emissions are presented in Energy in Focus; Energy Efficiency in Australian Homes (Australian Bureau of Statistics, 2010d). Data on the quantum of work done in residential building, including alterations and additions, may be obtained from the quarterly Building Activity Survey (BAS) and National Accounts, both published by the Australian Bureau of Statistics (ABS). National statistics for energy consumption are available from the Australian government by fuel type at the national and state levels in Energy Account published by the ABS, and Energy Update published by Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES).

Data in relation to how households use and conserve energy are available through Environmental issues: Energy Use and Conservation Survey (Australian Bureau of Statistics, 2008; 2011c) and to a more limited extent, through surveys such as the Greenlight survey of householders in Victoria (Sustainability Victoria, 2011).

As well as government sources this analysis is supplemented by published data from non-government sources including the Housing Industry Association (HIA). Data on the housing stock in Victoria is also drawn from the Valuer General of Victoria (VGV) unpublished dataset 2008, which is the most

comprehensive survey available on the dwelling stock in Victoria and provided the most up to date property information available at the time. The next section considers the main sources of data and their limitations.

2.3.1 Census of Population and Housing

The Census of Population and Housing collects a range of demographic, social and economic information from all people and dwellings² in Australia including the number of people, their key characteristics, and the dwellings in which they live. Conducted every five years, the most recent Census was conducted on 9 August 2011.Core demographic data items were released on

2 Excluding diplomatic personnel and dwellings.

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21 June 2012 with other data requiring more detailed processing scheduled for release after this date. Whilst the census identifies numbers of dwellings in Victoria by type of structure (classified as separate house, semi-detached, unit or apartment, and other), and numbers of bedrooms, this does not provide detailed information about the age and construction of dwellings, which are important factors influencing energy performance (see section 2.4.2).

2.3.2 Australian Housing Survey

The most recent Australian Housing Survey was conducted between

September and December 1999³ to report on the housing circumstances of Australians. Previous surveys covering similar material were known as National Housing Surveys, and were conducted in 1988 and 1994. Although these surveys collected information on dwelling characteristics including information on the physical characteristics and condition of dwellings, this is now dated, and many dwellings may have been upgraded or extended in the intervening period.

2.3.3 Building Activity Survey (BAS)

Statistical information on building activity is collected quarterly by state and territory for new residential buildings (houses and other residential), and alterations and additions to dwellings. Data series are shown in seasonally adjusted and trend terms, while the value of building work commenced and done is also shown in chain volume measures terms. The statistics are compiled using building approval details and returns collected from builders and other individuals and organisations engaged in building activity. However, the quarterly estimates only include residential building jobs valued at $10,000 or more. As the estimates for building activity (including alterations and

additions) are based on a sample of approved building jobs, they are subject to sampling error; that is, they may differ from the figures that would have

3 According to EES & DEWHA (2008) the last major survey of housing characteristics undertaken by the ABS (ABS 8212.0) was in 1986.

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been obtained if information for all approved jobs for the relevant period had been included in the survey.

2.3.4 Australian National Accounts

A further important data series published by the ABS that can be used to observe the trend in alterations and additions is taken from the National

Accounts measurement of Gross Fixed Capital Formation (GFCF) in dwellings where expenditure on fixed assets is broken down into two sub-categories:

new and used dwellings, alterations and additions. The method used to calculate residential alterations and additions starts with the BAS. Since a significant proportion of alterations and additions are not captured in the BAS, it is used as a benchmark, which is then extended by use of estimates of expenditure on alterations and additions drawn from the Household Expenditure Survey (Dalton et al., 2008).

2.3.5 Rating Valuations Survey

The Valuer General of Victoria (VGV) oversees the collection of valuation data every two years by municipal authorities under the provisions of the Valuation of Land Act 1960 (as amended 15 December 2009). The statewide survey provides authoritative data on each individual rateable property in Victoria. As part of the valuation process, each property is surveyed and desk-based market valuations are undertaken. As part of the exercise, details about each building are recorded, including approximate date of construction, size, type of dwelling, construction materials and condition. Since this includes every

residential dwelling and is based on a survey by a qualified valuer this data is likely to be more reliable than the ABS data. While the VGV 2008 dataset has a high level of coverage, it also has limitations. It does not include specific information on heritage status. The dataset contains millions of records with great variation in data formats, including inconsistencies in recording data.

Analysis was undertaken as part of this study but not all records could be