19 Christchurch

Survey details are shown in Table 19.1. The number of households for 2004 was estimated based on 2001 census data for occupied dwellings, extrapolated for 2004 based on Statistics New Zealand population projections. [New Zealand Statistics 2004, www.stats.govt.nz] The latter suggests a population increase for Christchurch of 10% by 2021. [High, medium and low population projections were estimated by Statistics New Zealand. The value used is the medium population projection.]

Table 19.1: Summary survey data, Christchurch

19.1 Home heating methods and fuels

The Digipoll survey was used to collect information on home heating methods and fuels for Christchurch. These data were collected for the purpose of evaluating the impact of variations in heating methods on air quality in Christchurch, in particular the extent of change required to achieve the national environmental standard for PM₁₀. This section presents the results of the home heating survey for Christchurch largely in tabular form, in the expectation that these results will be of value in other assessments (eg emission inventory studies).

Tables 19.2 and 19.3 show domestic heating methods and fuels used for the main living areas in Christchurch houses, and seasonal variations in heating behaviour. The commonest method of heating the main living area in Christchurch was electricity, which was used by 72% of households. Many households used more than one method of heating in their main living area.

The primary area of difference in home heating methods for Christchurch was the low use of solid fuel burning for domestic home heating. In particular, the use of wood burners is low at 19% of households compared to a national average of around 38%. Previous surveys for Christchurch (Lamb, 1999 and 2003) [Lamb C. 1999. Christchurch Home Heating Survey: A survey of domestic home heating methods and fuels in the Christchurch metropolitan area. Prepared for Environment Canterbury. Report U00/34; Lamb C. 2003.2002 Christchurch Home Heating Surveyprepared for Environment Canterbury.] have shown higher proportions of households using wood burners (34% and 30%, respectively). Although some reduction in wood burner numbers is expected as a result of the city's Clean Heat Programme, the impact of this is estimated to be a reduction in solid fuel burners of around 1920 (2400, less 20% using solid fuel replacement methods). By contrast, this survey suggests a decrease in solid fuel burners of over 15,000 wood burners since 2002. While possible, this would seem unlikely and the possibility of heating method bias in households refusing to answer the survey questionnaire should be considered. That is, a greater proportion of households with wood burners may have refused to answer the survey questionnaire relative to households with other heating methods. This is highly feasible as awareness of the impact of heating methods on air quality in Christchurch is likely to be greater than for most areas, and households may be concerned about regulations relating to heating methods proposed in the Regional Air Plan.

Table 19.2: Domestic home heating methods and fuels, Christchurch

Around 4% of households using wood burners and 14% of households using open fires indicated that they operated them during the summer months, burning three to four times a week. Gas was also used for heating during the summer months by around 9% of the households using that method (Table 19.3). Table 19.4 shows that the average quantities of fuel burnt per day per household are typically less during the non-winter months than during the winter. Data are not presented for all heating methods because there was a high non-response rate for questions relating to seasonal variations for some heating types.

Table 19.3: Monthly variations in heating behaviour and fuel use, Christchurch

Table 19.4: Estimated daily fuel use, by season, Christchurch

19.2 Insulation, cost of heating, income, and house age and size

In addition to collecting data for the purpose of evaluating the impact of variations in heating methods on air quality, information was collected on a number of variables relevant to the Ministry for the Environment's Warm Homes Project. Relevant data for Christchurch are presented in this section.

Figure 19.1 shows that the proportion of households using gas systems that are properly flued in Christchurch is similar to the national average (32% in Christchurch compared with 28% in the national survey).

The amount spent on heating for a winter month, by heating method, is shown in Table 19.5. In Christchurch, households heating using open fires spent on average less per month (around $40) than those using other heating methods.

Figure 19.2 shows the average heating costs, home ownership, age of dwelling and number of bedrooms for households in Christchurch. Around 43% of respondents were living in rented accommodation. The most common method of heating rental accommodation was electric. One factor influencing the amount spent on different heating methods is the ability of households using solid fuel burners to obtain wood free of charge. Figure 19.3 shows that a large proportion of the wood used on solid fuel burners in Christchurch is self-collected.

Figure 19.1: Distribution of flued versus unflued gas heating and age of wood burner, Christchurch

Table 19.5: Average monthly heating costs (winter), Christchurch

Figure 19.2: Domestic heating method, by average monthly heating expenditure, house ownership, house age and number of bedrooms, Christchurch

Average heating cost per month (winter)

House ownership

Age of dwelling

Number of bedrooms

Figure 19.3: Proportions of fuel obtained free of charge versus bought, Christchurch

Table 19.6: Type of electric heating, Christchurch

The commonest types of electric heating used in the main living area in Christchurch houses were oil column heaters and fan heaters (Table 19.6). The proportion of houses using the more efficient heat pumps was 13%, which is the same as the national average.

Data on home heating methods, by house ownership, are shown in Table 19.7.

Table 19.7: Home heating method, by house ownership, Christchurch

Household insulation types and heating methods are shown in Tables 19.8 and 19.9. Around 18% of households in Christchurch indicated that the house had no insulation. This compares with a national average of 10%. Table 19.10 shows home heating method, by household income. The overall non-response rate was around 28%. This limits the interpretation of these data because there may be an income bias in the non-respondents.

Table 19.8: House insulation summary statistics, Christchurch

Table 19.9: Degree of house insulation, by heating method, Christchurch

Table 19.10: Home heating method, by household income, Christchurch

Tables 19.11 and 19.12 show the relationship between heating methods and the age of the dwelling and number of bedrooms, respectively.

Table 19.11: Home heating method, by age of dwelling, Christchurch

Table 19.12: Home heating method, by number of bedrooms, Christchurch