Chapter 2 Methodology
2.1 The total number of dwellings that benefited from the CHP increased from 8,500 in 2001/2002 to 11,200 in Year 2002/2003, comprised of 5500 private sector dwellings, 4,085 local authority dwellings, and 1635 housing association dwellings.
2.2 The second year sample was drawn to produce statistically reliable information on the impact of the CHP in Scotland at the national level. However, the sample was also designed with a view towards the research project's longer-term requirement to provide statistically reliable data on the changes in fuel poverty:
- for each tenure of the stock;
- for those households with occupants aged under 60 and those 60 or older; and,
- for rural and urban areas.
Results are presented for these various sub-groups within in this report. They are included as indicative of the differential impact of the CHP on those benefiting from the programme. However, because of the small size of some of these data sub-sets, the results for these sub-groups levels are not necessarily statistically reliable, and therefore should be treated with caution. The sample and survey are discussed in more technical detail in Appendix 2.
2.3 The second year total of 11,200 dwellings is comprised of 5500 private sector dwellings, 4,085 local authority dwellings, and 1635 housing association dwellings. The survey sample was drawn by selecting a separate random sample of addresses from each of these three groups. In total,
- 350 addresses were selected from the private sector (with no distinction between owner-occupiers and private rented) (representing about 1 in 16 of the total number of private sector addresses);
- 350 addresses from the local authority sector (representing about 1 in 12 of the total number of local authority sector addresses) and;
- 300 addresses from the housing association sector (representing about 1 in 5.5 of the total number of housing association sector addresses).
Some addresses initially selected were then excluded to ensure that there was no duplication between addresses visited by this monitoring research project and those being visited by the separate health monitoring research project. In total, 31 private sector addresses, 7 local authority addresses, and 38 housing association addresses were excluded.
2.4 Given the number of heating systems installed during the second year of the CHP, and the results from the first year monitoring, the minimum sample size to produce statistically reliable data at the national level was calculated to be 203 dwellings (see Appendix 2). In the end, 475 households were actually surveyed.
2.5 The response rates for the households contacted to participate in the survey, including reasons for not completing surveys, are set out in Table 2.1. A small percentage of the households contacted in each of the three groups refused to participate in the survey. Most of these households did not give a reason for their refusal. The most common reason for not completing a survey was 'no access - no contact', that is, no one was home at the time of any of the visits to the dwelling, and no one responded to the contact card that was left behind by the surveyor. In all three groups, a percentage of the dwellings visited were empty at the time of the survey. A few dwellings were never found because of difficulties with their addresses. The poorest response was amongst the Housing Association sector; the best was amongst the private sector households.
Table 2.1: Survey participation response rates
number of households contact attempted
no access - no contact
refused to participate
address incomplete - could not find dwelling
2.6 Where the household agreed to participate in the research study, the survey involved two separate activities:
- first, an energy survey was completed on the dwelling, with full dimensional data and occupancy data being collected. Importantly, information collected during the survey distinguished between the dwelling's insulation and heating characteristics prior to the CHP improvements, and subsequently. This information was used to complete a Level 3 NHER Surveyor 3 energy audit assessment 8 of every dwelling surveyed, covering both before and after situations, and several different use of heating scenarios.
- second, a household questionnaire was used to collect information on the use and heating of individual rooms, the incidence and extent of condensation in the home, fuel expenditure, methods of payment, self-disconnection, fuel debt, household characteristics, health concerns, and income. All of these issues were differentiated between the period prior to the CHP improvements, and the period after the new heating was installed. This questionnaire interview was completed with an adult in the home. No specific distinction was made over matters such as 'head of household' or 'person responsible for the fuel bill'.
2.7 During the first year survey, the surveys took place between the end of September 2002 to February 2003, with the intention of letting at least 6 months lapse after installation to allow the householders a chance to use the new system. For various reasons, many householders had limited experience of using their new system at the time of the Year 1 survey. To ensure that all householders surveyed had used their heating system during at least one full winter heating season, the second year surveys were conducted between April and August 2004. Some had used it over two heating periods.
2.8 Additionally, during the Year 1 survey, a significant number of households were still awaiting insulation improvements, or even awaiting their first fuel bill because of the changeover in their heating. These matters were not significant issues during the Year 2 survey.
2.9 Importantly, given the purpose of the survey, the words or the term 'fuel poverty' were not used by the survey team at anytime in contacting householders or during the interviews. All contact letters and telephone conversations made reference to the term 'affordable warmth' or the 'affordability of the new heating system'. All surveyors were briefed similarly to use the terms 'affordable warmth' or 'affordability of the heating' during the site visit.
2.10 In total, 475 households were surveyed. Energy audits were completed on all 475 dwellings. The household questionnaire was completed in 474 dwellings. In one dwelling the householder refused to answer any questions after the energy audit survey had been completed. In 21 households (all social sector), the occupants had limited or no experience of heating the dwelling before the new system was installed because they were relatively new tenants.
2.11 The next chapter of this report provides some general information on the households surveyed, prior to the analysis of the information arising from the energy audit and questionnaire survey, which takes up the rest of the report.
2.12 More information on the background to the construction of the second year sample survey is set out in Appendix 2.