Research and Policy
Energy Efficiency and House Usage in Fordlands - April 2008
The Energy Efficiency and House Usage evaluation reviewed interventions undertaken in an upgrade programme as part of Housing New Zealand Corporation's Fordlands Community Renewal project. The evaluation found that insulation of external walls increases the overall energy efficiency of houses and is associated with tenants' positive perceptions about household warmth and dryness. The results are consistent with aspects of Otago University's work in He Kainga Oranga, the Housing and Health Research Programme being undertaken at Wellington School of Medicine.
Research purpose and approach
The aim of this evaluation was to investigate energy efficiency interventions and house usage to enable Housing New Zealand to improve its interventions for tenants. The evaluation used sensor monitoring, householder interviews and staff interviews to investigate:
- the marginal benefits of insulating external walls and installing thermal drapes
- energy efficiency interventions and house usage.
The conclusions from this evaluation are indicative only, due to the small sample sizes used.
Key Points
- According to sensor monitoring data and householder interviews, external wall insulation had a positive effect on house temperatures and humidity.
- Tenants reported some awareness of effective heating, ventilation and other energy-efficient practices.
- Tenant awareness can be enhanced through the introduction of a wider range of energy-efficient practices.
- Evaluation findings are consistent with information gathered from He Kainga Oranga's Housing, Heating and Health Study of Housing New Zealand tenants.
Findings
- The sensor monitoring data suggested that external wall insulation had a positive effect on house temperatures and humidity. The statistical analysis involved testing the sensor monitoring data for "effectiveness" rather than "significance" because the data requirements for significance testing were not fulfilled. The analysis showed that compared to homes without external wall insulation, homes with external wall insulation were on average one degree centigrade warmer and nearly five percent less humid. One degree centigrade warmer equates to a statistical effect of 0.67 which is a medium to large effect. Five percent less humidity equates to a statistical effect of 1.06 which is a fairly large effect.
- This statistical analysis was supported by information gathered through householder interviews, which suggested that external wall insulation has a positive effect on tenants' perceptions of house dampness and warmth.
- Where thermal drapes are fitted, they are used regularly by tenants.
Effective heating sources include enclosed fireplaces and wood pellet burners. Ineffective heating sources include open fires, unflued gas heaters, and fixed or portable electric heaters.
- Tenants showed some awareness of the importance of effective heating although they reported using less effective heating in addition to, or instead of, in-built effective heating. This suggests there may be opportunities for education.
- About half of the tenants reported that their houses were colder than they would have liked. They used non-heating methods to get warm as well as, or instead of, heating; for example, having a hot bath, wrapping in a blanket, or going to bed.
- Tenants valued heating affordability highly. Following insulation retrofitting, however, tenants tended to prioritise increased warmth over saving money.
- Most tenants reported using at least some effective ventilation practices. Where ventilation equipment was installed (such as range hoods), tenants tended to use it. However, installation needs to be supported by education on the function and use of upgraded ventilation features.
- Householders who had received external wall insulation appeared more likely to change their heating and ventilation behaviour following insulation retrofitting.
- All participants reported using some energy-efficient practices. There may be scope, however, for further education with tenants about a wider range of energy-efficient practices, including reducing shower times and using the washing machine for full loads only.
- The evaluation results are consistent with the Housing, Heating and Health Study which is part of He Kainga Oranga, Otago University's Housing and Health Research Programme. This study indicates that when houses are insulated, energy usage is reduced and householders report increased warmth and less visible mould (evidence of dampness). The evaluation findings suggest that there may be a marginal benefit in insulating external walls in addition to ceiling and under floor insulation.
- Analysis of sensor monitoring data indicates there is no compelling evidence to link relative humidity and heater type. This is consistent with the He Kainga Oranga study.
- Evaluation findings about heating and ventilation values and preferences are consistent with information gathered from the households of Housing New Zealand tenants for the He Kainga Oranga study.
Implications for policy and programme development
The evaluation provides information to the Community Renewal programme for decision-making about the costeffectiveness of options for retrofit upgrades and tenant education. The evaluation has contributed information to the Cross Departmental Research Project on Fuel Poverty that will commence in July 2008.
Further Information
This paper is based on the report, Energy efficiency interventions and house usage: An evaluation of energy efficiency initiatives undertaken by Housing New Zealand' Fordlands Community Renewal Team. Prepared for Housing New Zealand by Diana Beattie (March 2008).
Other related reports include: Housing, Heating and Health Study: Comparisons of characteristics of HNZC houses and households with non-HNZC houses and households. Prepared for Housing New Zealand by Philippa Howden-Chapman and David Shields of Otago University's He Kainga Oranga/Housing, Heating and Health Study (August 2007).
