Abstract
New Zealand homes are typically colder in winter than the World Health Organisation's recommendation of 18C. Cold homes are associated with a number of poor health outcomes, particularly respiratory and circulatory illnesses. Reducing exposure to cold homes would plausibly simultaneously improve comfort and reduce health related costs for both the individuals and the health care system.
This research aimed to investigate some of the main causes for cold homes and help to provide evidence about which pathway/s might be most amenable to successful intervention.
Two modelling studies and a randomised controlled trial were used.
The effect of house quality was examined through house plans. The joint effect, over decades, on the heating energy requirements of typical dwellings were modelled as a consequence of changes to the thermal quality regulations regarding buildings in New Zealand, and the changes in building size. This study found that the although the initial requirement for insulation in the 1970s had reduced required heating energy, subsequent increases in thermal requirements resulted in little further reduction in required heating energy because houses had become larger on average.
The ability of households to pay off energy efficiency home improvements was examined by modelling the effects of changes in the price of electricity. The specific price changed modelled was the proposed removal of the low fixed-user-charge tariff. This study found that the tariff removal would effectively increase the price of electricity for low electricity users and increase the length of time required by many households to pay off any home energy efficiency improvements.
The effects of household income and spending on fuel were examined through a randomised controlled trial of 522 participants over the age of 55 with Chronic Obstructive Pulmonary Disease. A $500 electricity voucher was placed in the electricity accounts of participating households during either the first or second study winter. Household electricity use, temperature and health outcomes were measured. This study found that providing the electricity voucher increased the electricity use over winter, especially for households with low initial use. However, the increased electricity use was much less than the full value of the voucher. There was some evidence for increased home warmth, especially a reduction in exposure to cold or very cold temperatures. The evidence for change in health was equivocal, with no improvement in the primary outcome, the number of moderate or severe exacerbations the participants experienced; but there was some evidence of a decrease in mortality rates.
Each of the different pathways examined could plausibly improve home warmth to some degree if an appropriately sized intervention was implemented. However, fiscal, political and climate constraints make it unlikely that the cost of fuel can be fully controlled. The voucher was successful at increasing electricity use, especially among those with low initial use, so may be most useful as a targeted intervention. The most feasible pathway to improved home warmth is through increasing the thermal quality of dwellings.