Effect of insulating existing houses on health inequality: cluster randomised study in the community

Abstract

Objective To determine whether insulating existing houses increases indoor temperatures and improves occupants' health and wellbeing.Design Community based, cluster, single blinded randomised study.Setting Seven low income communities in New Zealand.Participants 1350 households containing 4407 participants.Intervention Installation of a standard retrofit insulation package.Main outcome measures Indoor temperature and relative humidity, energy consumption, self reported health, wheezing, days off school and work, visits to general practitioners, and admissions to hospital.Results Insulation was associated with a small increase in bedroom temperatures during the winter (0.5°C) and decreased relative humidity (−2.3%), despite energy consumption in insulated houses being 81% of that in uninsulated houses. Bedroom temperatures were below 10°C for 1.7 fewer hours each day in insulated homes than in uninsulated ones. These changes were associated with reduced odds in the insulated homes of fair or poor self rated health (adjusted odds ratio 0.50, 95% confidence interval 0.38 to 0.68), self reports of wheezing in the past three months (0.57, 0.47 to 0.70), self reports of children taking a day off school (0.49, 0.31 to 0.80), and self reports of adults taking a day off work (0.62, 0

Indoor environmental quality benefits of apartment energy retrofits

“…Studies from New Zealand reported improved comfort, indoor air quality (IAQ), and health symptoms resulting from upgrading insulation and replacing ineffective heating systems or heating systems that vent combustion gases to indoors [8,9]. Because pre-retrofit indoor air temperatures were lower than typical temperatures in U.S. homes and because many of the New Zealand homes had heating systems that vented combustion gases indoors, the results of this study are not generally applicable to U.S. homes.…”

Impacts of energy-efficiency investments on internal conditions in low-income households

“…These were pre-post comparisons only, rather than temperature changes relative to control households, but were controlled for external conditions. Howden-Chapman et al (2007) found increases in average bedroom temperatures of 0.50 K and decreases in average relative humidity levels of 2.3% RH (Howden-Chapman et al, 2007). The Glasgow Warm Homes Study (Caldwell et al, 2001) found increases in mean temperatures of more than 2 K for the living room and 3 K for the bedroom.…”

“…Previous research has shown that both insulation and heating measures can increase living room and bedroom temperatures (Caldwell et al, 2001;Howden-Chapman et al, 2007;. Evidence further suggests that energy-efficiency improvements can lower indoor relative humidity levels in both living rooms and bedrooms, and that these effects are greater for more extensive improvements .…”

“…Household monitoring studies are labour and resource intensive, and it may be difficult to recruit large numbers of households to participate in studies. Data-analysis techniques have almost exclusively relied upon averaged or standardized household temperatures to estimate model parameters (Green & Gilbertson, 2008;Howden-Chapman et al, 2007;Richardson et al, 2006;Summerfield et al, 2007). That means that the sample size is effectively limited to the number of households included in the study.…”

The effects of home heating on asthma: evidence from New Zealand

“…The Watcombe housing study conducted in the UK (Barton et al, 2007) investigated self-reported asthma rates in households with improved heating and insulation and found a statistically significant but negligible effect on asthma prevalence. Two prominent randomized controlled studies in NZ looked at the effects of housing improvement on respiratory conditions in general (Howden-Chapman et al, 2007) and asthma specifically (HowdenChapman et al, 2008) and found beneficial causal effects. Crane et al (1998) investigated the effect of installing a Mechanical Ventilation Heat Exchange system on the presence of HDM in NZ homes and found no significant effects.…”