The Watcombe housing study: The short-term effect of improving housing conditions on the indoor environment

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Abstract

A three-year study (1999–2001) was initiated in the UK to assess the effect of improving housing conditions in 3–4 bedroom, single-family unit, social rented sector houses on the health of the occupants. The houses were randomised into two groups. Phase I houses received extensive upgrading including wet central heating, on demand ventilation, double-glazed doors, cavity wall and roof/loft insulation. An identical intervention for Phase II houses was delayed for one year. As part of this randomised waiting list study, discrete measurements were made of indoor environmental variables in each house, to assess the short-term effects of improving housing conditions on the indoor environment. Variables representative of indoor environmental conditions were measured in the living room, bedroom and outdoors in each of the three years of the study. In 2000, there was a significant difference between the changes from 1999 to 2000 between Phase I (upgraded) and II (not then upgraded) houses for bedroom temperatures (p = 0.002). Changes in wall surface dampness and wall dampness in Phase I houses were also significantly different to the change in Phase II houses in 2000 (p = 0.001), but by 2001 the Phase I houses had reverted to the same dampness levels they had before upgrading. The housing upgrades increased bedroom temperatures in all houses. Other indoor environmental variables were not affected.

Introduction

There is a growing understanding that the indoor environment, particularly indoor air quality, can affect health (IEH, 2001, JRC, 2003, NAS, 2000) and that personal exposure to pollutants can often be greater indoors than outdoors (Clayton et al., 1993). Several indoor environmental variables are commonly cited as having an association with health. Cold homes in the UK have been associated with increased cardio-respiratory mortality and morbidity (Press, 2003). The UK Department of Health has recommended that temperatures should be 18–21 °C in living rooms and 18 °C in bedrooms to improve comfort and prevent health problems (DTI and DEFRA, 2001). Dampness and relative humidity indoors are indirectly associated with health (NAS, 2000). If relative humidity is outside the optimal range for humans of 40–60% this can lead to health problems linked with increases in the ideal conditions for bacteria, mould and dust mites (Sterling et al., 1985). Health problems associated with dampness are mostly due to the relationship with mould growth and other microbes. The only recommended limit available for dampness relates to the prevention of visible damp, mould growth or structural damage (Protimeter plc, 2001). The limit is represented as a wood moisture equivalent (WME%), which should be ≤ 20%. There are no recommendations for safe indoor levels of microbial colonies in dwellings, despite the fact that there is evidence of negative health effects from mould in the home (Lugauskas et al., 2003) and known toxic properties of mould by-products (NAS, 2000). The presence of some bacterial colonies, e.g. Legionella pneumophila (Legionnaire's disease), indoors are a concern because of the spread of infection.

The indoor allergen most commonly associated with health, particularly the exacerbation of asthma and allergies is Der p 1, from the dust mite species Dermatophagoides pteronyssinus (NAS, 2000). There is an international recommendation to limit Der p 1 to ≤ 2.0 μg g 1 to prevent sensitisation (WHO, 1988). The World Health Organisation gives a limit for absolute humidity ≤ 7.0 g kg 1 to reduce the proliferation of dust mites (WHO, 1988). Furred and feathered pets are also a major source of allergens indoors. In particular, cats (Felis domesticus) produce Fel d 1, which can exacerbate asthma (van der Heide et al., 1999).

Respirable fine particles with an aerodynamic diameter < 2.5 μm infiltrate from outdoors, with indoor sources mainly originating from tobacco smoking and cooking activities (Abt et al., 2000, BéruBé et al., 2004). Respirable particles penetrate into the deep lung and are associated with chronic inflammatory processes (EPAQ, 2001). Environmental tobacco smoke is a serious health burden, especially for children (Kabesch and von Mutius, 2000). Inhalable coarse particles with an aerodynamic diameter > 2.5 μm, include allergenic particles, such as pollen, fungal spores, broken up dust mite faeces and dander. No threshold values are given in the UK for particulate numbers, concentrations or particle size distributions in dwellings. The UK Health and Safety Executive has set limits for occupational exposure to dust (time weighted averages) to 10 mg m 3 8 h for inhalable dust and 4 mg m 3 8 h for respirable dust (HSE, 1995). Some studies have shown that there is a stronger relationship between numbers of particles and health as opposed to particle mass (Maynard, 2000), hence the measurement of numbers of particles in this study.

The study was conducted in Watcombe, an estate of social rented sector properties in Torquay, UK. A self initiated survey by the residents revealed that many of the houses had damp and mould problems (64%) and high levels of health problems, particularly breathing related (60%). Therefore, Torbay Council agreed to upgrade the Watcombe houses. The Torbay Healthy Housing Group was formed to evaluate the impact of these non-compulsory, non-contributory housing upgrades on the indoor environment of the houses and the health and well being of the occupants (Somerville et al., 2002). The estate was built during 1939–1940, in a wide shallow valley, in a coastal area with minimal industrial airborne pollution. The houses were of sound construction, semi-detached or terraced, single-family, two storey buildings with 3–4 bedrooms (∼53 m3 occupant 1).

The study reported here is one of the first studies that has measured environmental and health outcomes as part of a rigorously designed evaluation of housing improvements in the UK.

Section snippets

Study design

Ethical approval for the study was given by the Torbay Local Research Ethics Committee. Houses were randomly allocated to be upgraded in 1999 (n = 50, Phase I) or 2000 (n = 69, Phase II). The Phase II houses acted as a control for the Phase I houses to assess if there had been any changes in the indoor environment between 1999 and 2000 attributable to the upgrades alone.

Intervention

The houses had an average minimum Standard Assessment Procedure (SAP) energy rating for dwellings (DEFRA, 2001) of 38 before

Randomisation

Randomisation produced two groups with similar characteristics (Table 2). Differences between the two Phases in the following results are attributable to the intervention, not to differences at baseline.

Response rates

Acceptance of the environmental survey was high, with 97% (1999), 96% (2000) and 88% (2001) of households agreeing to participate.

Indoor environmental outcomes: comparison between groups at 2000

The means for each variable recorded in each year are given in Table 3. The change in bedroom temperature in Phase I houses was significantly different from that of

Discussion

Over the three years of the study, the intervention produced substantial improvements in the energy efficiency of the houses, as demonstrated by the increase in SAP ratings. There was an increase in bedroom temperatures linked to housing upgrades, with a significant difference between phases in 2000. The housing upgrade increased the percentage of houses meeting the minimum government recommendation of 18 °C, from 23% to 75% and significantly reduced the difference between the living room and

Conclusions

The housing upgrades produced a substantial increase in the energy efficiency of the houses and an improvement in thermal comfort as an immediate result. The extent to which such upgrades can be expected to improve the indoor environment may be limited, as occupants, their habits and indoor activities remain substantially the same and influence the variables measured. Improving housing through energy efficiency interventions may not have a measurable impact on the indoor environment apart from

Acknowledgements

The authors would like to thank the residents of the Watcombe estate for their time and patience in participating in this study and the NHS (SW) R and D for funding the evaluation of the housing upgrades.

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