Warm, dry houses are healthier

This Issue This is a part of the Buildings and health feature

By - , Build 108

It is one thing to say that health improvements follow once a house is made warmer and drier, but much harder to prove this conclusively and scientifically. Two major research projects set out to do just that and have shown the benefits of well-insulated, warm houses.

The Housing and Health Group, a research collaboration based at the Wellington School of Medicine, set out to show that, when a house is made warmer and drier, the health of occupants improves. This was done through two major studies, the first examining health improvements after retrofitting houses with insulation, the second showing that further health improvements follow if insulated houses have their heaters replaced with higher output, less polluting heaters.

Retrofitting insulation improves health

In the first study, 1,350 houses were selected from seven centres around New Zealand. Baseline data was collected the first year. In the second year, half were left as is and used as controls and the rest had insulation installed in the ceiling, foil under the floor, polythene ground cover and draught stopping around windows and doors. The control houses were provided with insulation once the study was over.

The study showed categorically that fitting insulation significantly improved occupants’ health (see Table 1). Interestingly, the average temperature increase in the retrofitted houses was only 0.6°C, so why did such a small change give rise to such a significant improvement in health? The researchers believe the reason was a change in prolonged exposure to cold temperatures. Although the average temperature change was small, the exposure to very cold temperatures (below 10°C) was significantly reduced from 3.25 hours per day to 2.26 hours per day. The control group experienced a small increase of exposure from 4.02 hours per day to 4.07 hours per day.

The retrofitted houses were also drier than the controls (see Table 1). The occupants of the retrofitted houses were subjected to relative humidities greater than 75% for 4.6 hours per day whereas the occupants of the control houses spent 6.7 hours per day at these high humidities.

Improving heating also helps

The same level of heating will result in higher temperatures in insulated homes than uninsulated houses. To receive the benefits of higher insulation, more heating can be used.

Table 1: Some findings in the Housing, insulation and health study. The retrofit group had insulation installed in the ceiling, foil under the floor, polythene ground cover and draught-stopping added around windows and doors.  
  Retrofit group Control group
Average increase in house temperature 0.6°C 0.2°C
Exposure to very cold temperatures (<10°C) 2.26 hours per day 4.07 hours per day
Average relative humidity 64.8% 66.9%
Occupants with poor health whose health had improved 40% 13%
Asthmatics ceased wheezing at night 30% 7%
Sleep at night no longer disturbed by asthma 39% 18%
Had colds or flus over the previous 3 months 58% 70%

To explore this, the group went on to see what further improvements follow when low heat output heaters are replaced with higher wattage heaters, and when unflued gas heaters (which emit significant quantities of nitrogen dioxide, carbon dioxide, carbon monoxide and water) are replaced with non-polluting heaters. The replacement heater given to the intervention group was either a heat pump, a wood pellet burner or a flued gas heater.

These houses had to have a 6–12-year-old child with doctor-diagnosed asthma, who had asthma symptoms in the previous 12 months and was living in a house in which the main form of heating was either a plug-in electric heater or an unflued gas heater.

The study examined 349 houses with 409 children in five communities. Half of the houses had their heaters replaced, with the remaining houses used as controls (the control houses were also provided with replacement heaters once the study was over).

This study showed large improvements in asthma symptoms. Children in the intervention group had fewer sick days off school, fewer visits to their GP for asthma and fewer pharmacists’ visits. They also had less reported poor health, sleep disturbance from wheezing, coughing at night and other respiratory symptoms. A statistically non-significant improvement in lung function was also found.

These studies show that it is possible to significantly improve the nation’s health if our cold damp houses are retrofitted with insulation and then well heated.

Download the PDF

More articles about these topics

Articles are correct at the time of publication but may have since become outdated.

Advertisement

Advertisement