Children 'scientists' in world-first study looking at health and indoor climate

Pioneering new research with more than 2,000 children acting as “at-home scientists” has identified the ideal indoor temperature and humidity range for good child health and recommends changes to the Building Code.

The research is a joint project between research organisation BRANZ and the University of Auckland longitudinal study Growing Up in New Zealand.

It involved children in the Growing Up in New Zealand study collecting temperature and humidity data at home and school over two days. This new detailed indoor environment information was linked to the multiple pieces of health information collected from the children directly when they were eight years old.

The linked information showed that an indoor temperature of between 19-25°C, with a relative humidity of 50%, measured at the children’s bedtime, was associated with the best health and wellbeing outcomes.

It adds robust, child-specific data to the evidence supporting World Health Organization guidance on safe indoor temperatures (18-24°C). However, the study also found that around 60% of children lived in homes where they recorded temperatures and humidity outside of this optimal range.

Nearly half slept in a bedroom that was too cold (19°C or less) and children sleeping in these environments had a greater likelihood of reported poorer overall health, regardless of the humidity level. A further 13% slept in a bedroom that was both too warm and too humid (greater than 25°C with higher relative humidity) and they also had greater likelihood of reported poorer overall health.

Growing Up in New Zealand spokesperson Professor Susan Morton says the research is ground-breaking. “This study is the first in the world to gather actual temperature and humidity readings from the homes of thousands of children and then link the data to reported measures of child health and wellbeing.

“Most New Zealand children spend nearly three quarters of their time indoors and this study gives us a deep insight into the quality of their indoor environments across the day and night.

“Unfortunately, this research confirms that many children who live in poor quality indoor environments, where it’s too cold or too humid, do experience poorer overall health as a result,” Professor Morton says.

BRANZ General Manager of Research, Dr Chris Litten, says the link between cold and damp indoor temperatures and poorer health is clear.

Dr Litten says that the study reflects previous research which shows that children experiencing the greatest disadvantage are more likely to experience poor quality indoor environments and subsequently poorer overall general health.

“It provides important evidence to support legislation changes designed to improve the indoor environment of New Zealand buildings, such as the current energy efficiency revisions to the Building Code. Keeping buildings warm is complicated, but changes to insulation and glazing requirements, and reducing energy consumption, all contribute to the health and wellbeing of New Zealanders, ” he says.

The research project involved children in the Growing Up in New Zealand study collecting temperature and humidity data at several timepoints over two days. The children were provided with a small digital temperature and humidity gauge so they could record the indoor measurements in 2016 and 2017.

This data was then cross-referenced with National Institute of Water and Atmospheric Research (NIWA) outdoor temperature records for the same period and mother-reported data on the children’s health so that researchers could identify associations between the indoor climate and child health.

This information revealed:

• The optimal bedtime temperature under an ideal relative humidity level of 50% was determined to be between 19-25°C for good child health and wellbeing.

• Children who experienced bedtime temperatures outside this optimal temperature and humidity ranges were more likely to experience poorer general health.

• Nearly one in seven children, who experienced an indoor bedtime temperature outside of the optimal temperature and relative humidity range, had poorer overall health.

• Lower indoor temperatures tended to be associated with increased anxiety and depression symptoms in children.

Growing Up in New Zealand participant, Arya Naidu, was thrilled to be part of the 2,000 strong team of children collecting temperature data to contribute to research on New Zealand’s housing stock. She recorded temperatures at home and at school about four years ago when she was eight years old as part of a joint research project between Growing Up in New Zealand and BRANZ.

“It was fun to record the temperatures at home and at school. It was really special to be part of this research because we are helping people and contributing to something to improve our houses,” she says.