Stuffy Wellington bedrooms could be stunting sleep and making mould

Embargoed until: Publicly released: 2026-06-26 00:01

New Zealand

Photo by Sven Brandsma on Unsplash

High CO2 levels in bedrooms at night are linked to worse sleep and functioning the next day, and increase the chance of being exposed to things like mould, bacteria and dust mites. Researchers found that half of the 20 bedrooms they surveyed in Wellington over winter exceeded the commonly recommended CO2 levels for much of the night, with some reaching very high concentrations. The researchers say this could be because most of New Zealand's housing stock is 'naturally ventilated' through windows and doors, which are commonly kept closed at night.

News release

From: New Zealand Medical Journal (NZMJ)

This study measured bedroom air quality in 20 Wellington homes and found that most bedrooms had poor overnight airflow and limited fresh air exchange. Researchers used carbon dioxide (CO2) levels as an indicator of how well stale air was being replaced with fresh air while people slept. Half of the bedrooms exceeded commonly recommended CO2 levels for much of the night, with some reaching very high concentrations. Poor airflow and lack of fresh air can allow indoor pollutants, moisture and respiratory particles to build up and may affect sleep quality, health and next-day functioning. The findings highlight overnight bedroom airflow as an overlooked aspect of healthy housing in New Zealand and suggest there may be a need for better ways to improve fresh air exchange in bedrooms.

Journal/
conference: NZMJ

Organisation/s: University of Otago, Earth Sciences New Zealand, Massey University

Funder: Building Research Association of New Zealand

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