Value Village ／ Health
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Sleep with the air conditioner on, or off? Opinions divide around the world, and Japan's humid summers make the question pressing for anyone newly arrived. Japan's official guidance gives actual numbers.
[Verify] The figures above were confirmed through secondary sources. Before publication, check the original text of the Sleep Guide 2023 and the Ministry of the Environment heatstroke prevention information site.
Heatstroke happens indoors too. The Ministry of the Environment and the MHLW have repeatedly stressed the importance of managing room temperature, including while you sleep. Enduring the heat is the more dangerous choice.
The set temperature and the room temperature are different things. Depending on insulation and sunlight, the room can pass 29°C even with the unit set to 28°C. Check the room with a thermometer.
When humidity is high, sweat evaporates poorly, and the same temperature feels more oppressive. Aim for around 60% humidity, and watch temperature and humidity together.
A constant stream of air on the body can chill you. Simply pointing the airflow away from your body changes how it feels.
The lower limit in the guidance is 13°C. A bedroom that is too cold is not desirable, but heating dries the air, which can affect throat and skin. Think about warmth and dryness at the same time.
Comfort varies with age and build. Even in a shared room, adjusting individually with bedding is more realistic.
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https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/kenkou/suimin/index.html
https://www.wbgt.env.go.jp/
https://www.mhlw.go.jp/seisakunitsuite/bunya/kenkou_iryou/kenkou/nettyuu/
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.
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