What Is Cool Biz?
In June 2005, Japan's Ministry of the Environment told the country's workforce to lose the tie. That single instruction launched Cool Biz, a government-led campaign that runs from June through September every year. The logic was straightforward: if you let workers dress for 28°C, you can set the office thermostat to 28°C and slash air conditioning demand. The campaign started as an energy-saving measure after the Kyoto Protocol, and it stuck.
June, September: Dress Code and Thermostat Settings
Cool Biz officially begins on 1 June and ends on 30 September. The thermostat stays at 28°C. Men wear short-sleeved shirts, no tie, no jacket. Women wear lighter blouses; stockings become optional. Some companies issue polo shirts or branded Cool Biz uniforms.
Not every workplace follows the same rules. Traditional banks and law firms often keep stricter dress codes. Tech companies and startups tend to go further, allowing sandals and T-shirts. If you are visiting a Yokohama office in July or August, confirm the dress expectation before you arrive.
Early-Start and Flex-Time During Summer
Some workplaces adjust their hours during Cool Biz season. They move start times earlier to avoid the hottest part of the afternoon. A common pattern: core hours shift from the standard 09:00-18:00 to 07:00-16:00 or 08:00-17:00. Workers arrive during the cooler morning and leave before the worst of the afternoon heat.
Flex-time systems let employees choose their start time within a range, typically 06:30-09:30. This makes the early-start option available without forcing everyone to arrive at 07:00. A meeting that works at 10:00 in January might start at 08:00 in summer. Confirm summer meeting times in advance.
What Is Warm Biz?
Warm Biz is the winter counterpart. It runs from November through March. The goal is to reduce heating costs by lowering thermostat settings. Offices set thermostats to 20°C or lower during heating season. That is noticeably cooler than typical winter office temperatures in Europe or North America.
The campaign encourages layered clothing: undershirts, sweaters, cardigans. Warmer fabrics like wool trousers and thicker blouses. Scarves and shawls worn indoors. Heated cushions and lap blankets at desks. Some companies provide heated vests or electric blankets as official work equipment.
Winter Thermostat Settings and Clothing
The 20°C thermostat setting is not a regulation. It is a recommendation from the Ministry of the Environment. Companies can set thermostats higher, but most participate in Warm Biz to save energy and reduce costs. In practice, workplace temperatures in Yokohama during January and February often sit at 19-21°C. That is comfortable if you are dressed for it. It is cold if you are wearing a thin shirt and expecting central heating.
Visitors from colder climates often make the wrong assumption. They think Japan is cold in winter so workplaces will be warm. The opposite is true: Japanese workplaces are cooler than many Western ones in winter because of Warm Biz.
How These Campaigns Affect Business Visitors
Summer visitors
- Bring a blazer or jacket for meetings even if your hosts wear short sleeves.
- Expect the workspace to feel warm by Western standards.
- Confirm start times before your visit.
- Carry a portable fan or cooling towel for commuting.
Winter visitors
- Bring layers: a base layer, a sweater, and a jacket.
- Do not assume the workspace will be warm enough for a single layer.
- Consider bringing indoor slippers if your feet get cold.
- Hot tea and hand warmers are common in winter workplaces.
Year-round
- Check whether your contact's workplace follows Cool Biz or Warm Biz.
- Adjust your wardrobe accordingly.
- Do not expect the thermostat to change for you.
Energy Saving and the Origins of Cool Biz
The 2005 launch of Cool Biz was part of Japan's response to the Kyoto Protocol. The country needed to cut greenhouse gas emissions by 6% from 1990 levels. Air conditioning accounted for a large share of summer energy use. The campaign was simple: let workers dress cooler so workplaces can set thermostats higher. It worked. In the first year, 46% of businesses participated. By 2007, participation reached 80%.
Warm Biz followed in 2011 after the Fukushima disaster. The country faced electricity shortages. Lowering thermostats in winter became a national priority. Today, both campaigns are standard practice in most Japanese workplaces. They are not laws. They are social norms backed by government encouragement. New employees learn about them during orientation. Foreign visitors are expected to follow them.