Heating a Tokyo apartment without trapping damp

When you arrive at a Tokyo apartment in winter, ask how the bedroom, living area and bathroom are heated. The arrangements vary by unit, so a working air conditioner in one room doesn't tell you what to expect in the others.

Find the ventilation controls too, and ask which should stay on. You’ll want the room warm without letting damp build up. The heating setting alone may not do both jobs.

Check what the bathroom fan is designed to do

Panasonic’s bathroom fans show why the model matters. The FY-13UG7E can warm the bathroom before you use it, ventilate it, dry the room and dry clothes. Panasonic recommends leaving its 24-hour ventilation running. The FY-24UW5 ventilates only the room where it’s fitted. Two ceiling fans can look alike but do different jobs.

Check the model number before choosing a setting. If yours has 24-hour ventilation, leave that running as instructed even when a timed drying cycle has finished. If the fan only ventilates the bathroom, you may still need other fans or vents elsewhere. Ask the rental company which controls affect the bathroom and which affect the rest of the apartment.

Find heating mode before changing the temperature

Look for 暖房 (danbō, heating) on the air-conditioning remote. 冷房 (reibō) means cooling and 送風 (sōfū) means fan operation. Use the model's instructions rather than relying on a familiar-looking sun or snowflake icon.

Start with a comfortable setting and allow the appliance to operate as instructed. Check the temperature where you sit or sleep; a setting on the remote doesn't prove the whole room has reached it. Keep the intake and outlet clear, and ask the rental company before moving heavy furniture or adding seals around windows.

An air conditioner can pause heating to remove frost from its outdoor unit. Daikin's winter guidance explains that warm airflow can stop while frost is removed, then resume. The exact behaviour depends on the model and conditions. If it doesn't resume as the manual describes, displays an error or cannot keep the room comfortable, report it rather than assuming every pause is normal.

Send the model number, the setting you’ve chosen and a photo of any error message. Explain when the problem happens and whether it affects one room or the whole apartment. Don’t open the appliance or try to repair it yourself.

Keep ventilation operating as instructed

Locate 換気 (kanki, ventilation) and any 24時間換気 (nijūyo-jikan kanki, 24-hour ventilation) control. Ask which switches operate the bathroom fan, whole-apartment ventilation and any bathroom heating or clothes-drying function; they may be separate modes on one panel.

Use the building's instructions after showers and cooking. Don't block a vent because the air feels cool, and don't assume the room air conditioner brings in fresh outdoor air. If a vent is noisy, obstructed or apparently not working, ask for it to be checked.

During a cold spell, opening a window briefly may be more comfortable than leaving it open for hours. What works depends on the building and weather, so ask the rental company how to air out this apartment.

Notice where condensation returns

Wipe condensation from windows you can reach safely, using the cleaning method recommended for them. Keep damp towels and clothes out of closed cupboards. Check inside wardrobes and behind furniture you can reach, but don’t drag heavy furniture across the floor.

If the same patch gets wet again, tell the rental company where it is and when it happens. Take a photo before wiping it, and mention recent showers, laundry and which fans or vents were on. Damp isn’t always caused by how you use the room; the company may need to check for leaks, building problems or a faulty fan.

Leave space for air to move around stored items, and dry clothes fully before putting them away. For a futon, ask about the supplied airer and bedding-care instructions. Don't hang bedding over a balcony rail unless the building permits it and it can be done safely.

The rainy-season guide has more on managing persistent humidity, while the laundry guide covers drying equipment and controls.

Don't use a mould cleaner on every damp surface

If you see mould, take a photo and contact the rental company before treating walls, bedding or furniture. Ask them to check what’s causing it and tell you how it should be cleaned. If it keeps coming back or covers a large area, a stronger spray alone won’t solve the problem.

Check the exact product label and approved surfaces. Kabi Killer's manufacturer, for example, says its product isn't suitable for fabrics. A bathroom mould remover isn't a general treatment for curtains, a mattress or a leather bag.

If the company asks you to clean a surface and the product is safe to use on it, follow that cleaner’s label. Check how to ventilate the room, what gloves or other protection to wear, how much cleaner to use, how long to leave it on and whether to rinse or wipe afterward. Never mix cleaning products.

Ask before adding a heater

Try the heating supplied with the apartment first. If it doesn’t warm the room enough, tell the rental company. Before adding a heater, ask whether it’s allowed and where you can safely put it and plug it in.

For a portable electric heater or a supplied kotatsu, follow the actual manual, keeping bedding, clothing and cords arranged as directed. Don't use a heating appliance to dry laundry unless it is explicitly designed for that use.

A fuel-burning heater has different safety requirements from an electric appliance. Don't buy or light one based on an assumption that an older building allows it; get the building's approval and appliance instructions first. If the supplied heating isn't adequate, ask the rental company to resolve that rather than experimenting with another fuel source.

Understand how heating is billed

Check whether electricity is metered, included or subject to an allowance. Ask how any extra usage is calculated and where to see the relevant meter or bill. The utility-fee guide explains the questions to ask about an inclusive charge.

For an illustrative calculation, an appliance drawing a steady 1 kW for four hours uses 4 kWh. Multiply 4 kWh by the price per kWh on your bill. Your bill may also include a monthly charge and other adjustments listed by your electricity company. The amount of electricity a heat pump uses changes while it runs, so it won't always use the maximum amount shown on its label.

As you look for ways to lower the bill, keep the room warm enough and leave the ventilation running as instructed. If it still stays cold or damp, send the rental company photos and a description of the problem, and ask when someone can check it.