Tokyo and most other cities in Japan have high humidity, which causes to promote mold growth. The mold can grow not only during the rainy season but also in environments where condensation occurs, with temperature differences between indoor and outdoor settings. In rental housing, mold growth can cause problems when you move out. So, let's find out how to cope with condensation effectively to prevent annoying mold.
Why does condensation occur? When and where?
Condensation, or Ketsuro (結露), is the process of water vapor turning back into liquid water. Condensation occurs when the temperature dramatically drops and diminishes its capacity to hold water vapor. On a hot summer day, if you pour cold brown tea into a glass, you will notice water droplets forming on the surface. This is an example of condensation.
In housings, condensation occurs when the temperature difference between the inside and outside of the house becomes large. In the cold winter, condensation happens while warming up rooms inside, with higher temperatures than outdoors. During summer, the use of air conditioners forms condensation by bringing humid outside air into the room, resulting in temperature differences between the inside and outside.
The condensation often occurs around stuffy, damp places in unventilated rooms with large temperature differences inside and outside. Window glass is particularly susceptible to condensation because it is in contact with warm air from inside the room and cold air from outside, creating a significant temperature difference. Furthermore, caution is advised regarding condensation in areas like behind furniture and the backs of closets and cupboards, where air tends to stagnate and where temperature differences are likely to occur.
Air conditioners may cause condensation due to their usage
Condensation problems often occur in winter, but they can also occur during summer if the air conditioner is used continuously at low-temperature settings. This is common in apartments. If you leave the air conditioner on at a low temperature, the pipes connecting to the AC compressor can become too cold, resulting in condensation due to water droplets. In some apartments, the air conditioner and the AC compressor are separated, with the connecting pipe running through the room.
Condensation causes mold growth
Mold grows in environments with temperatures of around 20°C and humidity of over 60%. When humidity rises to 80%, mold growth increases significantly. The main cause of high humidity indoors is definitely condensation, which leads to mold growth.
Removing mold is no picnic
When mold first appears, it can be removed relatively easily with a neutral detergent. However, you can hardly remove the mold kept left for a while. In particular, black mold usually leaves stains and dirt, barely removed by scrubbing with a brush using a special detergent. Depending on the material and location, such as wallpaper in the corner of a room or the walls of a Japanese-style room, it may only be possible to remove with the help of a professional.
In rental housing, mold caused by condensation can lead to issues with compensation
If mold appears in a rented room, it is essential to promptly notify the management company about it and request an inspection. This step is crucial because it is difficult to determine whether the tenant or structural issues caused the mold in the building. If the tenant does not notify them, there is a high possibility that compensation for damages will be required when moving out.
Prevent condensation to get mold-free
Keeping rooms clean and maintaining humidity low is important while black mold feeds on damp dust and dirt. Therefore, reducing condensation is crucial to discourage mold growth.
How to prevent condensation
1. Let in fresh air and get air circulation
Using a ventilation system will help remove water vapor from the room. Using a circulator placed near windows will also help with dehumidification. The key is to avoid creating a temperature or humidity difference between the room inside and outside. Open windows sometimes and let in fresh air to keep rooms from getting stuffy. The room you rarely use also needs fresh air by opening windows and drapes.
In closets and storage spaces, make sure there is air circulation. If you pack too many items inside, it will become stuffy, and moisture may accumulate at the bottom. To improve airflow and reduce temperature differences, lay down a wooden slat (Sunoko すのこ) on the floor or occasionally open the door.
2. Place furniture at least 5 cm from the wall
The 5 cm distance will allow air to flow behind the furniture. Avoid placing furniture that is prone to condensation on the side of exterior walls.
3. keep the room temperature around 20°C
Adequate temperature reduces the temperature difference between inside and outside, which helps prevent condensation.
4. Use a dehumidifier
During the rainy season and on rainy days, using a ventilation fan is ineffective because it draws in humid air from outside. Instead, use a dehumidifier.
5. Install window heaters to prevent condensation.
Use the heater for windows during the cold winter months. Place them at the bottom of the window to prevent condensation by keeping the temperature from dropping.
6. Use electrical room heaters
Paraffin heaters and stoves release water vapor when burned, which can increase room humidity. Consider using air conditioners, halogen heaters or other electric heaters that do not produce humidity.
7. In houses with shutters, close them at night.
On winter mornings, condensation often forms as the outside air cools overnight. Closing the shutters increases the air layer between the shutters and the windows, which can help reduce condensation.
8. Use condensation-proof products
Various condensation-proof products are available from DIY stores and 100-yen shops. Using them alongside proper room ventilation is a good option.
- Condensation-proof spray (結露防止スプレー Ketsuro-boushi spray)
Spraying it on window glass prevents condensation from turning into water droplets.
- Disposable dehumidifier (除湿剤 Joshitsu-zai)
A dehumidifier box gathers moisture in enclosed spaces. If left in a closet or other damp place, the moisture condenses into water and accumulates in the box.
- Applying an anti-condensation film to window glass (結露防止シート Ketsuro-boushi sheet)
Apply the film directly to the window to prevent condensation from forming.
Caution!
Anti-condensation films cannot be applied on wired glass windows due to the risk of cracking. Even if the windows have non-wired glass, those living in a rental house need to consider the restoration required when moving out.
If condensation occurs on the window
If condensation occurs, wipe off the water droplets as soon as you find them. The window left wet for a long time raises the humidity in the room. Indeed, wiping off condensation can be a chore. Preventing condensation is better than dealing with it after it forms.
