Created for expats living in Japan

Fighting Humidity and Mold During Japan’s Rainy Season

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Summer in Japan can be an exciting time, full of bright summer festivals, fun beach trips, and shaved ice in myriad flavors. However, summer is also a time of high humidity, long sticky days, and mold. Fighting mold in the home is a constant exercise for many who live in Japan. Fortunately, there are a range of measures you can take to try and keep the mold at bay.

Japan’s Humid Climate

Despite Japan being a small country geographically, there is a large range of climates from the cooler areas of Hokkaido to the tropical weather of Okinawa. One consistent aspect through all these variations is the high level of humidity.

Summer is also when the “rainy season” or tsuyu (梅雨) arrives, further contributing to the humidity. The rainy season generally hits around June or July and results in a few weeks of very wet weather and near-constant rain. After the rainy season is when summer truly kicks in with constant high temperatures and high humidity. The temperature often sits around 30–35˚C in summer, but with humidity at around 75–85 percent, it can feel much hotter.

High-humidity climates can be a difficult adjustment for those coming from areas with a generally low humidity. The air feels heavy and thick, and the moisture in the air inhibits the body’s natural ability to evaporate sweat and cool down, which can lead to dehydration and heat stroke. Every summer in Japan, there are many news reports of people being taken to the hospital due to heat-related issues.

Humidity can also increase the growth of mold in the home and affect everything from clothes, to furniture, to personal belongings. It is important to be aware of these issues when living in Japan and take action to prevent and combat the problems associated with high humidity.

Where to Look for Mold in Your Home

When looking to address humidity-related issues in the home, the first step is to identify the issues and the causes. One of the main things to look at is where the humidity, mold, and moisture are coming from.

Some of the main areas to focus on in the home are places where moisture is naturally going to accumulate. The obvious culprit is, of course, the bathroom. As a room that is regularly wet, the bathroom is prone to mold growth. Kitchen sinks also fall into the same category. Windows are a perhaps unlikely, but regular area of mold growth. As the barrier between the humid outside and the hopefully drier inside, it is common for condensation to accumulate there, which can then lead to mold. Enclosed spaces are also a key concern. These include closets, shoe cupboards/boxes, and general storage areas.

How to Prevent Moisture in Your Home

There are a number of measures that can be taken to prevent mold from growing during the summer months in Japan. The first of these is ventilation. While it may feel counterproductive to open windows and let the humid summer air in, this movement of air is actually useful in keeping the air in your house from becoming stale and stagnant. As mentioned above, windows, bathrooms, and sinks are common areas for mold to grow. One way to avoid this is to keep them as dry as possible. This means regularly wiping the windows and window frames of condensation, wiping the bathroom down after showering, and wiping the sinks after use.

Of course, the main focus of preventing mold is to dehumidify the house. There are a number of methods that can be used to achieve this. The first is keeping the ventilation fan in the bathroom on at all times. Japanese bathroom fans are made to be left on, so it doesn’t cause any fire or electrical hazard to run it 24/7. This helps with ventilation and keeping the bathroom dry.

The second is running the air conditioner on the general cooling function, which helps dehumidify the house. However, there is usually also a “dry” setting that is designed to focus predominantly on dehumidifying. To take dehumidifying up a notch, there are a range of dehumidifier machines available on the market. These can use a lot of electricity, but they provide a huge difference in keeping the house free of mold.

However, dehumidifiers can be quite expensive, so there are a range of budget-friendly options available. These include passive moisture absorbing pads to be placed on the shelves of shoe cupboards and drying “boxes” that can be placed in rooms to slowly absorb moisture from the air until they are full of water. A great option for closets and small storage spaces is moisture absorbing packs. These are sometimes the same as silica gel packets that regularly come with new shoes or bags, or sometimes a different material but of similar size and shape. The small size allows them to conveniently fit in drawers and cupboards.

Fighting Mold in Your Home

There are a range of products available in Japan to get rid of mold. One of the most popular products is called “Kabi Killer.” Kabi means mold in Japanese, so most products with “kabi” in the title are designed to help with controlling or killing mold; this particular product has gained cult status as the ultimate in getting rid of mold. There are different varieties for different surfaces, so it is important to check before buying. It is also important to keep the area ventilated while using products like this as there are often strong chemicals involved.

Some people prefer to use more natural solutions to remove mold. These usually involve distilled white vinegar and/or baking soda, both of which are easily available in Japan. Regardless of whether you are preparing for the summer season or trying to repair the damage wreaked by humidity, there is no doubt you will find solutions available in Japan.

Stay Cool and Safe from Japan’s Summer Heat

Summer in Japan can be a time of great excitement. However, the season also brings the high temperature and humidity of the rainy season along with mold. Avoiding mold can seem like an everlasting task, but with a few simple steps taken regularly, it can become an easy part of your everyday routine. For more information on surviving the summer heat in Japan, read our guides on air-conditioning remote.

Dehumidifier Machines and Useful Tools

You can purchase dehumidifier machines, moisture absorbers, moisture absorbers for windows online.