Problem Statement:
With the rainy season and summer approaching, when humidity in Kansai and Osaka soars, the risk of hidden damage to wood and natural materials and mold growth is increasing in luxury homes and villas. Deterioration of unseen areas can seriously affect property values.
What you will learn from reading the article:
In this article, you will learn about the rainy season trends for 2025, moisture risks unique to luxury homes, the MIST Method® for mold prevention without damaging materials, the mechanism of the continuous anti-mold treatment, and structural measures through equipment and renovation.
Benefits of reading the article:
You will not only prevent moisture-induced home deterioration and protect property values, but also clarify what safe and secure mold remediation measures are best suited for high-net-worth homes. You will also get an action plan that you can quickly implement.
1. Pre-Seasonal Rainy Season Humidity Trends in Osaka/Kansai and Forecast for 2025
In the Kansai and Osaka areas, the rainy season usually begins in late May or early June. 2025 is no exception, with the Japan Meteorological Agency forecasting that the rainy season will begin somewhat earlier than usual. During this time of year, humidity rises sharply, creating a hot and humid environment that can cause moisture to accumulate inside homes at once. Especially in luxury houses and villas, spaces with inadequate ventilation and the use of many natural materials make it easy for the effects of moisture to lead to long-term damage.
1-1. Timing and Characteristics of the Onset of the Rainy Season in 2025 (Kansai, Kinki)
The onset of the rainy season in the Kinki region in 2025 is predicted to be around June 2 to June 10, according to the long-term forecast by the Japan Meteorological Agency. The rainy season tends to be on par with the average year or slightly earlier, especially from late May onward, when humidity quickly increases and, together with temperatures, creates a gloomy environment. This year, the Pacific High is forecast to be stronger, so humid conditions may persist for a long period of time. In such weather, it will be difficult to open windows for ventilation, and humidity will tend to stay indoors.
Many rooms in luxury homes, condominiums, and vacation homes have infrequent or unused air conditioners, and these spaces are especially prone to moisture accumulation. In addition, heavy rains are expected in parts of the rainy season in 2025, and attention should be paid to moisture intrusion due to condensation and leaks caused by the sudden rise in humidity.
1-2. Humidity Risk from Short-term Trend of Rainy Season and Fast Rainy Season
Due to recent climate change, the duration of the rainy season has been shortened and the so-called “short-term intensive rainy season” is taking hold. It is predicted that a similar trend will be observed in 2025, increasing the risk of significant moisture damage to housing due to the large amount of moisture flowing into buildings in a short period of time.
Particularly problematic is the increased frequency of condensation, which occurs as a result of high temperatures that continue without any time for humidity to drop. Condensation tends to occur in places that are difficult to see, such as the backs of closets, behind walls, and behind furniture, and many cases of mold growth without being aware of it have been reported. With the climate changing in a short period of time, moisture management in housing is becoming an even more important issue than before.
2. Deterioration Risk Caused by Moisture in Luxury Housing
Many natural materials are used in luxury housing, such as natural wood, plaster, solid wood flooring, and diatomaceous earth. While these materials are beautiful to look at and have excellent humidity control properties, they are very susceptible to moisture. In a high-humidity environment during the rainy season and summer, building materials are prone to a variety of problems, such as repeated expansion and contraction, and mold formation in unseen places. In particular, the loss of humidity control function and mold growth in hidden areas can be a major cause of overall housing property value decline.
2-1. Damage to Wood and Natural Materials and Risk of Hidden Mold
Among natural materials, wood is particularly sensitive to moisture, and if the humidity exceeds a certain level, the moisture content increases, causing expansion, warping, and cracking. In addition, moisture penetrates not only the wood surface but also into the interior, increasing the risk of mold growth in unseen areas. In particular, the detection of mold tends to be delayed in hard-to-see areas such as under floors, behind ceilings, and in walls, where ventilation is poor and conditions are conducive to mold growth.
Over time, this “hidden mold” can even adversely affect structural parts, resulting in a shortened lifespan for the building. In many cases, even if the building is kept looking beautiful on the outside, people are unaware that the mold is progressing inside, and by the time they realize it, the condition is difficult to repair. Regular inspections and early action are essential.
2-2. Structure and Condensation Risk Specific to Luxury Houses
Many luxury houses have large windows, vaulted ceilings, and open floor plans that emphasize the design of the exterior and interior. While these structures create spatial beauty, they also tend to create “dead space” where airflow is blocked and moisture tends to accumulate. In addition, large openings tend to have a large temperature difference from the outside air, making condensation more likely to occur.
In particular, condensation can occur not only on glass windows, but also inside walls and behind insulation. This allows moisture to be trapped for long periods of time, creating a breeding ground for mold and corrosion. In high-end housing, it is important to have a good insulation performance and ventilation plan from the design stage, and even after living in the house, frequent air circulation and humidity control are required. 3.
3. Basic Line of Effective Mold Prevention during the Rainy Season and Summer
During the rainy season and summer months, when humidity and temperatures rise, mold is more likely to occur in all indoor areas. This is especially true in luxury homes and vacation homes, where many rooms are not used on a daily basis, and the tendency for moisture to accumulate due to air stagnation can cause mold. The three basic principles are: do not allow moisture to accumulate, improve ventilation, and leave no food for mold. Specific methods to achieve this are introduced below.
3-1. Ventilation, Dehumidifier, and Air Conditioner Utilization
First, regular ventilation is essential to reduce the humidity that causes mold. Although some high-end houses may have 24-hour ventilation systems, it is important to check the operation mode and clean the filters regularly. It is especially important to consciously open windows or use a circulator to move air in rooms that are used infrequently.
Dehumidifiers are one of the most reliable devices during the rainy season and summer months. Regular operation is especially effective in closets, bathrooms, and basements, where humidity tends to rise. Recently, there are models that simultaneously dehumidify and clean the air, as well as more powerful models for drying clothes, so it is recommended to use different types. Air conditioners can also be effective by using the “dehumidification (dry) mode,” which controls humidity while maintaining a comfortable room temperature by setting the temperature at around 28 degrees Celsius. 3-2.
3-2. Preventive Cleaning Points by Mold-Prone Areas
Mold-prone areas include bathrooms, kitchens, washrooms, closets, under beds, behind furniture, and closets. These areas are prone to moisture and to the accumulation of sebum and dust, which are sources of nutrients for mold, and therefore require intensive cleaning.
In the bathroom, make it a habit to wipe the walls and floor with a towel after bathing, and run the exhaust fan for at least 30 minutes after bathing to expel moisture. In the kitchen, attention should be paid to grease in the storage space under the sink and around the exhaust fan. In bathrooms, ventilation under the washing machine and wiping the floor dry after use will help. In closets and closets, use humidity regulators and sunken boards to create air flow to prevent moisture buildup.
It is also important to regularly shift the position of furniture to allow air to flow between the furniture and the walls, and to ventilate unseen areas. By thoroughly following these basics, mold growth can be greatly reduced.
4. Introduction of the MIST method that does not damage materials for wealthy people
High-quality materials are often used for interiors and building materials in luxury houses, and ordinary mold removal methods often damage the surfaces. The MIST method has been attracting attention for its ability to remove mold without damaging the materials. This method uses a chemical agent that is atomized and permeates the mold to reach the mold deep inside, where it cannot be seen, and removes the mold from its root cause. It is the best option for preserving the beauty and health of your home.
4-1. What is the MIST Method? Differences from other companies’ methods
The MIST method is a unique method of removing mold using a special chemical that is gentle to the material. The most common methods of mold removal are scrubbing with a brush or bleaching with strong chemicals, but these methods have the risk of scraping or discoloring the material. In contrast, the MIST method adjusts the ingredients and concentration of chemicals according to the mold growth and characteristics of the material, and sprays the chemicals in the form of a mist to safely treat even the most delicate materials.
The MIST method is also effective for mold that is hidden in areas that cannot be seen or deep within the material because of the high penetration power of the chemicals. It can approach the roots of the mold, which cannot be removed by other companies’ methods, and thus greatly contributes to the prevention of recurrence.
4-2. Consideration and Examples for Wood, Natural Materials, and Historical Buildings
The MIST method is best suited for buildings with natural materials such as wood, solid wood, diatomaceous earth, and plaster. Especially for buildings that are difficult to restore, such as historical buildings and cultural properties, preservation of the materials is very important, and therefore, the MIST method, which can remove the materials without damaging them, is highly valued.
In fact, the MIST method has been used in the renovation of cultural facilities, shrines and temples, and old private homes, proving that it is possible to remove mold without damaging the original texture and value of the materials. This method is the only option that is both safe and reliable, even in general housing, especially when high-end building materials are used. 5.
5. The mechanism of sustained mold remediation that is safe even after removal
Simply removing the mold does not prevent it from reoccurring. The MIST method uses a mold inhibitor to protect the material after removal, coating it with a mold inhibitor to prevent mold from re-growing over the long term. This allows the material to remain clean even in humid environments.
5-1. Deep penetration of the material and effect of the fog-like agent
In the MIST method, after mold removal, a special anti-mold agent is sprayed onto the work surface in the form of a mist. Because the particles of this mist-like agent are extremely fine, it penetrates deep into the material and completely decomposes and removes mold spores and mycelium that are lurking there. In addition, this anti-mold agent forms a thin protective film on the surface even after drying, preventing the entry and establishment of mold fungi from the outside.
This effect protects materials from mold for a long period of time, even during the rainy season and summer months when humidity tends to be high. It is also effective in dealing with hidden mold, especially since the agent can reach inaccessible areas such as under ceilings, under floors, and behind walls.
5-2. Long-Term Recurrence Prevention Strategy with Mold Remedies
The mold remedies used in the MIST method are not only effective immediately, but also have excellent long-term sustainability. Since it remains effective for six months to a year after installation, it is particularly suitable for areas where mold recurs frequently and where humidity is chronically high. In addition, the chemical is composed of ingredients that have minimal impact on the human body, making it safe to use even in homes with small children or the elderly.
Furthermore, the protective film created by the agent does not impair surface air permeability, allowing the humidity control function of the material to remain intact. This makes it possible to achieve both a comfortable and hygienic environment for the home, leading to long-term preservation of the home.
6. Approach for villas and luxury condominiums
Because villas and luxury condominiums are not occupied on a daily basis for long periods of time and have little air flow, humidity tends to accumulate easily. Especially in areas such as the Kansai region, where high humidity persists from the rainy season through the summer, moisture can unknowingly penetrate into the interior of building materials, causing mold and deterioration. Below are some effective countermeasures for such properties.
6-1. Moisture Problems and Ventilation Measures in Low-Use Areas
In rooms that are not used for long periods of time, air tends to stagnate and moisture tends to accumulate. Therefore, it is important to set up a system to create regular air flow by installing an exhaust fan with a timer or a dehumidifier that operates automatically. IoT-based management is also effective, for example, by linking to smart appliances to check humidity conditions and control automatic operation even when you are away from home.
In storage spaces, humidity regulators and diatomaceous earth mats should be installed to reduce the rise in humidity. In addition, creating space under stored items by using sunken boards or ventilation panels will prevent moisture retention. 6-2.
6-2. How to use dehumidifiers, humidity control materials, and insulating building materials
It is desirable to choose a dehumidifier with high performance and wide coverage, and it is important to select a product that matches the installation location. For example, a small quiet type for a small closet, a hybrid type for a large living room, and so on.
Humidity control materials include charcoal, diatomaceous earth boards, and silica gel sheets, which are natural materials with high moisture absorption performance and can be used repeatedly. In addition, by improving the insulation performance of buildings, temperature differences between indoor and outdoor areas can be reduced, thereby curbing dew condensation and humidity increases. Renovating insulation and installing insulated glass are very effective long-term measures.
7. How to Prevent Moisture through Structural Measures and Remodeling
In order to prevent moisture and mold from occurring at the root, it is effective to implement measures in the structure of the home itself, in addition to reviewing lifestyle habits and installing appliances. This is especially true for luxury homes, which require remodeling and architectural design that incorporates functional moisture countermeasures while maintaining both aesthetics and comfort. Here are some measures that can be taken structurally, including windows, walls, ventilation equipment, and interior building materials.
7-1. Facility Renovation of Windows, Walls, Insulation, Total Heat Exchange Ventilation, etc.
Large windows enhance the appearance and let in light, but at the same time, the temperature difference with the outside air can cause condensation. Changing to double-glazing or plastic sashes with high thermal insulation performance can reduce the temperature difference between inside and outside and prevent condensation. In addition, simply installing additional insulation around windows can also be effective in preventing moisture.
Reinstalling insulation inside the walls and using materials with a humidity control function along with insulation can improve the moisture balance of the entire structure. Furthermore, by installing a total heat exchange ventilation system, humidity can be controlled while the indoor air is exchanged for fresh air, making the living environment even more comfortable.
7-2. Use of humidity-controlling building materials (diatomaceous earth, plaster, etc.) and mold-resistant building materials
In recent years, the introduction of interior building materials with humidity control properties has been attracting attention. Diatomaceous earth and plaster are typical examples. These are natural materials with high moisture absorption and desorption properties, and are effective in stabilizing indoor humidity. They are also excellent in design and can be incorporated into the interior of high-end homes without any sense of incongruity.
In addition, wallpapers, paints, and floor coverings with anti-mold agents kneaded into them are also available on the market, and by choosing these products, you can prevent the occurrence of invisible mold. Especially for the interior walls of water closets, closets, and closets, these building materials can provide long-term peace of mind.
8. 5 items to prepare for a short rainy season and hot and humid summer
Due to climate change, the “fast rainy season,” in which the rainy season falls intensively in a short period of time, has been increasing in recent years. After the rainy season ends, it becomes hot and humid at once, rapidly creating an environment conducive to mold growth. The first step to prevent mold growth is to prepare for this period by taking the following five precautionary steps at home.
8-1. Preparation for Cleaning, Drying Bedding, and Laundry before the Rainy Season
Before the rainy season, look around the entire house and clean it. It is especially important to thoroughly remove mold and dirt from places where moisture tends to accumulate, such as behind furniture, closets, curtains, and window frames. Dry futons and mattresses thoroughly in the sun to remove moisture, and be prepared by installing desiccants and humidity-controlling products in closets as well.
When drying laundry indoors, use a dehumidifier and fan to dry it in as short a time as possible. If the laundry remains damp for a long period of time, the humidity in the room will increase, which can lead to mold growth.
8-2. Action plan for heavy rain and rising humidity line
If humidity rises all at once due to heavy rain or typhoons, leaks and flooding under the floor may occur. Check points of rainwater intrusion from the outside in advance, such as roofs, exterior walls, and seals around windows, and repair them as soon as possible if deterioration is found.
Also, install a hygrometer and reinforce ventilation and dehumidification when indoor humidity exceeds 60%. By sharing information about moisture management with family members on a daily basis and determining their roles, you will be able to respond quickly in case of emergency.
9. Early detection and periodic inspection system recommended by experts
Deterioration caused by mold and moisture is often not addressed until it has reached a visible stage, and the damage tends to be more serious. That is why early detection through periodic inspections and humidity control is extremely important. By introducing professional diagnosis and regular maintenance, signs of mold can be detected in the early stages and addressed at the root cause.
9-1. How to Introduce Humidity Monitoring and Spot Inspections
By utilizing a home hygrometer or smart temperature and humidity sensor, the indoor environment can be checked on a daily basis. With a high-performance device, it is possible to install them in multiple rooms and manage them all together with an application. Another method is to use mold inspection kits in unseen areas such as behind walls and under floors as spot inspections.
By conducting these monitoring on a regular basis, you will be able to notice earlier when humidity is high or when moisture is accumulating in certain areas, and you will be able to take preventive measures.
9-2. The Importance of Regular Professional Inspections and After-Sales Support
To further ensure the health of the house, it is essential to introduce regular inspections by a professional contractor. By inspecting the entire house with professional eyes, it is possible to identify areas that are often overlooked and the causes of abnormal humidity, and to take appropriate measures.
Particularly in high-end homes, a systematic set of inspections and maintenance is recommended to preserve long-term value. Some contractors offer periodic mold prevention installation as aftercare support after mold removal, enabling sustainable measures to be taken.
Mold removal and mold remediation is available at Mold Busters Osaka and Mold Remodeling Tokyo and Nagoya
If you are troubled by the high humidity environment in Kansai, especially with mold problems that become more serious from the rainy season to summer, please contact “Mold Busters Osaka”. In addition, if you live in the Tokyo metropolitan area or the Chubu area, “Mold Removal Reform Tokyo” and “Mold Removal Reform Nagoya” can help you. We use our proprietary MIST method, which uproots and removes mold without damaging the material, to prevent the reoccurrence of mold and to safely install the work without damaging the aesthetics.
The MIST method used by Moldbusters is an excellent mold removal technique that does not scrub or cut and does not damage the material. The concentration of the special agent is adjusted according to the condition of the material and the growth of mold, and the agent is applied in the form of a mist to decompose and kill the mold to the depths that cannot be seen. In addition, the use of human- and environment-friendly ingredients makes it safe to use even for households with small children and the elderly. After sterilization, a highly sustainable anti-mold treatment is applied to suppress the risk of reoccurrence over the long term.
Furthermore, Taikoh Kenso Co., Ltd. is ready to handle remodeling at the same time as mold removal. Not only can we beautifully repair walls, ceilings, and floors that have deteriorated due to mold damage through remodeling, but we can also take comprehensive measures to prevent recurrence in the future by incorporating building materials with anti-mold specifications and materials with humidity control properties. When remodeling, we take full responsibility for everything from interior design proposals to construction and after-sales maintenance.
Our remodeling projects specifically address the following requests
Interior remodeling to prevent recurrence of mold (wallpaper replacement, diatomaceous earth or plaster finish, etc.)
Preventing condensation by introducing humidity-regulating materials and heat insulators
Remodeling of water areas (bathrooms, washrooms, kitchens, etc.) to prevent moisture
Installation of window sashes and equipment to improve insulation and ventilation
Interior plans that combine design and functionality for luxury homes and villas
If mold removal and remodeling are done by separate contractors, it is easy to have issues with scheduling and consistency of workmanship, but with Taiko-Kenso, Inc. To protect the value and comfort of your home, please leave it to the experts.
Please feel free to contact us at “Mold Busters Osaka” in Kansai, or “Mold Removal Reform Tokyo” and “Mold Removal Reform Nagoya” in Kanto and Chubu. We will protect your precious home.
