What causes high indoor humidity levels?

High humidity levels indoors can lead to a host of moisture problems, most notably mould, mildew, pest cultivation, and other issues. Dehumidifiers are effective at managing indoor humidity levels to avoid moisture issues.

What causes high indoor humidity levels?

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High indoor humidity levels are caused by a number of different factors, including outdoor humidity, activities happening within the household, poor ventilation, and even household defects.

In this blog post, we’ll be discussing the meaning of humidity, the causes of high indoor humidity, the effects of high indoor humidity and what you can do to manage it within your home.

What is humidity?

Humidity is the amount of moisture or water vapour that is present in the air. It is usually measured in relative humidity (RH) and is used to grasp how ‘wet’ or ‘damp’ the air feels at a given time.

Humidity is an important factor that can influence our level of comfort, health, and even the environment. High humidity levels can make the air feel sticky and uncomfortable while also leading to a host of health issues that will be discussed later on.

Maintaining the right humidity levels indoors or at home is important for health and comfort.

What causes high indoor humidity?

High indoor humidity is caused by several issues, including weather, climate, indoor ventilation, leaking/plumbing issues, household activities like cooking, showering, and laundry, as well as the presence of indoor plants that release moisture into the air.

From here, we can see that there are a number of factors that contribute to high indoor humidity levels, some of which can be managed, while others, like weather and climate, are not within our control. Below is a breakdown of each factor and how it affects humidity levels in our homes.

Weather and climate

Outdoor weather conditions can have significant effects on indoor humidity levels, especially in humid climate conditions. Factors like rain, high temperatures and high outdoor humidity can lead to increased indoor humidity. Although outdoor humidity cannot be managed, we can take steps to manage indoor humidity, which will be explained below.

Poor ventilation

Poor or inadequate ventilation causes moisture from indoor sources to be trapped within the building, which leads to humidity buildup.

Not only would poor ventilation cause a buildup of humidity within a building, but it can also cause a buildup of allergens and bacteria, which, if unmanaged, can lead to sick building syndrome, a phenomenon that causes inhabitants of a building to experience allergy symptoms when residing in a building.

The use of humidifiers

Humidifiers are useful at adding humidity to environments or ambients that currently lack humidity. However, improper usage of humidifiers or using them excessively will lead to high humidity levels.

Indoor plants

Having some indoor house plants is useful and beneficial as these plants are able to act as natural air purifiers by removing toxins from the air and neutralising foul odours. However, plants also release moisture into the air through a process called transpiration. Having too many plants within a building can cause too much moisture to be released into the air, leading to high humidity issues.


How crowded an area or living space is will affect the space’s relative humidity levels as human activities like breathing and perspiring release moisture into the air.

Household activities

Tying back to the previous pointer, household activities like bathing and cooking also contribute to increased humidity, especially if these activities are accompanied by poor ventilation.

What happens when indoor humidity levels are too high?

When indoor humidity levels are too high, a host of issues, including mould, condensation, musty odours, furniture damage and pest cultivation, can occur. Maintaining optimal humidity levels will enhance your comfort, protect your home and promote better indoor air quality.

A breakdown of the effects of high humidity above can be seen in the following sections.

Mould and mildew

Mould tends to thrive in humid conditions. This is especially true for wet ceilings or walls where water leaks are likely to occur. The damage does not stop there. Mould spreads by releasing tiny spores into the air that can cause respiratory damage to those who are exposed to it. Mould also causes structural damage to your home.

Dehumidifiers remove moisture from the air and create conditions that are not conducive for mould to grow.


When warm, humid air comes into contact with cooler surfaces like glass windows, walls or ceilings, condensation is produced. Over time, moisture from condensation can cause structural damage and lead to the previously mentioned pain point, mould.

Furniture and structural damage

Excess humidity causes paint and wallpaper to peel away, and damage sensitive electronics and equipment. Damage from mould, as explained, can also cause structural damage.

Dust mites and other pests

Humid conditions are ideal for the cultivation of not just mould but also dust mites and other pests. Insects like cockroaches also enjoy humid conditions.

What are safe humidity levels?

It is recommended to keep indoor humidity levels between 30 to 60%. Humidity levels above 60% can cause the issues explained above to manifest. Low humidity levels, on the other hand, can cause other household issues such as dry skin, eye and throat dryness, dry and flaky paint, and an increase the chances of catching airborne diseases.

Dry air also exacerbates existing skin conditions, including eczema.

Our blog post Dehumidifier vs Humidity Meter, explores the different ways to measure relative humidity in your home.

How can you manage humidity?

Managing high humidity levels can be done by employing dehumidifiers, installing proper ventilation systems, using air conditioning, repairing leaks, and reducing water sources, among other methods. 

This is essential for creating a comfortable and healthy indoor environment.

Dehumidifiers for humidity control

Ionmax dehumidifiers are able to remove up to 50 litres of moisture a day with a single push of a button. They are particularly useful to clean up spills, deter the spread of mould and mitigate damages caused by flooding and other water issues.

Ionmax dehumidifiers give you the liberty of selecting your preferred humidity level and adjusting it based on real-time ambient humidity levels.

Adequate and proper ventilation

Ensure good airflow by using exhaust fans in areas that are susceptible to increased moisture, like bathrooms and kitchens. If the weather allows, open up windows and doors occasionally to improve ventilation.

Air conditioning

Air conditioners not only cool the air but also dehumidify it. Ensure that your air conditioners are well-maintained and it is set to comfortable but not excessively low temperatures. 

Repairing leaks

Inspect your home for any plumbing or roof leaks and address them promptly as they can contribute to high indoor humidity levels. Fix leaking pipes, faucets, and roof leaks to prevent moisture from accumulating.

Reducing water sources

Minimise the use of humidifiers during humid weather conditions and limit the number of indoor plants in your home if you notice signs of high indoor humidity. Regularly monitor and manage humidity levels in your home to avoid moisture issues.


High levels of humidity can lead to moisture issues like mould, condensation, furniture damage, and the cultivation of dust mites and other pests. High humidity is often caused by poor ventilation, humid outdoor climates, too many indoor plants, excessive use of humidifiers, or a combination of different factors.

There are multiple different ways to manage high humidity levels, with one of the most effective methods being the use of a dehumidifier and improving ventilation. Other methods to control humidity include using air conditioning, repairing leaks, and even reducing water sources.

Browse through Ionmax’s collection of desiccant and compressor dehumidifiers to help find the right unit to suit your needs and improve indoor air quality in your home today

Disclaimer: The information provided in this article is for general reference only. Please seek advice from professionals according to your needs.

Ionmax Australia

Ionmax Australia

Founded in 2003, Ionmax Australia has received numerous awards and accolades for its innovative products and commitment to customer satisfaction. Ionmax dehumidifiers and air purifiers have been recognised for their effectiveness in reducing indoor air pollutants and improving air quality. The company is committed to researching and developing new and improved products that meet the needs and expectations of its customers, making it a trusted name in households across Australia and beyond.

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