“Optimal Humidity”: Why 40–60% Is the Golden Rule and How to Maintain It at Home

Have you ever noticed that in some homes the air feels fresh and easy to breathe, while in others it feels heavy and stuffy? In most cases, the issue is not the temperature, but the level of indoor humidity.

Both air that is too dry and excess humidity indoors can have a direct impact on your wellbeing, sleep quality and even your health. This is why more and more people are asking: what should the humidity level in a home actually be?

Scientific studies show that the ideal indoor humidity level is between 40–60%. This range is considered the “golden rule”, because these conditions are the most comfortable for the human body and create an environment that is less favourable for viruses, bacteria and mould.

What Is Optimal Humidity and Why Is It So Important?

Optimal indoor humidity refers to the moisture level at which the human body feels comfortable, while the environment becomes less suitable for the growth of bacteria, viruses and mould.

According to the World Health Organisation and various scientific studies:

• When humidity drops below 30%, mucous membranes begin to dry out and respiratory irritation increases
• When humidity rises above 60%, conditions become favourable for mould and dust mites
• Within the 40–60% range, the survival rate of airborne viruses decreases

This is why maintaining proper humidity levels is directly linked to your health and overall wellbeing.

What Happens When the Air Is Too Dry?

Excessively dry indoor air is most common during the colder months, although it can continue into spring.

Common effects of dry air:

• Dry skin, eyes and lips
• Sore throat and difficulty breathing
• Poorer sleep quality
• More frequent colds
• Constant discomfort

This happens because dry air irritates and dries out the mucous membranes in the respiratory tract — one of the body’s natural defences against viruses.

How to Solve It

• Use a humidifier, especially during winter
• Monitor humidity levels with a hygrometer
• Use an enthalpy MVHR system, which helps retain some moisture
• Ensure your ventilation system is functioning properly

What Happens When the Air Is Too Humid?

Excess humidity indoors can often be even more harmful than dry air.

The main problems include:

• Mould growth
• Increased dust mite activity
• Heavy, “sticky” air
• Lingering unpleasant odours
• Greater risk of allergies and respiratory issues

Over time, excess humidity can affect not only your health, but also walls, furniture and the structure of your home itself.

How to Solve It

• Ensure continuous air exchange
• Use an MVHR system
• Use a dehumidifier if necessary
• Reduce indoor moisture sources (such as drying laundry indoors)
• Replace MVHR filters on time

How Does an MVHR System Help Maintain Optimal Humidity?

A properly functioning MVHR system helps maintain balance indoors by:

• Removing excess moisture from bathrooms and kitchens
• Ensuring continuous air exchange
• Reducing the risk of condensation and mould

Some modern systems – particularly those with an enthalpy heat exchanger – can even help retain part of the indoor humidity during winter, preventing the air from becoming too dry.

However, there is one important condition:

👉 All of this only works properly when MVHR filters are clean.

Why Is Filter Replacement Directly Linked to Humidity?

Contaminated MVHR filters reduce airflow. This means moisture is removed less effectively, while CO₂ levels, unpleasant odours and mould risk begin to increase.

In practice, it looks simple: the system is running, but the effect is minimal.

This is why filter replacement is not only about clean air – it is also about maintaining a healthy indoor climate.

How to Maintain the Ideal 40–60% Humidity Level at Home

Quick Checklist

✔ Ventilate regularly (or use an MVHR system)
✔ Monitor humidity with a hygrometer
✔ Use a humidifier if needed
✔ Replace filters on time (recommended every 3–6 months, depending on the manufacturer’s recommendations and your living environment)
✔ Do not ignore lingering odours or stuffy air

Optimal humidity indoors is not a minor detail. It is directly connected to your comfort, sleep quality and long-term health.

An MVHR system can help maintain the right balance – but only when it operates at full efficiency.

And that means:

With clean MVHR filters.

If you are not sure when you last replaced your filters, now is the right time to do it.

👉 You can find the right filters for your MVHR unit at “Filtrų pasaulis” – helping ensure your home is not only warm and comfortable, but also healthy to live in.