Managing indoor humidity is a natural part of looking after your home, whether you live in an older house or a modern apartment. By understanding how moisture works, you can easily create an environment that feels light and comfortable, while protecting the building's structure and materials.
However, it is worth noting that humidity challenges are rarely about the air in the whole room. In many cases, situations arise locally when warm and humid air meets cooler parts of the building where condensation can form.
To maintain a good balance in the home, it is therefore useful to understand what levels are appropriate, why variations occur and what measures contribute to a stable indoor environment.
Humidity is measured in relative humidity (RH) and is expressed as a percentage. It shows how much moisture the air contains in relation to the maximum amount of moisture it can carry at a given temperature.
As warm air can carry more moisture than cold air, the relative humidity changes when the temperature changes - even if the actual amount of moisture in the air remains the same.
In dwellings, a normal and balanced level is often between 40-60% RH. When the level remains above about 65-70% for long periods, it is good to pay extra attention to ventilation, especially in cooler areas.
| Relative humidity (RH) | Assessment | Listing |
|---|---|---|
| Under 30% | Very dry air | Common during cold winter periods; can be noticed on static electricity |
| 30-40% | Dry air | A normal level in Sweden for much of the heating season |
| 40-60% | Balanced level | Provides good living comfort and is gentle on furnishings and materials |
| 60-75% | Higher moisture level | Here you should pay extra attention to ventilation and cold surfaces |
| About 75% | High level | At these levels over time, measures to reduce moisture should be considered |
It often starts with measuring to get a clearer picture of the moisture balance in your home. A simple first step is to use a hygrometer, which shows the relative humidity in per cent.
Place the hygrometer in the so-called occupied zone - preferably at chest height in the room where you spend most time. Avoid placing it directly next to windows, exterior walls, radiators or in direct sunlight, as localised temperature changes can give misleading readings.
To get a more accurate picture, it may be interesting to observe the values at different times, for example:
A simple hygrometer gives a good indication for home use. If a more in-depth analysis is needed or if there are recurring concerns, it may be wise to use calibrated equipment or to consult a professional for a ventilation check.
These signs are often more noticeable in late summer when warm outdoor air meets cooler spaces like basements or crawl spaces.
If the air is not replaced at a sufficient rate, the natural moisture from everyday life stays in the home for longer than desirable.
When warm, moist air meets cold surfaces, condensation forms. This happens most often:
It is natural for a family to add between 5-10 litres of moisture per day through activities such as cooking, washing, plants and exhaled air.
Some parts of the house, such as crawl spaces or cold attics, are more affected by the surrounding environment and may require a little more care in terms of insulation and ventilation.
Today's airtight houses save energy, but require more balanced ventilation to remove excess moisture.
When moisture levels are high for prolonged periods, it is wise to act to maintain the good condition of materials. This mainly involves preventing moisture from adhering to organic materials, as this ultimately affects living comfort.
Challenges often arise not in the centre of the room, but at so-called cold bridges - places where the surface is colder than the surroundings. This can happen, for example:
Paying attention to these places and ensuring that air can circulate freely creates favourable conditions.
Possible consequences of imbalance:
Effective ventilation replaces moist air with fresh outdoor air. For villas, an FTX unit can be an excellent solution that contributes to:
It's a good idea to leave the bathroom fan or kitchen fan running for a little extra time after use to help get the moisture out of the house.
Use lids when cooking and try to avoid drying laundry indoors if the ventilation is not designed for it.
A quick and intense cross-draft for a few minutes is often more effective than leaving a window ajar for a long time. It effectively exchanges the air without cooling down the materials in the room. In homes with functioning mechanical ventilation, this is often done automatically.
In spaces where ventilation is insufficient, a dehumidifier be a very helpful complement:
