Health risks of adverse relative humidity


Relative Humidity of around 50% in the home or workplace is crucial for your health. If conditions are too dry or too damp it affects the levels of Bacteria, Viruses, Moulds, and Dust Mites. Poor conditions affect infections, allergies, and also hair and skin.

Research shows that home and workplace climates in the range of 40%-60% RH are the healthiest conditions in which to live.


Managing relative humidity is of growing importance as a result of the the continuing construction of energy efficient buildings. Low fresh air ventilation rates and highly effective heating systems create conditions where pathogens and allergens can thrive and concentrate. In winter, increased internal temperatures can create excessively dry environments that cause 'winter itch' and cause skin and lips to crack.

In winter buildings are hotter and drier than they have ever been before. The effects of this dryness can also be seen on wooden items such as the wood floors that we have in our homes. Dry conditions cause floors to gap and crack, so if low RH% can crack wood it is hardly surprising that it damages our health as well.

Historically houses were not able to be kept warm and sealed enough to allow them to dry out quite as much as they do now. Some people argue about the effect of climate change and global warming, however it is clear that our indoor climates have got much warmer and drier through energy efficiency measures.

In many other countries it has been customary for humidity controls to be included in properties, however in the UK it has not been standard practice. However, the trends in current indoor climatic conditions mean that humidity control is now the informed choice for owners and architects. 

Max. Bacteria infection: 0-30%, and 60-100%
Max. Virus infection: 0-50% and 70-100%
Fungal Growth: 60% - 100%
Dust Mite growth: 50% - 100%



In the UK our climate varies significantly through the seasons with indoor RH% being generally high during the summer months and RH% generally low during the winter. This means that we often need to take active steps to increase humidity in the winter and reduce humidity in the summer.

In order to know what action to take we need to first measure the indoor relative humidity. There are a number of ways to do this, and a good quality room Thermo Hygrometer is an inexpensive way to be able to monitor what is happening in a room. We sell an inexpensive really attractive Thermo Hygrometer that you can buy by clicking here.

Relative Humidity can change quite quickly, so it is often more useful to know the longer term trends of humidity within a room. A good way to do this is using a Fidbox electronic monitoring system embedded in the floor. This records the longer term climatic trends in a room and helps you understand what needs to be done to improve your climatic air quality and create the healthiest conditions for your home or workplace.

Please click here for more information about the Fidbox electronic measuring system, click here for Room Thermo-hygrometer, and click here to find out how to control humidity levels


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