HUMIDITY CONTROL
Humidity control at home
T
he housebuilding standard is changing rapidly due to the Ecodesign Directive because the use of energy is more and more limited. Less energy consumption can be achieved step by step with tighter and better insulated houses. These new houses cause a change of living as well. New houses demand new responsibilities – for instance, to ventilate – and It is not easy for people to get used to this. The result of poor ventilation is bad indoor air quality and very often high humidity.
The safest way to ensure right ventilation is to install a residential ventilation system that extracts used air, odour, exhalations from furniture and paints, and humidity in wet rooms like bathrooms or kitchens.
Why is it necessary to recover moisture in the wintertime? At cold outdoor temperatures the outside air has a low water content, and during heating it up the relative humidity (RH) will
decrease rapidly (with outside air at -10°C and RH of 90%, warming it up to 20°C reduces the RH down to 10%). Mixing constantly dry supply air with indoor air in wintertime, the indoor air humidity can go down to an uncomfortable and unhealthy level. It is not unusual to have RH indoors of 20% or even lower, which is much too low.
Dry air also causes typical ‘winter’ diseases, and benefits the growth of viruses and bacteria. It is not the cold temperature that makes us unimmunised – it is the concentration of viruses in the air. Especially indoors where people are close together. We call it ‘influenza’ Dry air supports the time of abeyance for aerosols in the air. That causes infections in our respiratory tract or air passages.
Moisture recovery with rotors was our first step to humidity control with the purpose of avoiding indoor air that was too dry.
Ventilation specialist Systemair covers the importance of recovering moisture in the winter.
Why is it now sometimes necessary to limit the moisture recovery as well? Nowadays, a new challenge is emerging: there is often no time for investors to dry out the newly built houses during the first winter. Therefore, in more and more countries due to the development of housing standards, we are faced with excessively high humidity indoors.
You can count on problems caused by humidity levels that are too high: ■ In very large new build houses where the people moved in too early (before the first winter) when all the building moisture is still retained, the people living inside will increase the humidity level even more. Here, you can have RH at about 70-80%. Our experience shows that even with ventilation system it takes two to three years (winters) to get the RH inside into a normal range.
■ In new, small flats where the residents cause too much moisture compared to the air volume of the flat. Here you can have RH above 70-80% as well, but the high humidity will often remain.
We know that a RH above 60% increases the growth of mould, and mould damages the building and causes allergies. That means, in some cases, we have to take care of moisture transfer too.
The engineers from Systemair use the capability of rotor speed control with the new EC rotor drive to decrease moisture transfer when needed. We have added a humidity sensor and EC rotor drive together with the new SAVECair control in all rotary units to offer these functions to all our users. This helps significantly to keep the indoor humidity within a comfortable range. Humidity transfer is also possible with the so called enthalpy counter flow exchangers, but they cannot control it. The best possible influence on indoor air quality is given by our new units with clean, filtered air, comfortable temperature and a humidity level that helps to ensure well-being.
18 September 2018
www.acr-news.com
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