The 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 causes a change of living as well. New houses demands new responsibilities, for instance to ventilate. 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, odor, exhalations from furniture, paints, etc. 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 (outside air at -10°C and RH of 90%, warming up to 20°C the RH decreases 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 causes typical “winter” diseases!

Dry air benefits the growth of viruses and bacteria. It is not the cold temperature that makes us unimmunized – it is the concentration of viruses in the air. Especially indoors where people are closed together. 

We call it „influenza“
Dry air supports the time of abeyance for aerosols in the air. That causes infections of our respiratory tract or air passages. 

We call it „cold“
Moisture recovery with rotors was our first step to humidity control with the purpose to avoid too dry indoor air.
 

Why is it now sometimes necessary to limit the moisture recovery as well?

Nowadays a new challenge is coming up: there is often no time for investors to dry out the new built houses during the first winter! Therefore in more and more countries due to the development of house standard we are faced with too high humidity indoors. 

You can count on problems caused by too high humidity:

• In new built massive houses where the people moved in too early (before the first winter) when all the building moisture is still in. The people living inside will increase the humidity level even more. Here you can have RH about 70-80%. Our experience shows that even with ventilation system it takes 2-3 years (winters) to get the RH inside into a normal range.
• In new small flats where the residents causes too much moisture compared to the air volume of the flat. Here you can have RH above 70-80% as well. But in this case the high humidity often will stay.

We know that a RH above 60% increases the growth of mold and mold damages the building and causes allergies. That means in some cases we have to take care about the moisture transfer as well. 
The engineers from Systemair uses the possibility of rotor speed control with the new EC rotor drive to decrease the moisture transfer when needed. Therefore 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 a lot to keep the indoor humidity in a comfortable range.

Humidity transfer is also possible with the so called enthalpy counter flow exchangers but they cannot control it. 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 keep well.