Why is indoor air poor even though ventilation is on?
What is measured from indoor air
- Carbon dioxide. People produce carbon dioxide when they breathe, so a high concentration is usually a sign that the ventilation is not sufficient for the number of people in the space. The action limit in the Finnish Housing Health Decree is exceeded when the indoor concentration is 1,150 ppm higher than the outdoor concentration. When the limit is exceeded, the air feels stuffy and concentration slips.
- Relative humidity. In winter, heated indoor air is dry, and ventilation that is too effective dries it further. On the other hand, too little ventilation leaves the moisture from showers and cooking in the structures. Measurement tells which of the two problems the building has.
- Temperature. If supply air is blown in too cold in winter, it feels like a draught, even when the average room temperature is right. The temperature of the supply air and of the room are measured separately.
- Pressure difference. The pressure difference in the ventilation tells whether the air flow is sufficient and whether the filters are clogged. A clogged filter shows in the pressure difference months before it shows in the indoor air.
Why a constant power setting does not work
The ventilation in an apartment building is typically set to one power level that is sufficient for a full building. During the working day, when the flats are empty, the same power changes air that nobody is breathing and blows heated air outside. In the evening and at weekends, when the building is full, the same power may be too little, and carbon dioxide rises in the bedrooms during the night.
A time programme helps only if it matches how the building is really used. Measurement does not rely on an assumption about the hours of use, because it follows what actually happens in the building.
How automation corrects it
When ventilation is controlled according to carbon dioxide, humidity and temperature, the unit runs as much as is needed. In an empty building the power falls; in a full one it rises. The temperature of the supply air is kept even all year round, so it is neither cold in winter nor needlessly heated in summer. A clogging filter shows as an alarm before the ventilation weakens.
The same measurement improves indoor air and reduces the heating bill: ventilation is among the largest consumers of heat in an apartment building, and air changed unnecessarily is blown outside heated. Heat recovery takes part of it back, but ventilation controlled as needed is still the cheapest. District heating and heat recovery
We can connect measurement of carbon dioxide and relative humidity to our automation delivery, so that we control ventilation according to them. We add the measurement in buildings where the quality of the indoor air requires it.
Frequently asked questions
Is it enough to increase the ventilation?
No, if the problem is in the timing. A higher constant power dries the air further and raises the heating bill. The right solution is to control the power as needed, which requires measurement.
Is dry indoor air the fault of the ventilation?
Partly. In winter the outdoor air is dry, and the more of it is brought inside, the drier the indoor air becomes. Ventilation controlled as needed changes air only as much as the carbon dioxide requires, so the humidity stays tolerable.
Does measurement replace an indoor air investigation?
No. If moisture damage or microbes are suspected, an investigation of the structures is needed. Continuous measurement tells whether the ventilation works as designed and gives the investigation its starting data.
Is the state of the indoor air visible to residents?
Building-level data can be shown on an information display in the stairwell if the housing company wishes. Measurements from individual flats are visible to the property manager and the maintenance company. Kiinteistöpilvi