Air quality and ventilation at home

What gets measured

• CO2: rises with the people present and is the best indicator of poor ventilation. Above roughly 1,000 parts per million, the air is generally considered in need of renewal.
• Relative humidity: too high encourages mould and condensation; too low dries out airways, common in winter with heating on.
• Volatile compounds and particles: cooking, cleaning products, fireplaces.
• Temperature.

How ventilation works

• Mechanical ventilation with heat recovery: renews the air while recovering much of the heat from the outgoing air. It's the usual solution in efficient homes.
• Extraction in bathrooms and kitchen.
• Windows: manual or motorised.

What automation does

• Ventilate on demand: ventilation ramps up when CO2 or humidity rises and down when nobody's home, instead of always running at the same rate.
• Bathroom extractor that starts with humidity and stops on its own.
• A prompt to open windows, or opening of motorised ones.
• Pausing heating in a room while its window is open.
• Night cooling in summer, when outside air is cooler.

In mountain homes

In winter people ventilate little because of the cold, and indoor humidity rises: cooking, showers, drying laundry. In second homes shut up for weeks, the risk of condensation and mould is greater. A humidity sensor with an alert and a programmed minimum ventilation rate prevent it.

In offices, classrooms and meeting rooms

In busy spaces, CO2 rises quickly and affects comfort and concentration. A visible sensor, or one connected to the ventilation, keeps the air in good condition without relying on someone remembering to open a window.

Where to put the sensors

• At breathing height, away from windows, doors and air vents.
• In the rooms where most time is spent: bedrooms, living room, study.
• Humidity sensors in bathrooms and the utility room.

Maintenance

Mechanical ventilation filters should be changed as the manufacturer specifies. The automation system can remind you based on running hours.