Whereas previous building projects relied on air exchange via window crevices, modern flats inside low-energy buildings are an almost hermetically sealed system. Therefore, an air-conditioning system takes care of adequate air exchange.

Thanks to heat recovery, fresh air is warmed by the exhaust air, which prevents heat losses through ventilation. The heat that is generated in the flat stays inside, and the fresh air from outside arrives prewarmed to a comfortable temperature.

Each heat recovery unit also has an additional electrical warming system, which is sufficient for heating the low-energy flat with minimal energy consumption.

The powerful air-conditioning system with heat recovery units exchanges at least 10% of the air volume in the flat every hour. Therefore, all the air in the flat is exchanged within ten hours, which has a positive effect on the air quality from the point of view of the carbon dioxide content, odour, and air humidity. The whole system is adjustable and its output can be increased several times.

Each flat has two separately adjustable branches – one provides air exhaust from the kitchen, the other one from the rest of the flat. It is therefore possible, e.g., to increase the exhaust of kitchen vapours while cooking and leave the ventilation in the rest of the flat on the minimum level.

The air-conditioning unit in the SMART project is expanded with cooling of the incoming air in summer (by about 10°C, which is much better from the health point of view than when using closed-circuit air-conditioning). A single device performing both functions provides both cooling and heating of the system. A local electrical air warming system is installed in each flat, enabling additional warming of the incoming air for each flat.

Every user will understand the advantages of this system later from personal experience. nevertheless, we can say that generally it results in an improved overall user comfort in the flat, and users of this system have only given us positive feedback, chiefly for the following reasons:

The air ventilation is not in shocks – this means you can avoid temperature differences, not only leading to increased living comfort but also appreciated by pot plants sensitive to temperature changes
• The fresh air is pre-warmed by the waste air, significantly reducing the energy consumption for heating
• The air exchange is adjustable. About 10% of the air in the flat is exchanged every hour at the lowest setting, which ensures a pleasant environment without dust and moisture without perceptible ventilation
• The air-conditioning system significantly increases the healthy living comfort – no steaming on windows, no moist corners and prevention of mould
• The air exhaust from the kitchen ventilates the entire room, not just the area over the stove. Of course a closed-circuit hood with a carbon filter can be added over the cooking area to provide partial local filtering of the cooking odour
• The system is noiseless – there are no fans in the flats, a separate air-conditioning unit is installed in the basement of each apartment building