• The temperature of the radiator.
• Temperature in the classroom.
• Humidity.
• CO₂ concentration.

Below you find monitoring results from a two-week period 8-17 December 2003 with the lowest outside temperature. 13-14 December is a weekend.

Heat recovery unit operation:

1. Estimated efficiency of heat recovery with current airflow is approx. 80% (min. 75%, max. 88%).
2. With estimated air flow volume 500 m³/h and in Warsaw climatic conditions we obtain energy savings of 10,500 kWh.
3. Air is heated by heat exchanger about 15-20^o C.
4. In the classroom without the ventilation unit the air temperature increases and humidity is higher. This proves a better air exchange in the room with the heat exchange ventilation unit.
5. Higher increases of water vapor content in the classroom without the unit indicates worse air exchange.

Due to the fact that the ventilation unit was only mounted in one classroom, it is difficult to present a total energy reduction for the whole school. But as it is presented above the positive aspect of such a solution is evident.