Improving building energy efficiency and decreasing building energy consumption through monitoring of-heating, ventilation and air conditioning (HVAC) and heat recovery systems are becoming increasingly significant due to global energy crisis and carbon emission. Therefore, evaluation on building energy efficiency and energy conservation is extremely necessary. In the present work, energy conservation performance of one low-energy school building will be intensively investigated based on more than three-year measurement results from the monitoring system with sensor network. Heat recovery efficiency and new energy conservation parameter were analytically modeled, taking the building mechanical ventilation network into account. Following that, building energy performance has been experimentally investigated concerning the effects of mechanical ventilation rates, outdoor temperature and the efficiency of the heat recovery facility. Subsequent energy performance analysis demonstrates that building energy demands for ventilation and winter heating could be decreased with the enhancement of heat recovery efficiency of the ventilation facility, and the energy conservation ratio of the air conditioning unit increases with the temperature of supply fresh air. Diverse situations of energy conservation ratio and heat recovery efficiency have been detailedly correlated according to measurement results. (C) 2016 Elsevier B.V. All rights reserved.