Most of energy in buildings in the Baltic states is used for heating, and therefore thermal insulation of building envelope as well as replacement of old wooden frame windows for PVC ones, have recently become one of the most commonly applied measures for energy conservation. However, energy improvement should not compromise health and comfort of building occupants, especially in kindergarten environments where both children and facility personnel can spend up to 12 hours per day. This study investigates the effect of implemented energy efficiency improvement measures on heating energy consumption and indoor climate in kindergartens in moderate climate zone of Latvia. Measurements of carbon dioxide, air temperature and relative humidity were carried out in six kindergartens (old, renovated and new-built), and data regarding heating energy consumption as well as kindergarten characteristics and maintenance activities was collected via combination of field visits, record analysis and interviews. This field study showed that different types of building construction as well as ventilation strategies employed by kindergartens can cause substantial variations in indoor air quality and comfort. It was found that most of time temperature and relative humidity was kept in a comfort range in all facilities. Carbon dioxide concentrations exceeded 1000 ppm in 75% of kindergartens studied, with the highest (1356 ppm) measured in a renovated facility with the natural ventilation system. Thus additional insulation of external walls should be accompanied by installation of more efficient ventilation system (mechanical) to account for air tightness, since opening of windows itself cannot provide optimal conditions indoors. The specific heating energy consumption during the year 2010 in four of six examined kindergartens varied between 196 and 285 kWh/m2, while the municipality goal is to reach as low as 100 kWh/m2yr. Therefore to reduce energy consumption, further actions should be taken, e.g. including HVAC system retrofit and use of high-efficiency HVAC equipment.