We present an ongoing project which aims at monitoring IAQ in multi-apartment buildings (MABs) before and after renovation. We collect measures of indoor air microclimate parameters in 6 apartments of 3 MABs of standard construction buildings (type 464) in Riga, during the heating season of 2010/2011. In 3 apartments of one renovated building and in 3 apartments of two unrenovated buildings (on the first, middle and top floor), sensors of air temperature, relative humidity, CO2 concentration level, and air flow velocity are located to find the average value of IAQ parameters, and to make calculations of indoor air exchange in each apartment. At the same time, outdoor air temperature and relative humidity are measured. The measurements are made every minute, and the paper presents data for the duration of several months. In general, the results show that ventilation system must be updated in all apartments. The thermal energy for heating is reduced by about 50% in renovated MAB. Heat energy consumption in different apartments of the renovated building and temperature measures in all the project apartments demonstrate the necessity to change the heat consumption according to individual financial possibilities and comfort demands.