Previous experience shows that renovation of ventilation system is not a typical component of renovation of multi-apartment buildings (MABs) in Latvia. As a consequence, rooms are not ventilated enough and indoor air quality (IAQ) is reduced. This, in turn, leads to progression of the so called sick building syndrome (SBS). IAQ measures in 13 unrenovated MABs shows that CO2 concentration in 19 of the examined 30 apartments was ≥1000, indicating insufficient ventilation [2]. We present an ongoing project which aims at monitoring IAQ in MABs before and after renovation. We collect measures of indoor air microclimate parameters in 8 (eventually 12) apartments of 5 MABs in Riga, during the heating season of 2010/2011. The measures are collected in two types of standard construction buildings, the so called project type 464 and project type 602, in three and two buildings of each type, where one is renovated and the other is not renovated. Now in 6 apartments of three type 464 buildings (on the first, middle and top floor) and in 2 apartments of two type 602 building (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 total number of measured parameters is 55 (eventually planned till 98). The measurements are made every minute, and the paper presents data for the duration of 1 to 3 months. The results of the measures make it possible to find and to compare IAQ parameters and energy efficiency in MABs before and after the renovation.