The introduction of innovative technologies and solutions and the adaptation of existing building resources to the standards of energy-efficient construction combines economic effects with care for the health and comfort of users as well as limiting the negative impact of buildings on the environment and climate. The thermal modernization of buildings is one way of saving energy. It is estimated that households are the largest heat consumers. In the article, the analysis of the effects of heat consumption reduction was performed for multi-family buildings. The basic effects of thermal modernization relate to economic issues associated with the reduction of fuel, water and electricity consumption, and thus incurred fees. The effects also refer to reducing the amount of air pollution, improving indoor microclimate conditions and user safety, as well as eliminating energy poverty and stimulating public awareness of energy-saving activities.