The current tendencies concerning optimisation of maintenance parameters with regard to thermal comfort and indoor air quality in office and commercial buildings have been presented. The heating, ventilating and cooling systems for the indoor environment design have been characterized. Results of investigations regarding the indoor environment parameters for selected, representative buildings-a traditional, modernized building and an energy-efficient building-have been compared. In the energy-efficient building, a high diversity of indoor air quality (IAQ) has been demonstrated. Effective ways of indoor environment parameter optimisation in the aspect of outdoor air stream minimisation with reduction in carbon dioxide levels regarding human-occupied areas have been proposed.