The use of thermal infrared (IR) imaging is a valuable tool for inspecting and performing non-destructive testing of building elements, detecting where and how energy is leaking from a building's envelope, collecting data for clarifying the operating conditions of hard to reach heating, ventilating and air-conditioning (HVAC) installations, identifying problems with the electrical and mechanical installations under full-load operating conditions. IR inspections involve the detection of IR electromagnetic radiation emitted by the inspected object. The collected information can be used as part of other investigative procedures to identify potential problems, quantify potential energy savings, schedule interventions and set priorities for preventive and predictive maintenance or the need for immediate service to minimise the risk of failure, This paper reviews the main areas for using IR in building diagnostics with an emphasis on how it was implemented to support office building audits following the TOBUS methodology. Representative examples from building envelope, mechanical and electrical inspections in audited Hellenic office buildings are presented to demonstrate common problems and data interpretation.