This paper deals with the assessment of the indoor environmental quality (IEQ) in two selected offices of the newly built green administrative building, which has achieved the second highest level of evaluation within the international LEED certification. The assessment of the IEQ was performed through real measurements of IEQ factors and a questionnaire survey. In each office, the total measurement time was set at 24 hours. The data recorded during the 8-hour working time were evaluated separately. During working hours, five employees were present in the first office (larger in area) and two in the second. Measurements were performed under natural conditions. For comparison, 24-hour measurements were repeated in the second office but witho...