This paper studies the thermal performance of a small thermally massive test cell built by the Korea Institute of Energy Research (KIER) located in Daejeon, Korea. The cell is 3 m wide, 3โข6 m long and 2โข6 m high. It is built mainly with concrete and cement bricks. A partition wall divides the interior of the building (cell) into two zones: a living and a buffer zone. Space heating of the building is provided by coils carrying hot water imbedded in the massive floor. This case study was of special interest because the KIER test cell is significantly more massive than those previously tested using the same methodology by the National Renewable Energy Laboratory (NREL) in the United States. A series of short-term tests were conducted to evaluate the major heat flow terms which largely influence building performance. The test procedure and data analysis were carried out according to the PSTAR method developed by the NREL. Each test period was three days during which the building was unoccupied. The data measured with eight channels were used to renormalize an audit based simulation model of the building. Results show close agreements between the measured and renormalized values reflecting the effects of heavy thermal mass, whereas the simulation results from the audit description of the test cell deviate considerably. A long-term extrapolation has also been made from the weather data of Seoul TMY (Typical Meteorological Year) for the calculation of monthly heating and cooling loads. 1997