Thermal mass can reduce peak cooling loads and indoor air temperature swings in buildings. The factors affecting the performance of thermal mass are reviewed and classified. Experimental studies which demonstrate the effectiveness of thermal mass as an energy conservation alternative and in providing more comfortable indoor conditions, are also reviewed. A number of simplified design tools for calculating the cooling load and indoor air temperatures of a building, which also account for thermal mass effects, have been identified and are classified. The models are categorized in terms of their inputs, outputs and restrictions on their level of accuracy in treating thermal mass effects, type of loads or other design limitations.