The Effects of Thermal Mass and Phase Change Material on a Buildings’ Thermal Load

A finite-difference model is used to simulate the effects of thermal mass and phase change material on thermal transmission through a building’s envelope wall. The exterior temperature is simulated by a sinusoidal function. The inside temperature is held constant. A comparison is given between the effects of thermal mass and phase change material. The maximum reduction in thermal load and required conditions is given for both thermal mass and phase change material. Equations are given for the maximum thermal load reduction as a function of the inside and outside temperature. Equations are also given which treat the thermal mass as a lumped capacitance and the expected error as a function of the amount of thermal mass. The conditions under which the addition of thermal mass and/or phase change material will result in a reduction of thermal load is given.