The use of thermal mass and phase change material to reduce a building's 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 required climate conditions for thermal mass and phase change material to reduce thermal transmission are given. The maximum reduction in net thermal transmission is given for both thermal mass and phase change material. Equations are given to calculate the minimum thermal load resulting from thermal mass and therefore the maximum thermal load reduction with thermal mass. Equations and methods are given to calculate the minimum thermal load resulting from thermal mass from weather data files, TMY or TMY2 files.;The IECC, International Energy Conservation Code, allows for a reduction in R-value and/or an increase in U-factor of the exterior wall of a building with the incorporation of what it defines as a MASS WALL within the wall. A study is conducted to determine the required U-factor of the MASS WALL for it to perform with equal net thermal transmission and net thermal load, under transient ambient sol-air temperature conditions, as the required U-factor of the no-mass wall. The IECC defines eight CLIMATE ZONES with different requirements for each. The required U-factors are given for four of the zones. A finite-difference model was developed specifically to simulate the BESTEST qualification cases. This model is used to verify the results obtained when applied within the entire building envelope.;A test cell is constructed with a heater and a thermostat within the cell to maintain the interior air temperature at a predetermined set point. The test cell is placed in the ambient cyclic weather conditions. Data is logged of the temperature of the interior cell air, mass wall surfaces, and the ambient air. The amount of energy required to maintain the cell at the set point is also logged. The test cell is placed in different cyclic weather temperature conditions with respect to the interior cell set point temperature. The logged data verifies the conclusions offered resulting from the finite-difference study.