Sensible heat storage in building materials has been practiced for thousands of years. Recent work at the Centre for Building Studies of Concordia University on the incorporation of various phase change materials (PCMs) in gypsum wallboard has resulted in the addition of their latent heat values to the sensible heat storage value of wallboard. In this way its heat storage capacity can be increased by at least eightfold. PCM-wallboard development tests were conducted on a small scale using DSC analysis for selecting the PCMs; evaluating PCM-wallboard prototypes; to ascertain the reproducibility of PCM thermal characteristics in wallboard, to verify the spatial uniformity of PCM and to ascertain the effects of temperature cycling on the thermal characteristics of PCM-wallboard.