This work studies the thermal behavior of a new construction material: gypsum board containing 45% by weight of phase change materials (PCMs) reinforced with additives. A facility has been designed and built to simulate the hygrothermal conditions of any room or building. The influence of different parameters and variables regarding heat storage in buildings (air temperature, air velocity, material position, and so on) has been studied. The thermal storage capacity of different construction materials with similar use and position in buildings than boards with PCMs - laminated gypsum boards, bricks, etc. - has been evaluated and compared. It has been proved that a 1.5 cm-thick board of gypsum with PCMs stores 5 times the thermal energy of a laminated gypsum board, and the same energy as a 12 cm-thick brick wall within the comfort temperature range (20-30 degrees C). This work demonstrates the suitability of incorporating PCMs into gypsum hoards to increase heat storage capacity and to reduce energy consumption. (C) 2012 Elsevier B.V. All rights reserved.