Capric acid (CA) and lauric acid (LA), as phase change materials (PCM), can be applied for energy storage in low temperature. The phase transition temperature and values of latent heat of eutectic mixtures of CA and LA are suitable for being incorporated with building materials to form phase change wallboards used for building energy storage. 120, 240 and 360 accelerated thermal cycle tests were conducted to study the changes in latent heat of fusion and melting temperature of phase change wallboards combined with the eutectic mixtures of CA and LA. Differential scanning calorimetry (DSC) tested the transition temperature and latent heat. The results showed that the melting temperature and latent heat of these phase change wallboards with eutectic mixtures have not obvious variations after repeated 360 thermal cycles, which proved that these phase change wallboards have good thermal stability for melting temperature and variations in latent heat of fusion for long time application. Therefore, they can be used for latent heat storage in the field of building energy conservation. (C) 2005 Elsevier B.V. All rights reserved.