In building construction, the use of phase change materials (PCMs) allows the storage/release of energy from the solar radiation and/or internal loads. The application of such materials for lightweight construction (e.g., a wood house) makes it possible to improve thermal comfort and reduce energy consumption. However, in order to assess and optimize phase change materials included in building wall, numerical simulation is mandatory. For that purpose, a new TRNSYS Type, named Type 260, is developed to model the thermal behavior of an external wall with PCM. This model is presented in this paper and validated using experimental data from the literature. (C) 2010 Elsevier B.V. All rights reserved.