Despite the advancements in validation methodologies for building energy simulation tools, the validation process is still time consuming and difficult. This is mainly because the validation process has inherited the inadequacies of the associated simulation tools. In order to alleviate much of the limitations and obstacles encountered with current validation methods, a new validation module is developed. This paper describes the development and integration of a user friendly validation module (VLD) that is integrated within a state-of-the-art, whole building simulation code. The simulation code, the ESP-r, has been selected by the European Commission as a reference program for building energy simulation. The module is designed in such a way that novice simulation users can easily use it, and it contains a number of features that enable potential simulation users to validate the simulation tool even before learning how to use it. Because of its speed and ease of use, the module can also be used by professional simulationists as a quality assurance tool and can be used by software developers to speed up validation of the simulation program after each major modification. The VLD is based on a general solution of the dynamic heat flow through opaque multi-layered building construction. The module is verified by comparison with exact analytical solutions. In addition, the practical application of the module for multi-layered construction is demonstrated.