slPCMlib predicts the effective thermal properties of solid/liquid phase change materials (PCM) showing a non-isothermal phase transition behavior. The effective properties are valid over the PCM functional temperature range where latent heat is absorbed and released. Different phenomenological phase transition models are implemented to account for temperature shifts in latent transition changes, e.g. due to multi-step transitions and thermal hysteresis. The library currently contains generic PCM and specific commercial paraffin-based and hydrated salt-based PCM (media). Its purpose is the analysis of partial and complete melting and solidification processes relevant for engineering applications, such as the design of PCM-enhanced building components.