Historic buildings are a living representation of our past and it is our duty to ensure that future generations have access to their heritage. In order to accomplish this, it is necessary to determine the conditions that the buildings are in and, if needs be, to make the necessary changes. In this latter stage, it is helpful to have a validated whole building hygrothermal model since it takes into consideration most of the processes that affect their hygrothermal performance, thus allowing us to choose the most appropriate interventions. This paper aims to establish a validation process for historic buildings based on annual indoor conditions using simulation software. Hence, the indoor conditions is a 13th century church in Lisbon were monitored over a year. The model accuracy was assessed by comparing the simulated and measured temperature and water vapour pressure, and quantified using the coefficient of determination, coefficient of variation of the root mean square error, normalized mean bias error and goodness of fit. The hygrothermal model was then validated by comparison against other models in literature and existing standards/guidelines. Four outdoor weather files were simulated to show the importance of monitoring the outdoor climate as closely as possible to the case-study. The soil/slab interface temperature was obtained using six different models. A sensitivity analysis was developed to optimize some of the inputs. Ultimately, the church hygrothermal model was validated. However, in hygrothermal models the simulation time can be long, therefore, a simplified model was developed using two of the four tested simplifications.
