Measured and modeled influence of the moisture buffer effect in a historic stone church and its influence on possible HVAC measures

Historic buildings often show a high thermal inertia, influencing the buildings thermal behavior. But not only thermal inertia, but also hygric inertia plays a significant role for the mean temperature and relative humidity and their fluctuations in those buildings. This paper presents measured values of temperature and humidity conditions in a historic massive stone church. The concept of moisture buffering is explained and discussed. To assess the influence of the hygric interaction of a building with its envelope in a simulation model, it is necessary to compute the coupled equations for energy and mass transfer in the building components. A hygrothermal whole building simulation software model of this church is presented and verified with the measured values to allow the assessment of the hygrothermal performance of this building. The verified model allows then to conclude on the effectiveness of different active and passive measures that might be implemented to ensure an indoor environment that fulfills preventive conservation requirements. Measurement results show a high influence of the hygric and thermal inertia on the indoor conditions. These indoor conditions were successfully modeled with a hygrothermal whole building model. It is shown, that it requires a thorough analysis to decide if passive measures can be preferred over active HVAC measures that demand more energy.