In-situ measurements of a case study building located in Riga old town near the river Daugava has been carried out in this work. Performed measurements are moisture level of historic masonry, and interstitial monitoring of temperature and relative humidity between the layers of internal insulation and external wall. Obtained results are compared with outdoor weather data. Results show that during the cold months of the year no rising damp problem. No interstitial condensation under the internal insulation, and no risk of mold growth occur. However, the façade of the building tends to be highly influenced by the outdoor weather, and the moisture of the masonry increases during the rain load events.