Hempcrete is a promising and modern self-bearing thermal insulation material, as it has low thermal conductivity and can provide negative CO2 emissions, i.e. more CO2 is stored in the material than generated during its production. It is used in the construction of new buildings, but it is accepted to believe that it can also be used in the renovation of existing and historical buildings, for example, insulating wooden buildings from the inside, because their hygrothermal properties are well compatible with wooden construction. The following study was conducted to assess such compatibility both experimentally and through modeling. A wooden multi-story building built in 1936 was used, which was insulated from the inside with experimentally made hemp blocks, relative humidity, temperature at different wall depths, as well as heat flow through the structure were measured with sensors, the data was used for modeling validation and mold growth risk assessment. The structure consists of cementlime plaster, pine, lime plaster and hempcrete. Due to the fact that the transfer of moisture and heat in the wall construction of the building are closely related, sensors were placed in the wall construction that collected data on humidity and temperature at the relevant points. The design model used in the experiment was created in the numerical modeling software WUFI. One-dimensional models were developed and the finite volume method was used. Experiments were performed to validate the numerical model and obtain indoor/outdoor temperature boundary conditions. The experiment was performed from 2017. April 9 to 2019. April 27 or ∼ 2 years. The numerical model for the temperature and humidity transport in wall insulation structure with hempcrete has given results that are good enough with experimental observations. In addition, the mold risk forecast, which is only derived from the numerical modeling results, coincides with the actual observations – that is, in both cases no mold risk was detected, and no mold was observed when looking at the design itself. This shows that the model of hempcrete material created in the constructions with other materials is adequate, which means that it can be used in other cases when the climatic conditions in Latvia are close enough to the observers.