The renovation of buildings in middle and northern Europe should be coupled with an energetic improvement of the envelope parts. Often the preservation of the typical facades does not allow the use of an outside insulation. The application of an interior insulation, however, increases the risk of interstitial condensation. In a 200-year-old frame work house in East Saxony, Germany (fig.1) eight different inside insulations were tested. The ground floor of the building consists of a wooden beam wall, the first floor and the gable are a classical framework structure with a straw loam filling. The heat-transrnissivity coefficient of the old frame work wall is U = 1.8W/m²K. In the ground floor eight and in the first floor three different indoor insulation structures had been installed and investigated over a period of 4 years from October 1995 to October 1999. The surrounding climate components and the hygrothermic values withn the wall were continuously measured (Haupl et al. [I], Fechner et al. [2]). All measured results were compared to the results of numerical simulations with the computercode DIM 3.1. The software is based on the physical model of the coupled heat-, air-, moisture and salt transfer in porous building materials and building structures (Grunewald et al. [3], Plagge et al. [4], Haupl et al. [5]). In section 3 the numerical simulation of the hygrothermal behaviour of a silt wall belonging to a historical monument in Japan is presented. The wall is freely exposed to the natural climate. The simulations were performed with measured Japanese climate values. The results will be used to decide on preservation and renovation measures.