In Sweden the housing sector stands for about 40% of the energy usage. About 20% of total energy usage goes to heating and hot tap water. Since 1920, the dominant building technology for single family houses in Sweden is a light timber-frame structure with studs at even spacing. This study aims to investigate how the static energy signature model can be used to estimate the effective U-values in existing wooden buildings and compare them to calculated U-values based on the thermal properties of the building parts. The results show that the energy signature model gives reasonable estimates of the U-value in a building. It is important though that a large difference in temperature can be achieved.