Thermal bridges are areas of a building where heat is more likely to escape to the outside. They are caused by materials with different thermal conductivities, such as metal, concrete, or timber. Thermal bridges can lead to increased energy consumption, condensation, and structural damage. There are several things that can be done to reduce the impact of thermal bridges, including using insulation with high thermal resistance, using materials with low thermal conductivity, and properly installing windows and doors. This thesis examines the impact of thermal bridges on energy performance in factory built timber houses, focusing on a case study conducted by Vida Building AB in Alvesta. By analyzing thermal bridges by more than one method provides valuable insights. The average heat transfer coefficient was determined to be 0.243 W/m2K (from hand calculations) and 0.252 W/m2K (using Vip Energy program). Thermal bridges accounted for approximately 7% of total energy consumption in the studied apartments. The findings contribute to improving energy efficiency in residential construction by addressing thermal bridges according to Swedish building standards and climate conditions.