In recent years, life cycle assessment has become an important tool for determining the environmental impact of materials and products. It is also useful in analysing the impact of a building structure has over the course of its life cycle which includes production of materials, transport, construction, operation, end of life. This paper is intended to provide a life cycle analysis of a building located in Coimbra, Portugal. To achieve the effect of different insulation layers, glazing type and window shading, two different solutions were analysed. In order to compute the thermal transmittance U-values for the walls and roofs, Therm5 software was used, so as to account for the effect of thermal bridges induced by the steel framework. These values were then introduced in the building model, which was designed in the software DesignBuilder, in order to compute the thermal behaviour of the building. Finally, the values of the energy consumption for a period of 50 years were introduced in the life cycle analysis made in the GaBi software. This allowed estimating the impact of both solutions and providing conclusions as to which is the best solution.