Most LCA studies lately have been dealing with the dilemmas which material is more energy-efficient to use: wood or steel, concrete or wood? Unlike to this perception this project takes the idea of Mediterranean vernacular architecture where it has been a tradition for long centuries to compose different – heavy and light-weight – materials in one building. We use Life Cycle Assessment and thermal numerical simulations to compare five houses, built either exclusively with one material or having both materials, either one at the ground floor and one in the first floor or one in all southern façades and the other in the northern walls. Our results show the interest of having massive and light-weight material located in two different places in the house. Especially in the Mediterranean climate it allows an optimal use of the space throughout the year.