In Sweden, the long-term climate goal is to achieve a net zero emission of greenhouse gases by 2045. At the same time, today the Swedish construction and property industry accounts for 21 percent of all greenhouse gas emissions, and the use of more climate-friendly materials can be part of the solution. The aim of the study is to analyze the climate impact and costs from a nine-floor building, where four different frame systems are compared. The nine-floor building is of a normal concrete frame with load-bearing steel columns in the outer walls. This building will then be compared against if the building was made of green climate-compensated concrete. As well as two hybrid solutions where the top three floors are dimensioned to a wooden frame and six floors in gray and green concrete below. In order to analyze the climate impact and costs, a life cycle analysis (LCA) and a life cycle cost analysis (LCC) will be carried out using the One Click LCA tool. In the life cycle analysis, the stages (A1-A5) will be studied and in the life cycle cost analysis the material costs (A1-A3) will be studied. The result from the life cycle analysis shows that the hybrid building with wood and green concrete has the lowest climate impact in terms of emissions of carbon dioxide equivalents (CO2e), followed by the building in green concrete. The result also shows that the hybrid building with wood and green concrete has approximately 43% lower climate impact compared to the gray concrete building which had the largest. The life cycle cost analysis shows that the gray concrete building has the lowest material costs, while the hybrid building with wood and green concrete has the highest. The conclusions of the study are that dimensioning a wooden frame meant thicker building parts compared to a concrete frame, which resulted in a smaller living area. But the hybrid buildings with three floors with a wooden frame, on the other hand, had a significantly smaller climate impact compared to the respective concrete building.

Ninety percent of all single-family houses and smaller residential buildings in Sweden are built with timber frames. Though, this figure is different for higher buildings, about twenty percent in timber frames and eighty percent in concrete and steel. However, the knowledge and experience about tall timber houses is limited today and it needs to be developed over the time, both technically and architecturally. Purpose: The wood has a lower E-module than concrete and steel, which cause an additional problem in high-rise buildings of more than eight floors, stability. The measures for this problem can be costly and reduce the living space of the building due to large dimensions of the wooden structure. This project work is based on the challenges that exist around the construction of tall wooden buildings and tries to present a beneficial hybrid solution for the construction of tall houses in wood and concrete. Method: The study object is a multi-story building on ten floors where wood is used in combination with concrete for the frame system. The vertical loads such as self-weight, payload and snow load are carried by the wooden frame. On the other hand, concrete has the task of taking care of the horizontal forces caused by wind loads. The frame system is dimensioned according to the Eurocodes and standard dimensions to ensure the load-bearing capacity of the building. Results: The result reports that two concrete cores in the hybrid building absorb all horizontal forces and loads down to the foundation. These cores can also be used as stair/elevator shafts and will not affect the building's living area. A timber-concrete composite with a thickness of 300 mm, replaced the wooden composite which normally reaches a thickness of 400 to 500 mm. This means a height gain of one to two meters. The columns will get smaller dimensions because of the cores and give more living space. The concrete utilization in that hybrid building decreases by 57 percent, which is a large saving from an environmental perspective. In addition, life cycle analysis, LCA shows that carbon dioxide equivalents, CO2e are 43 percent less in the hybrid framework. Conclusion: The hybrid multi-stories houses of concrete and wood can be a useful alternative for increasing construction of wooden houses. A concrete core in the middle of building helps the construction to become more stable and the swaying due to wind loads be minimized. Furthermore, the columns can have smaller dimensions, which increases the living space in the building. The timber-concrete composite gives the building more weight and solves the step sound problem that arises due to low E-module on the wooden flooring. Additionally, the height of the building decreases, which in turn leads to buildings being able to have more stories and more living space. Moreover, through hybrid solutions in buildings, the environmental benefits of wood can be utilized to build environmentally friendly buildings. The ten-stories hybrid framework in this study, saves 43 percent CO2e compared to the corresponding framework in concrete.