Klimatoptimering av källargrundläggning för större byggnader

Sammanfattning: Due to increased environmental and climate awareness, great emphasis has been placed on both research and development of environmental impact of buildings. Scientific research on climate optimization of both structural frames and floors is well developed. However, equally large environmental improvements have not yet been made for foundations of large buildings. There are still no obvious alternatives to concrete as a building material for large foundation works. Concrete accounts for large proportions of the carbon dioxide emissions of the world and to reduce the volume used, more work is needed in order to optimize structural elements with regards to the climate footprint. To reduce the climate footprint of concrete, additives are usually used to reduce the cement content. Further research on concrete recipes is required to comply with climate goals. In order to further accelerate the reduction of concrete use, constructive optimizations of both volumes and design parameters have to be made. Hence, construction elements can be adapted and designed for their specific purpose, resulting in a reduction in use of materials. In this report, the use and design of basement walls are analyzed from a climate footprint perspective. This type of construction is often designed on the basis of tougher demands than what is needed. The analysis, in this report, is based on design parameters and how these affect the emission of carbon dioxide. The input parameters that are studied are exposure class, concrete cover and allowable crack widths. Based on these criteria, the basement walls are designed according to different usage and geotechnical conditions. Focus is placed on whether the basement is being used as a vehicle garage or as a normal storage space, which affects the requirements placed on the construction. Another aspect that also is analyzed is to what extent stainless steel reinforcement may be implemented and what possible benefits this may provide for the climate. Results, from this report, indicate tendencies that environmental improvements can be made by selecting input parameters carefully after thoroughly examining the real preconditions. By reducing the wall thickness by 20 mm, carbon dioxide emissions from basement walls can be decreased by 5–10%. The estimations also indicates that emissions can be reduced by 25% if the basement is planned to be used as a storage space instead of a vehicle garage. The reduction of emissions is based on the selection of a lower exposure class, which leads to a relief in the requirements on the concrete and the reinforcement. The analysis of the implementation of stainless steel reinforcement indicates that reductions also could be made in the requirements for the concrete structure. When used as a vehicle garage, carbon dioxide emissions can be reduced by 5–10% if stainless steel is used instead of classic carbon steel. A survey on how different companies design and select input parameters for basement walls was also carried out. Results from the survey indicate that both the choice of input data and wall thicknesses differ between the companies. To enable for the construction industry to comply with the climate goals that have been set, it is required that future building parts are specially adapted according to environmental conditions and that an environmental awareness is already introduced in the early design phase.