In Switzerland, the advantages of timber buildings for the climate are broadly discussed. In the following paper, a comparative sustainability assessment of four building alternatives is presented. Especially the contribution of implementing Swiss timber versus the implementation of imported timber is highlighted. Additionally, the timber-hybrid building structures are compared to a pure reinforced concrete structure. The timber-hybrid structure, with Swiss timber, has clear ecological advantages with only half the greenhouse gas emissions and half the non-renewable energy consumption compared to the reinforced concrete alternative. Comparing the Swiss timber alternative to the imported timber alternative, there are clear ecological advantages, as well. In terms of economic and social sustainability assessment criteria, the reinforced concrete alternative has the lowest production costs and the lowest labor intensity (measured in terms of full-time equivalents). Additionally, the paper includes an analysis of biogenic CO2 emissions and CO2 storage within the timber building alternatives. Finally, an up-scaling to the national level is attempted, showcasing the ecological and economic advantages of promoting the use of locally produced timber.