Climate design and climate engineering are nowadays standard in the design process. The more successful we are in this, the less energy we need to run the building during its useful life and we can focus instead on an additional aspect: the embodied energy - the energy we need for the material production and construction process. Interestingly, the reduction in energy used in a climate-efficient building during its lifetime is equal to the energy consumption necessary to produce and install the building. This aspect triggers us to reconsider the design potentials of focusing on less energy in the construction. Which materials make sense energy-wise? Do we need to build with simple materials for 500 years or should we go high-tech and design the complete life cycle for a perfect reuse with maximum recyclable materials? Or should we build out of materials that can be used as energy after being a building? This publication focuses on the embodied energy aspects of building materials, their life cycle and their potentials for reuse as energy or in construction, and presents some far-reaching design ideas.