Abstract:The contribution of embodied energy (EE) and greenhouse gas emissions to building materials and structures has been recognized as significant, especially for nearly-zero energy-efficient buildings. The aim of this paper is to evaluate the composition of non-transparent structures of building envelopes from energy and environmental perspectives using the life-cycle assessment method. The study assesses environmental indicators such as EE from non-renewable resources and CO2eq and SO2eq emissions from proposed assemblies of building structures for nearly-zero energy wooden houses. Material compositions are also calculated in terms of selected thermal-physical aspects (U-value, phase shift of thermal oscillation, relaxation time) to ensure the reduction of energy consumption during building operation. All results are compared using a multi-dimensional evaluation approach through mathematical methods. The multi-criteria decision analysis demonstrates that material optimization of building structures is possible to ensure a marked reduction of the energy consumption and carbon footprint of buildings.

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In world with limited amount of energy sources and with serious environmental pollution, interest in comparing the environmental embodied impacts of buildings using different structure systems and alternative building materials will be increased. This paper shows the significance of life cycle energy and carbon perspective and the material selection in reducing energy consumption and emissions production in the built environment. The study evaluates embodied environmental impacts of nearly zero energy residential structures. The environmental assessment uses framework of LCA within boundary: cradle to gate. Designed alternative scenarios of material compositions are also assessed in terms of energy effectiveness through selected thermal-physical parameters. This study uses multi-criteria decision analysis for making clearer selection between alternative scenarios. The results of MCDA show that alternative E from materials on nature plant base (wood, straw bales, massive wood panel) present possible way to sustainable perspective of nearly zero energy houses in Slovak republic

Intensity of building development increases by growing population and their requirements on living. Buildings belong to the largest energy consumers and greenhouse gases emitters. Current energy strategy of European Union is focused especially on reduction of operational energy of buildings. Although operational energy participates the highest proportion in total energy consumption over whole life cycle of building, it is important to take into account embodied energy. Values of embodied energy and associated emissions grow by improving energy quality of building envelope by using extra components and insulation materials. This paper demonstrates significance of correct selection of materials in order to environmental and energy optimalization of building structures. The designed material compositions of external wall alternatives are evaluated by methodology LCA and also in the view of impact on future energy consumption though thermal-physical parameters. Results of assessments are compared by multi-criteria decision analysis. The optimized alternative achieves very low embodied energy (218 MJ/m2) and high reduction of embodied CO2 (-114 kg CO2eq/m2).

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