This study aims to enhance the Environmental Performance (EP) of structural elements focusing on isostatic beams to mitigate the construction sector’s impact. The objective of the study is to determine the optimum typology and geometry to maximize EP for a given span and load. The methodology presented is twofold: first, minimising embodied emissions by optimizing beam characteristics, including geometry; second, comparing various beam typologies such as reinforced concrete (rectangular, I-shaped, shear-optimised), prestressed, steel, and timber beams. Cost data is integrated to provide information on the increase in cost relative to a given increase in EP. Results show that optimizing sizing often comes down to maximising the inertia. The EP ranking of beams varies with span and Life Cycle Assessment (LCA) assumptions, highlighting different impact reduction levers. LCA assumptions can cause EP values to vary by up to 42 %. Minimisation of cost and EP is related for most beams, driven by material volume minimisation. These findings highlight the importance of selecting appropriate LCA assumptions when optimizing a given beam. Strategies involving simultaneous optimisation of cost and EP are effective in limiting the increase of cost relative to an increase in EP.