Lightweight steel-framed (LSF) structural elements in building construction provide a wayof increasing building sustainability. These structural elements present great potentialfor recycling and reuse, allowing the conservation of natural resources and theenvironment. When compared with other materials, these construction components alsoprovide other advantages: reduced weight with simultaneous high mechanical strength;easier prefabrication, allowing modular elements and higher quality control; shorterperiods for assembling the building on-site; no dimensional variations caused by moisture;and low cost. The high thermal conductivity of steel could be a drawback, leading tothermal bridges if not well designed and executed. In the case of LSF components (e.g.walls and slabs) it is necessary to take special care with the elements’ designoptimisation, with it being essential to use continuous thermal insulation. The buildingenvelope thermal performance is crucial to provide good thermal behaviour and energyefficiency, allowing a reduction of operational energy. In this paper, the LSFconstruction system is analysed in order to show its main advantages and drawbacks. Theassessment of embodied and operational energy is essential to perform a life cycleanalysis. The reduction of both energies’ consumption is crucial to increase thesustainability label. Special focus will be given to the mitigation strategies ofoperational energy in LSF construction.