This reprint of the Topical Collection: "Buildings' Thermal Behaviour and Energy Efficiency for a Sustainable Construction", published in journal Buildings (mpdi), includes 22 contributions (19 articles, 1 review, 1 perspective and 1 systematic review), from across the world, with very interesting and actual research topics, such as: Energy Resilience Performance; Indoor Air Quality; Chopped Straw as an Insulation Material; Energy Retrofitting Practices; Sustainability Assessment of Cementitious Ceramic Tile Adhesives; Solar Radiation of Deciduous Trees' Shade; Building Integrated Photovoltaics (BIPV) façades; Environmental Dissatisfaction and Underheating Lowers Self-Perceived Health; Parameters Measured to Characterize Classrooms' Indoor Environmental Quality; Uncertainty Assessment of Mean Radiant Temperature Estimation for Indoor Thermal Comfort; Energy, Environmental and Economic Costs of Buildings' Thermal Insulation; Retrofit Strategies on Thermal Insulation Applied in Buildings; Estimating Heating Load in Residential Buildings; Sustainable and Universal Approach to Retrofitting Residential Buildings; Optimum Building Envelope Parameters of a Room Concerning Window-to-Wall Ratio, Orientation, Insulation Thickness and Window Type; Thermo-Energy Performance of LSF Constructions; Reuse of Insulators from CDW to Produce Lime Mortars; Renovation of Modernist Architecture; Evaluation of Non-Autoclaved Aerated Concrete for Energy Behaviors; Water Vapour Resistivity Properties; Thermal Performance of Double-Pane LSF Walls with and without a Reflective Foil; BIM-Based Energy Analysis and Sustainability Assessment. .