Thermal Performance of Masonry Walls Strengthened with Glazed-Hollow-Bead-Modified ECC

Existing masonry buildings in severe-cold regions face the dual challenges of structural vulnerability and high heating demand. This study develops a glazed-hollow-bead-modified engineered cementitious composite (B-ECC) and evaluates its thermal performance at the material, wall-component, and building levels within an integrated retrofit strategy. At 50% volumetric sand replacement and 1.5% PVA-fiber content, a B-ECC achieved a thermal conductivity of 0.244 W/(m·K) (52% reduction) while retaining a compressive strength of 43.9 MPa. Wall-level finite-element analysis, validated by hot-box experiments (±5% error), showed that 20 mm overlays per face provide balanced thermal improvement. A whole-building case study of a three-story masonry teaching building in Changchun demonstrated that combining B-ECC overlays with insulation, window replacement, and heat-recovery ventilation reduced annual heating demand from 70,685 to 17,229 kWh/a, achieving a 75.6% energy-saving rate. The primary value of a B-ECC lies in enabling a coordinated structural–thermal retrofit.