How Much Better Is the Thermal Insulation Performance of UHPC Panels Than Ordinary Concrete Panels? Thermal Parameter Comparison and Energy-Saving Value Analysis

The difference in thermal insulation (more precisely, thermal resistance) performance between UHPC panels and ordinary concrete panels mainly stems from UHPC's extremely high density and lower moisture content, but these result in a typically higher thermal conductivity. Therefore, the insulation performance of UHPC panels alone is generally not superior to that of ordinary concrete; however, their excellent mechanical properties make it possible to achieve more efficient and thinner composite insulation assemblies, thereby delivering outstanding energy-saving performance for the overall building envelope.

In terms of the material's own thermophysical parameters, ordinary C30 concrete has a thermal conductivity (λ) of approximately 1.7–2.0 W/(m·K), while UHPC, owing to its extremely low porosity and dense microstructure, typically has a higher thermal conductivity, reaching 2.2–2.5 W/(m·K). This means that, at the same thickness, a pure UHPC panel actually conducts heat more readily. However, the thermal insulation performance of a building's exterior wall is not determined by a single material layer, but by the entire wall system, including the insulation layer.

The core advantage of UHPC lies in its "high strength, reduced thickness" characteristics. With flexural strength more than 5 times that of ordinary concrete, UHPC decorative panels can be made very thin (e.g., 15–25 mm) while still serving as a reliable substrate. The saved thickness can be used to increase the thickness of high-efficiency insulation materials (such as rock wool or vacuum insulation panels). For example, a traditional stone curtain wall (30 mm stone + 100 mm insulation) may have an overall heat transfer coefficient (K-value) of around 0.45 W/(m²·K), whereas using 20 mm thin UHPC panels allows the insulation layer to be increased to 120 mm or more at the same overall visual thickness, easily lowering the K-value below 0.25 W/(m²·K) and improving energy efficiency by more than 40%.

In addition, UHPC curtain wall systems typically adopt open or closed back-ventilated constructions, where the intermediate cavity layer effectively cuts off thermal bridges and promotes air circulation, further enhancing overall thermal performance. In several ultra-low energy consumption building projects participated in by Qinglong Group, we leveraged the high-strength, thin-profile characteristics of UHPC to design a composite system of "ultra-thin UHPC decorative panels + thick high-efficiency insulation + inner structural wall", achieving a perfect unity of decorative effect and energy-saving performance. Therefore, when evaluating the thermal insulation performance of UHPC, one should focus on the high-performance composite systems it enables, rather than on the thermal conductivity of the material alone.