To address the capacity mismatch between heat injection and thermal diffusion in thermally activated walls, this study proposes an enhanced thermally activated wall (ETAW) design to improve energy-storage efficiency and energy-saving potential. A dynamic heat transfer model is developed to compare the thermal performance of ETAW with that of conventional thermally activated walls (CTAW) and conventional energy-saving walls (CW). Local sensitivity analysis is conducted to investigate the economic impacts of fin parameters, climate conditions, and insulation thickness. Results demonstrate that ETAW exhibits significantly superior dynamic thermal performance relative to CTAW and CW, although the degree of improvement depends on the heat injection mode. Increases in trunk fin size and branch fin size both effectively reduce total operating energy consumption and costs, with the branch fin size exhibiting a more pronounced influence. Adopting a smaller branch-fin inclination angle (e. g. 60°) and a left-oriented installation can reduce operating costs and energy consumption by approximately 10.9% and 10.7% respectively. Insulation thickness shows strong correlations with energy efficiency and economic performance; recommended reduction rates should not exceed 40% in severe cold zones and may be extended to up to 60% in hot-summer zones.

Thermally activated building envelopes (TABEs) are multifunctional component that combines structural and energy properties. Based on re-examining the heat charging processes, an arc-shaped metal-fin-enhanced TABE (Arc-finTABE) with directional heat charging features is proposed to optimize the thermal barrier formation process. A comprehensive parameterized analysis is conducted based on a validated mathematical model to explore the influence of 5 fin-structure design parameters and the static insulation thickness. Results verified that the directional charging strengthening fins can improve transient thermal performances of Arc-finATBE and enlarge horizontal and vertical sizes of the thermal energy accumulation area surrounding the pipeline, while the maximum growth in extra heat loss is less than 3.17%. From the perspective of promoting heat injection into expected areas, the straight main fin configurations with the angle of main fins of 30°, shank length ratio of 0.4 and no leftward mounted fins are preferred in load-reduction mode, while the angle of main fins of 150°, shank length ratio of 0.8 and multiple fin designs, especially with one of the main fins horizontally toward the indoor side, are more favorable in auxiliary-heating mode. Besides, it is recommended to add one arc-shaped branch fin to each main fin to achieve a balance between performance improvement and material usage. Moreover, branch fins with larger arc angles are preferred in auxiliary-heating mode, while smaller arc angles are conducive to injecting heat into the wall along main fins in load-reduction mode and preventing the heat near the inner surface from being extracted. Under the direct influence of the strengthened invisible thermal barrier, Arc-finTABEs can reduce the amount of static insulation layer by 20%–80% while achieving equivalent thermal performances as conventional high-performance walls.

A modular thermo-activated wall (MTAW) with specialized internal cavities for thermal diffusivity fillers was proposed to solve the problem of low-grade heat accumulation, which restricts the heat injection efficiency of thermo-activated walls. A dynamic heat transfer model of the MTAW was established., and its performance was compared with two reference walls under typical winter conditions in a cold climate zone. The study examined the effects of the filler cavity inclination angle(θ), cavity geometry ratio(a:b), and thermal conductivity of the filling material(λ_f) on energy-saving potential and economic performance. Results show that incorporating filler cavities and thermal diffusing materials significantly reduces total operational energy consumption and costs. Compared with the reference walls, when the the MTAW filler cavity’s long axis is oriented transversely with an a:b ratio of 1:2, the total operational energy consumption decreases by 2.60% and 14.13%, respectively. Compared with the reference walls, operational costs are reduced by 12.41% and 50.04%, respectively. When the long axis of the filler cavity is inclined toward the room side, heating energy consumption initially decreases and then increases as θ rises, with optimal performance observed at θ_L=60°. Additionally, a:b and λ_f are inversely proportional to both total operational energy consumption and costs. For example, when λ_f is 12λ_c, heating energy consumption and gas operating costs are reduced by up to 3.03% and 34.53%, respectively.

In the context of racing to carbon neutrality, the pipe-embedded building system makes the opaque envelopes gradually regarded as the multi-functional element, which also provides an opportunity for thermal insulation solutions to transform from high to zero-carbon attributes. Based on the re-examination of the heat transfer process of conventional pipe-embedded radiant (CPR) walls, the modular pipe-embedded radiant (MPR) wall integrated with thermal diffusive materials is proposed to enhance the heat transfer capacity of CPR walls in the direction parallel to the wall surface, thereby forming a more stable and continuous invisible thermal barrier layer inside the opaque envelopes. A comprehensive thermal and energy-saving analysis study regarding the influence mechanism of several key factors of MPR walls, e.g., the inclination angle of the filler cavity (θ-value), geometry size of the filler cavity (a:b-value) and thermal conductivity of the filler (λ_f-value), is conducted based on a validated numerical model. Results show that the dynamic thermal behaviors of MPR walls can be significantly improved due to that the radial thermal resistance in the filler cavity of MPR walls can be reduced by 50%, while the maximum extra exterior surface heat loss caused by the optimization measures is only 2.1%. Besides, a better technical effect can be achieved by setting the major axis of the filler cavity towards the room side, where the interior surface heat load/total injected heat first decreases/increases and then increases/decreases with the increase of the θ-value. In particular, the MPR wall with θ_L = 60° can obtain the best performance when other conditions remain the same. Moreover, the performance indicators of MPR walls can be further improved with the increase of the cavity size (a:b-value), while showing a trend of rapid improvement in the λ_f-value range of 2–5λ_C and slow improvement increase in the λ_f-value range of 5–12λ_C. In addition, the improvement effect brought by optimizing the θ-value is more obvious as the a:b-value or λ_f-value increases.