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.