Since buildings make a major contribution to the distribution of total energy, it is essential to take into account their functionality and the repercussions this has. Passive solar technology is a vital part of contemporary architecture, and the Trombe wall, as one of its principles, certainly stands out from the others. The new transparent Trombe wall (T-T-W) can receive solar intensity from all four sides. We developed the addition of parallel slats of transparent insulating material (TIM-PS) in the newly designed T-T-W with the help of a numerical study using CFD simulation. Taking the actual climatic conditions of a winter solstice day with a Mediterranean climate, the optimal design of a T-T-W was investigated. The use of perpendicular TIM-PS can eliminate convective heat loss through the south glass wall, increasing thermal efficiency from less than 5% to over 19% at 17H.The operating time when the TIM-PS is placed increases from 9 h for the conventional glass wall to 11 h for the perpendicular glass wall equipped with TIM-PS. This high-performance design ensures high thermal comfort, even at the lowest levels of sunlight, guaranteeing good thermal comfort in the early hours of the night. Nevertheless, adjusting the slats on the south-facing glass wall would not reduce the amount of incident radiation, as the slat material, polymethyl methacrylate (PMMA), is highly transmissive (92%).