A design method for insulation distribution to achieve year-round energy-efficient operation of double-layer pipe-embedded wall

Double-layer pipe-embedded walls (DPEWs) offer considerable potential for reducing space heating and cooling energy consumption. Optimizing the thickness distribution between the inner and outer insulation can enhance their performance. To achieve year-round efficient operation of DPEWs, this study proposes a design method for optimizing insulation distribution under given insulation locations and total thickness. The proposed method determines optimal outer insulation thickness ranges for representative working conditions and selects the design thickness based on their intersection. If a common range exists across all working conditions, its maximum value is adopted as the design thickness to prevent freezing; otherwise, the common range derived from important working conditions that constitute a significant proportion of the total duration is adopted. A case study is conducted in six cities using a DPEW system combined with an air source heat pump and ground heat exchangers. The results show that: (1) for each working condition, an optimal outer insulation thickness range maintains energy consumption within a small deviation above the minimum; (2) a common optimal outer thickness insulation range can be determined across either all working conditions or important working conditions; and (3) the proposed method demonstrates good applicability in diverse climate zones. This study provides guidance for DPEW design and contributes to improved building energy efficiency.