Abstract
The hydronic thermal barrier (HTB) makes the building envelope gradually regarded as a multifunctional element, which is an opportunity to transform thermal insulation solutions from high to zero-carbon attributes. However, inappropriate design, construction, and operation control may lead to issues like low efficiency and high investment, and even the opposite technical effects. In this paper, a comprehensive uncertainty and variable ranking analysis is numerically conducted to explore the influence mechanism of twelve risk variables on three types and five thermal performance indexes under summer conditions. The uncertainty analysis results showed that the correct application of HTB could significantly reduce the heat gain that needs to be handled by the traditional air-conditioning system and even have the technical effect of auxiliary cooling if the variables are appropriately selected. The comprehensive influences of water temperature, room temperature, charging duration, and thermal conductivity of the HTB layer were in the first 1/3 range. Among them, the first two variables were identified as the two most influential variables, and they had a significant mutual restriction relationship in all other four indexes except for the exterior surface cold loss. The recommended charging duration was not less than eight hours in practical application, and the HTB layer with a higher thermal conductivity value but less than 3.3 W/(m·℃) was suggested. Besides, the climate zone was no longer the most influential variable affecting the mean radiant temperature of the interior surface due to the combined effects of HTB and static thermal insulation measures. In addition, pipe spacing should preferably be selected between 100 and 250 mm to help form a continuous thermal buffer zone inside the building envelope.
