A thermo-active foundation system can be a cost-effective technology to utilize ground thermal energy to heat and cool buildings. Indeed, thermo-active foundations, also known as thermal piles, integrate heat exchangers with the foundation elements and thus eliminate the need of drilling deep boreholes typically required by the conventional ground source heat pumps. In order to properly design thermo-active foundation systems, their thermal performance under various operating and climatic conditions are evaluated as part of this study using detailed modeling and simulation analyses. In particular, a transient three-dimensional finite difference numerical model has been developed and validated to analyze thermal performances of thermo-active foundations. The numerical model is then used to assess the impact of design parameters such as foundation depth, shank space, fluid flow rate, and the number of loops on the effectiveness of thermal piles to exchange heat between the building and the ground. Moreover, thermal response factors have been developed to integrate the performance of thermo-active foundations within detailed whole-building simulation programs. In this study, response factors specific to thermo-active foundations are implemented into EnergyPlus to investigate the impact of various design and operating conditions. The results from the detailed simulation analysis are then used to develop a set of guidelines to properly design thermo-active foundation to meet heating and cooling loads of commercial buildings.The design guidelines define the required number of thermal piles needed heating and cooling loads for prototypical office buildings in selected US climatic zones. In particular, charts have been developed to help determine the number of thermal piles needed depending on heating and cooling loads, heat pump size, foundation depth, and climate
