This paper discusses theDesign/Data Manual for Ground-Coupled Heat Pumpsdeveloped during ASHRAE Research Project RP-366 under the sponsorship of ASHRAE 's TC 9.4 and 6.9 Technical Committees. The manual, directed to the practicing design engineer, was not intended to develop a specific design procedure. Rather, it is a report on the state of the art in the groundcoupled industry. The manual also attempts to fill gaps in available knowledge about soils, materials, and techniques for sizing and installing the systems.This paper summarizes the information in the manual and discusses some of the areas where additional information may need to be developed. Some practical design methodologies are reviewed.Units: Dual