The European standard EN15450 states that the Coefficient of Performance (COP) target range for a Ground Source Heat Pump (GSHP) installation should lie within the range of 3.5 to 4.5; when used for heating a building, and a typical Air-Source Heat Pump (ASHP) has a COP of 2.0 to 3.0 at the beginning of the heating season and then decrease gradually as the ambient air becomes cooler, whereas a typical GSHP is in the range of 3.5 –4.0, also at the beginning of the heating season and then decrease gradually as heat is drawn from the ground.Therefore in the middle of winter, the COP drops significantly. In addition soil presents certain difficulties, due to the high cost of drilling to position coils in the ground compare to air source, although frost formation on the evaporator in winter limits also limit the use of air source. In order to wide spread those technologies in Low Carbon Houses is crucial to overcome those issues. This book aims to investigate those issues. It looks at modelling, lab testing and field trial evaluation of novel heat pump technology to reduce freezing effects around the bore hole and to maintain high COPs from beginning to the end of the heating season.