Thermosyphons have been used to stabilise ground in permafrost areas since the 60's. On-grade foundations over ice rich permafrost require insulation below the floor to retard heat flow and a cooling system below the insulation to prevent thermal degradation of the underlying permafrost. Heat transfer in the ground and at thermosyphon installations are explained and discussed in this report. Further, methods for designing thermosyphon installations at buildings and roadways are described. Illustrated, as examples, are the case with a varying surface temperature, a roadway and a cross-country ski track.