The technical dimensioning of an air curtain often rests on an insufficient basis when it comes to the influence of the building envelope and the ventilation system. The air curtain has a vital connection to both these elements and this has to be taken into account properly in the dimensioning procedure. The goal of the work was to bring new perspectives to such questions as well as to provide certain practical tools for the dimensioning process. This second part of the paper is focusing on thermal aspects. A theoretical approach to determine the thermal loss through the doorway, based on defined jet velocity and temperature profiles is presented. A comparison with empirical results is carried out. A simplified equation for the thermal efficiency of the air curtain is derived. A procedure for the technical dimensioning consisting of 10 steps is presented. The thermal loss through a properly working air curtain is due the turbulence generated entrainment-spill process. The thermal loss is proportional to the thermal loss coefficient and the square root of the jet momentum flux. The jet impact point has a strong effect on the thermal loss. The door dimensions and the neutral pressure level are also major factors influencing the thermal performance of the air curtain. To keep the loss close to the minimum in real conditions where the pressure across the jet is changing, a control for the jet is required. The thermal efficiency as a performance factor for the air curtain can be a misleading concept. (C) 2002 Elsevier Science B.V. All rights reserved.