Thermal Bridges Dynamic Simulation And Heat Transfer Coefficient Value For Specific Thermal Bridges

A thermal bridge is a part of the building envelope where the otherwise uniform thermal resistance is significantly changed by: • Full or partial penetration of the building envelope by materials with a different thermal conductivity and/or • A change in thickness of the structure and/or • A difference between internal and external areas, such as occur at wall-floor-ceiling junctions. INTRODUCTION The study of heat transfer in buildings can be achieved by subdividing the structure into wall types (walls, windows, doors, floors and roofs), for which heat losses can be calculated separately. This kind of calculation is normally based on a onedimensional model, i.e. assuming that the walls are homogeneous and are composed of a number of parallel layers for which the heat flow is perpendicular, as shown in Figure 1. The heat transfer can be described for such a model, given some simplifications, by the thermal transmittance of the wall (the U-value). This value gives the heat loss through the building element per unit of inside to outside temperature difference and per unit of surface of the building element: