
Two and ThreeDimensional heat flow PatternsThe method of analysis most commonly practiced today when evaluating the thermal performance of building spaces, components, and assemblies is based on a simple, onedimensional, constant flow model of heat conduction (i.e. the assumption of parallel heat flow for the calculation of Uvalues and areas). Such an assumption often leads not only to disappointing results in the thermal performance of realized construction projects, but also to costly consequences due to
These potentially negative consequences of oversimplification, inherent to the assumption of onedimensionality, are becoming increasingly critical in today's trend towards highly insulated building structures. If the effects of thermal bridges are neglected, drastic errors in estimating heating requirements are bound to result, particularly when assessing energy efficient buildings. Multidimensional (i.e. two and threedimensional) evaluations of thermally critical regions within a building assembly, especially those with thermal heat bridges, during early design phases can provide valuable preliminary information to support the decisionmaking process, thus leading to considerably more reliable design results. Surface moisture due to condensation (typically occurring in such regions as floorwall connections, window installations, etc.) as well as mould growth in humid environments can also be effectively prevented by means of multidimensional evaluation during planning and detail design. See also: Multidimensional Vapour Diffusion, European standards on thermal heat bridges 
