Two- and Three-Dimensional heat flow Patterns
The method of analysis most commonly practiced today when evaluating the
thermal performance of building spaces, components, and assemblies is based on a
simple, one-dimensional, constant flow model of heat conduction (i.e. the
assumption of parallel heat flow for the calculation of U-values 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
- unforeseeably high energy consumption for heating,
as well as
- damage caused by surface condensation of moisture.
These potentially negative consequences of over-simplification, inherent to
the assumption of one-dimensionality, 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.
Multi-dimensional (i.e. two- and three-dimensional) 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 decision-making process, thus leading to considerably more reliable
Surface moisture due to condensation (typically occurring in such regions as
floor-wall connections, window installations, etc.) as well as mould growth in
humid environments can also be effectively prevented by means of
multi-dimensional evaluation during planning and detail design.
See also: Multidimensional Vapour Diffusion, European standards on
thermal heat bridges