
IntroductionThe program AnTherm® is used to calculate stationary (steady state, time
independent) and dynamic (transient in time periodically) distribution of temperature and heat flux within building
construction, especially to determine surface temperatures and thermal coupling
coefficients. Is is also used to determine vapour diffusion in building
constructions. Extensive visualization support and extend the analysis. In that simple cases in which the temperature within the building component is only dependant on one location coordinate, i.e. in the case of one dimensional heat transport, there is no need for specialized computer programs; the calculations can be easily completed by using well known, simple formulas. If the temperature distribution depends on two Cartesian space coordinates then we have to do with two dimensional heat transport and linear thermal bridges. The general, three dimensional case of heat transport shall be considered if the temperatures depend from three space coordinates. The program AnTherm® allows calculation of temperature distribution for the two as well as for three dimensional heat transfer. The program AnTherm® has been developed for model calculation of such building components of which the boundaries are parallel to coordinate planes of the orthogonal Cartesian coordinate system. Thanks to such limitation to orthogonal network the practical input can be quickly executed. Any construction set up of interconnected or overlapping ashlars and arbitrary materials can be simulated. The limitation to orthogonal structures allows relatively finely grained calculation of temperature distribution even on typical personal computer. Since the temperatures are calculated not only at cell centres, but also at sides, edges and corners of each cell, the simulation of say 20.000 cells provides 80.000 node temperatures in two dimension or even 160.000 nodes in three dimension very quickly. For 1.000.000 calculated cell there will be more than 8.000.000 temperature nodes calculated in 3D! On one hand the temperature distribution depends on the geometry and physical properties of the component and, on the other, from air temperatures within spaces attached to the component (boundary conditions). There can be more than only two spaces attached to the component  this is the additional and major difference of two or three dimensional cases compared to one dimensional calculation. Computational description of vapour diffusion in building constructions can provide valuable hints for answering the questions if there is a risk of, potentially destructive, vapour condensation within the construction or not. The implementation provided in AnTherm shall be mainly used for answering the question if, and if so where within the construction, by given boundary conditions (air temperature and relative air humidity) moisture is produced. The distinctive feature of AnTherm® is that the relatively laborious calculation of the temperature distribution, which is provisioned by solving large system of linear equations, need not be repeated for each different set of boundary conditions. Anticipating that need AnTherm determines so called "base solution" during the calculation only once. These base solutions are then superposed to temperature distribution under requested boundary conditions leading to significant reduction of computational time when several variants of boundary conditions are of interest. With regard to theoretical background reference should be made to the book ”WÄRMEBRÜCKEN” (Heindl, Kreˇc, Panzhauser, Sigmund; SpringerVerlag WienNew York). • See also: Tutorials and Cookbooks, Primary Concepts, Theoretical background 
