Comparison of performance of simulation models for floor heating

This paper describes the comparison of performance of simulation models for floor heating with different level of detail in the modelling process. The models are compared in an otherwise identical simulation model containing room model, walls, windows, ceiling and ventilation system. By exchanging only the floor construction, the differences can be directly compared.

In this comparison, a two-dimensional model of a slab-on-grade floor including foundation is used as reference. The other models include a one-dimensional model and a thermal network model including the linear thermal transmittance of the foundation. The results from the comparison show that there are large differences in both heat loss to the ground, energy consumption and temperature distribution in the room.

Differences of nearly a factor two are found for the heat loss to the ground, mainly due to the inclusion or omission of the foundation. The result can be also be found in the energy consumption of the building, since up to half the energy consumption is lost through the ground. Looking at the different implementations it is also found, that including a 1m ground volume below the floor construction under a one-dimensional model does not alter the results.

Further, the differences between a hydronic and electrical inclusion of the floor heating pipe can be seen to affect the results. The main differences are found in the fact that the heat supply from the hydronic pipe depends on the temperature of the surrounding floor construction, which is not the case for an electrical (or heat flux) inclusion of the pipe.

Finally it has been found, that a simplified lumped resistance/capacitance model can adequately model a floor construction with floor heating and foundation when compared to a two-dimensional model of a slab-on-grade floor.