The valid standard ISO 10211 do not consider this possibility, and ignores this thermal flux which may increase LTT by 15% (see following publication with DOI: 10.13140/2.1.4451.8726).
In my opinion, inclusion of this heat flow is physically and technically reasoned, because the floor heating is often an integral part of the structure (floor, ceiling, etc.). This approach would however lead to pressure on the more precise solution of thermal bridges in such structures.
Would it be useful?
Conference Paper Vliv podlahového vytápění na tepelné mosty
Yes it would be useful. You are right - inclusion of this heat flow is physically and technically reasoned.
This will have a significant impact, if we do not take into account the structural detail for example - around the peripheral wall edge missing "strip" and similar... (in connection of the peripheral wall and floor). This impact should also be taken into account in the calculation - and perhaps even at today's effort to minimize heat loss and gets the category of "passive" houses.
I think the ISO 10211 might be used to include radiant floor heating by splitting up the problem in two seperate problems where the radiant slab is used as a fixed temperature boundary layer. Hower, introducing the floor heating makes it a transient problem where the hardest problem might be defining the average temperature of the radiant slab.
Thank you for your answer Ruben. Considering steady stay conditions at floor heating (so as we are considering the same at building structure according the ISO 10211), we can move away from the transient problems. Then the effect of the floor heating slab could be defined at least in a two ways:
1) by – as you mentioned – average temperature of the slab derived, for example, from the theory of heat conduction in the fin with insulated end – a simplified procedure;
2) by the numerical simulation of heat transfer – a more detailed procedure;
However, in both cases, there becomes necessary to deal with more LTT due to the addition at least one more boundary condition, which get the whole issue more complicated.
My question was directed to the next:
If we would follow these steps, do you think that we get sufficient benefit justifying this more complex calculations?
Hello,
I think it is feasible to include floor heating devices in calculations of thermal bridges, given the fact that we can assess different questions:
- In assumption of winter season and "used" spaces, the heater would presumably run anyhow, therefore mitigating the effect of the thermal bridge (this is anyhow happening in reality).
- For reasons of comparison on the performance of different constructions it needs to be clarified which conditions are assumed.
Regarding the issue with the third boundary condition - in the software package AnTherm there is an elegant way around, as heating pipes are drafted to the model and the heat energy (in W / m³) is stated.
I also agree that it has to be carefully thought about the purpose of a thermal bridge model in regard wheather a steady-state or a transient simulation is applicable... (this it the old - "worst conditions"-steady state versus "reality hits"-transient simulation).
Best wishes to Brno :)
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