ᐅ Underfloor Heating Heat Load Calculation – Explained Simply

Good day,

I have read many posts on this topic and have so far understood that room-by-room control (RBC) is no longer necessary nowadays, as it reduces the efficiency of the heat pump.

We have a ground-source heat pump with underfloor heating in all rooms.

The goal is to perform a room-specific heating load calculation so that the temperature is properly set once and never adjusted again.

Our general contractor (GC) now argued that while this is basically correct, once people reach their 60s or older and develop different habits regarding room temperatures, it is not so easy to adjust. Therefore, their suggestion is not to optimize for the highest efficiency right now but to maintain some flexibility through RBC.

I think this argument should not be underestimated. However, I suspect that with the "modern" method of a maximally efficient heating system, this might also be possible.

How would you respond to the GC on this?

Thank you very much and best regards

Hamburger2020 schrieb:

So far, I understood that individual room control (IRC) is no longer necessary nowadays because it reduces the efficiency of the heat pump.

That is true if done correctly. However, individual room controls are still required as part of funding programs – although they can be deactivated later or exemptions can be requested (if you manage to do so).

Hamburger2020 schrieb:

The goal is a room-by-room heating load calculation so that the temperature is properly designed once and then never adjusted again.

That should be the standard. But it has nothing to do with the heat pump; it’s about proper heating system design. In that case, a hydraulic balancing aligned with this calculation should also be carried out.

Hamburger2020 schrieb:

Our general contractor argued that this is basically correct, but once it is set, if you develop different heating preferences in the rooms when you are 60+, it is not that easy to change.

That’s nonsense. First, you can’t really control temperatures with individual room controls anyway, since in modern, well-insulated houses all rooms tend to have roughly the same temperature. Second, there is something like a heating curve which can be shifted or adjusted in steepness alongside.

Hamburger2020 schrieb:

Our general contractor argued that this is basically correct, but once it’s set, if you’re over 60 and have different habits regarding room temperature, it’s not so easy to adjust. Therefore, their suggestion is not to aim for the highest efficiency right now, but to keep some flexibility through the ERR.

I believe this argument should not be ignored. However, I suspect that with the "modern" approach of a maximally efficient heating system, it’s also possible.

In addition to the points already mentioned, with the ERR you can really only implement emergency shut-offs. And if the room(s) are not thermally separated from the rest, they will be heated by the surrounding rooms, which only increases their overall heating demand.

In the end, this is a simplistic calculation, assuming the house is occupied continuously. The supposed savings by "turning down" the rooms with the ERR do not materialize. The heating demand of the surrounding rooms increases, shifting consumption elsewhere. Simply put. In reality, of course, it’s all much more complex.

Hello,

thank you very much for the quick responses!

If the heat distributes itself throughout the house anyway, to what extent does it make sense to carry out a room-by-room heating load calculation and to install smaller spacing in some rooms, if the heat will distribute in the end anyway?

What we have planned are electric towel radiators in the bathrooms to quickly raise the temperature there. But installing them with closer spacing in those rooms wouldn’t make a difference, right?

This is about efficient system design. Although the heat spreads, you won’t reach your desired temperatures with a correspondingly low supply temperature. You will need to increase the supply temperature to achieve your target temperature in all rooms, which leads to higher energy consumption.

By the way, an electric towel warmer makes sense because the bathroom usually only receives limited coverage from the underfloor heating. It also consumes more energy, but instead of reducing the heat in all other rooms just to make the bathroom cozy, electric towel warmers are installed. Alternatively, wall heating can be used (essentially underfloor heating embedded in the wall plaster).

Although Tolentino was faster, here is an additional note. The purpose of calculating the heating load for each room is to determine the minimum requirements. It is possible that with a standard installation, the desired temperatures cannot be reached at all. In this case, these rooms may be partially heated by adjacent rooms, but if the neighboring rooms also supply only limited heat, the situation becomes problematic, and significantly higher supply temperatures are needed. Otherwise, you end up sitting in a cold house, and the energy recovery system (ERS) is just decorative.

This is almost always the case with a well-balanced underfloor heating system anyway.