Heating proof: Heat load calculation according to DIN 12831 or DIN 4708?

A question about that. If I want to have the sizing of my heating system planned sensibly - as far as I hopefully understand - do I need a proper energy consultant / TGA?..

Less so an energy consultant, a TGA planner is responsible for this. Sometimes you find both roles combined in one person!

....On what basis does he calculate then? Do I tell him the demand from my last utility bills, how often I take a bath, and how warm I like it in my rooms?

Not for the heating operation, because a new building has completely different demand requirements/necessities than the previous rental apartment!
In the planning, the desired room temperatures are taken into account! Form sheet V DIN 12831.
For hot water, the usage requirements are also considered. Surely there is a difference between a weekly bath and the fact that a football team comes to shower daily.
Hot water preparation must be planned just as carefully as the heating operation.
Recently, builders often face shortages in hot water supply!
In the past, hot water was handled incidentally with the same heat generator, which was usually unproblematic due to the high heating loads. Meanwhile, times have changed significantly thanks to the Energy Saving Ordinance. For well to very well insulated buildings, it can sometimes make sense to separate heat generation for heating operation and hot water! A very typical case: Passive House according to PHPP!
I currently have two such cases under review. Aside from the completely excessive consumption costs, the builders in winter can choose whether they want hot water or their desired room temperatures.

Best regards.

Hi,

to me, it all sounds somewhat confusing. It sounds as if the heat proof is not worth the paper..
What is the proof actually good for – does it contain usable statements/indications regarding expected heating costs etc. (the granularity "very high heating costs/sqm, low heating costs/sqm" would be enough)?
What I’m actually just trying to do is check whether what I eventually receive corresponds to Kfw70 or if it has been "beautified". Impossible?

Of course, one would then also have to check whether what is stated in the document is actually built that way, but that is phase 2.

Regards,
Lacos

Hello,

.... That sounds as if the heat verification is not worth the paper..

That is not entirely correct. Both the Energy Saving Ordinance / KFW and EEWG verifications have their justification. However, they can only be used and applied as intended or prescribed by the legislator.
See above!

...What is the verification good for - ....

=> see above!

....does it contain usable statements/indications regarding expected heating costs etc. (granularity like "very high heating costs/sqm, low heating costs/sqm" is sufficient)?..

Qualitatively yes. However, the objectives are different. The legislator focuses on primary energy, but the private builder has to pay for final energy!
Since every construction project is significantly individual, a qualitative comparability would hardly be possible. With the Energy Saving Ordinance / KfW, standardization of certain boundary parameters was introduced to create this qualitative comparability. What is actually needed / consumed later cannot be represented here! Therefore, I always calculate to my clients beforehand what costs they have to actually expect later! Since this happens in the preliminary planning phase, any necessary changes can still be easily implemented without much effort. Sometimes it is small things with little effort, but great effect.

...all I am actually trying to do is to check whether what I get later corresponds to KFW70 or if it was "cooked" (beautified). Impossible?

The Energy Saving Ordinance / KfW verifications are to be understood as preliminary, overarching planning.
Example: If 35°C flow temperature, night setback, no hot water circulation, insulation of pipes according to Energy Saving Ordinance etc. are specified in the verification, and these are not adhered to later in detailed planning or execution, the intended energetic standard of the building and system is often violated. That would be an initial "beautification".
Next example:
In new construction verifications, the flat surcharge for the thermal bridges of 0.05 is mostly used. However, this presupposes that all thermal bridges are executed at least according to DIN 4108 Part 2. Here an equivalence verification is required!
Looking at practical execution, there is often little of this left!

Best regards

NB: Why builders do not want to know beforehand what consumption costs they will have to expect later, yet sign contracts in large amounts, remains a mystery to me to this day!

Hi everyone, hello Euro,

I noticed in the thermal protection verification that an indoor setpoint temperature of 19 degrees is assumed.
Is this a common calculation basis?

Location "Germany", 50°00' northern latitude, Region 0, Ta (annual average) = 8.9°C
Indoor setpoint temperature = 19.0 °C

Regards,
Lacos

Hello,

....Is this a common calculation basis?..

Yes, since it is standardized and normalized, alongside the other energy saving regulation parameters. Therefore, energy saving regulation/KfW certificates have absolutely nothing to do with the actual conditions!!!
For example, hot water:
According to the energy saving regulation/KfW, the demand is "preset" to 12.5 kWh/m²a x An. An is a purely fictitious area that has absolutely nothing to do with the actual heated living area!
The actual hot water demand depends on the number of persons, the supply temperature, user habits...
Example: An = 200 m² hot water demand according to energy saving regulation => 2500 kWh/a.
Now the building can be used by 2 persons or 8. Under otherwise identical conditions, for example, the following actual demand (not consumption!) would result:
2 persons: => 1360 kWh/a
8 persons: => 5440 kWh/a
What use is the energy saving regulation/KfW certificate then? None

Heating: An identical building can be located on the Zugspitze or at the Lower Rhine! The system room temperature (RT) is geometrically weighted according to heating loads 24°C for one family and 21°C for the other!
One operates the heating ad libitum, the other heats continuously!
What use is the energy saving regulation/KfW certificate then? None

To determine the actual conditions/necessities, at best the component geometry and definition of the building envelope can be used from energy saving regulation/KfW certificates – nothing more!

Regards