Heat demand calculation according to DIN 12831

Hello everyone,

we are currently building a house and are actually quite satisfied with the construction company. I have already asked here a few times regarding the heating, etc. In the contract, I had noted that a heat demand calculation according to DIN 12831 must be carried out.

Now, after the sample selection, I have received a calculation according to DIN 4701 (Energy Saving Ordinance 2009).

I still consider myself on the safe side - since everything is recorded in writing. What surprises me now is - shouldn't the heat demand calculation be done soon, and is the construction company making things difficult for themselves?

We have decided in advance on a geothermal heat pump with brine + heat recovery in the KFW 55 house. Suppose this is not sufficient - what would happen then? (So it is clear that it would either be cold or expensive.) Could it happen now that we have to pay a lot more if the heating is undersized? Or am I worrying too much?

Many greetings and best thanks,

Hello,

...In the contract I had it recorded that a heat demand calculation according to DIN 12831 must be carried out.

Here one has to clarify existing deficits, whose cause (in the past) unfortunately lay in a certain incompetence of the standards committees regarding the binding SI units
This has meanwhile been corrected as a result of objections from experts
Heat demand => Energy: unit kWh
Power (heating load according to 12831) => Power: unit kW
This is probably about the normative heating load (kW). This is regulated EU-wide in connection with the national annexes and must only be created according to 12831 (in Germany a detailed procedure)!

...Now I have - after the sampling - received a calculation according to DIN 4701 (Energy Saving Ordinance 2009)

If 12831 was sensibly requested, then 12831 must also be included (after all part of the contract!)
Deriving sizing bases for heating systems from the Energy Saving Ordinance is not permissible! For this, please read the fine print in the proof!

...I still consider myself on the safe side - since everything is recorded in writing. What surprises me now is - shouldn’t the heat demand calculation be done soon and is the construction company making things difficult for themselves?

Construction companies build, MEP and efficient system technology is rather a foreign word for most.

...We decided in advance for a geothermal heat pump brine + heat recovery in the KfW 55 house.

An economically unfortunate constellation. The jump from EH 70 to 55 involves considerable investment (mostly H´T value). The significant additional effort for the building envelope usually bears no relation to the benefit, since in connection with a brine heat pump only a fraction is actually effective. Cost-intensive here, among other things, is the source development, unless considerable in-house work shares can be made effective (trench collector).

...Assuming this would now not be sufficient - what would happen then?

The desired room temperatures will not be achieved.

...Or am I worrying too much?

One usually only builds once - everything should be right! Hopefully the general contractor, regarding the MEP, is capable of realizing a coherent overall concept, otherwise probably a money pit.

Best regards

Thank you for the reply. Well, the upgrade to the brine heat pump was rather my idea to do something for the environment and to rely on an alternative heating system. Aware that the initial costs are higher, but the operating costs are low.

The extra cost for KFW 55 (more like 40) + underfloor heating + the heating technology was okay! (for me) We didn’t want a passive house.

If 12831 was sensibly required, then 12831 must also be included (after all, part of the contract!)

Same here – so I understand that the sample selection is still to be waited for, since we redesigned the windows, etc. How does the professional house builder actually do it? Does he plan the house around the heating?

Well, we’ll see. It’s still 2 weeks until the foundation slab.

Deriving sizing fundamentals for heating systems from the Energy Saving Ordinance is not permitted! For this, read the fine print in the proof!

Then the sentence in the calculation: heat recovery is therefore sufficient for heating, is actually not even lawful? Well, good thing I have legal expenses insurance.

.. Aware that the initial costs are higher, but in return the operating costs are low.

With a SWP, a relatively high proportion of environmental energy can be utilized with sensible design of the source. Therefore, from an economic point of view, the requirements for the building envelope are lower. Or vice versa, those who invest heavily in the building envelope should forgo the high effort of source development of a SWP!

.. How does the professional home builder actually do it? Does he plan the house around the heating?

What is a professional home builder? Certainly not a general contractor. Most often it is builders or traders. The complex connection between the building structure and plant technology is usually missing here. Therefore, for example, KfW 70 is also sold with AWP.

... Well, good thing I have legal expenses insurance

A big misconception! Construction matters are not insured here, guess why!

Then I am curious to see what heating costs await me, after all, the loan was 200 euros cheaper per month than planned - or the stove must be burning all the electricity bills.

So I better start putting pressure on the company now and demand my calculation.

When reviewing my documents, I was then surprised by myself...

I had not contractually agreed that we would receive a heating load calculation. It says: "Planning according to DIN EN 12831" - that's actually even better.

I have now simply asked the construction company for the planning documents, they should be on site.