Heating for KfW70 multi-family house - the total confusion

Hello forum!

We finally want to build. The building plot is purchased, the architect’s plans are finished, the offers are being collected.

So far, so good – if it weren’t for that one point that all 5 providers answer inconsistently:
Everyone has at least one opinion on the topic of heating. These opinions contradict each other drastically, so that we – ignorant laypeople – now know nothing at all. We will soon resort to rolling dice to answer this question.

- The energy consultant says that in such a well-insulated house with heat recovery, no heating is needed for room air; for hot water, a small boiler is enough
- Provider A says that an air-source heat pump for this huge house is expensive and not economical.
- Provider B recommends pellet heating
- Provider C recommends a gas condensing boiler solution coupled with solar thermal
- Provider D recommends geothermal energy, which A and E advise against because the investment in the risky deep drilling will only pay off in 120 years.
- The keyword “mini power plant” has also come up in one place but was immediately criticized elsewhere!

The house:
Living space is spread over 2.5 floors with 130 sqm each,
additionally, 70 sqm in the basement will be used as practice/office space.
The ceiling height is effectively 2.75 m.

A ventilation system with heat recovery is firmly planned, as well as underfloor heating.
We would like photovoltaics and solar thermal if it makes economic sense.

With online “calculators” I have
a) no good feeling
b) no way to factor in the heat recovery
but the values are roughly heat demand 7000 kWh/a and heating load of 17.84 kW.

What do you recommend? What experiences have you had?

Regards,
Micha

Hello,

- The energy consultant says, in a house that is so well insulated ...

Meaning?

These details are needed to be able to assess statements A - E; although I am already fairly certain - unless you are currently building a passive house - that I would shoot the "energy consultant" to the moon ;)

Kind regards

Hello,

....b) no possibility to include the heat recovery

Who does not have this possibility?

....but the values are roughly heat demand 7000 kWh/a and heating load of 17.84 kW.

Who has calculated, how?

....What do you recommend?

Hire an independent planner!

Best regards

These details are necessary in order to be able to evaluate statements A - E ...

Since the house is not yet built and we also have no points of comparison, we are exactly facing this problem, namely that we cannot evaluate these contradictory statements. Everyone talks their nonsense and everyone argues in favor of their own statement. As a layperson, after every consultation you feel dumber than before!

Who does not have this possibility?

_I_ do not have this possibility with the calculators found on the internet (discovered). If there is a reasonable tool known to you, I would be very glad to be informed about it.

Who has calculated how?

Also _I_, using those very calculators on the internet – which I wouldn't trust with two cents.

Hire an independent planner!

Yes, that’s probably what it comes down to! Are these the TGA planners? Is there a directory for these independent planners? Or a certificate/seal/association that one can trust?

It is simply shocking that here, in a free, public forum, one gets a more meaningful statement than from the people who pretend to have swallowed the wisdom of house construction with a spoon by profession.

Thanks for now

Hello Micha,

_I_ have not (discovered) this option with the computers found on the internet. If there is a reasonable tool known to you, I would be highly pleased to be informed about it.(...)

Direct links are not desired in this forum, but try googling, for example by searching for "u-wert" and "wärmebedarf."

In my opinion, you cannot perform a heating load calculation there, but a detailed heat demand calculation, which also includes ventilation losses with/without heat recovery.

Regards
Olaf

......In my opinion, you cannot perform a heating load calculation there, but a detailed heat demand calculation that also takes into account ventilation losses with/without heat recovery.

I can only strongly warn against such "rules of thumb"! It may be suitable for calculating a U-value. Everything else is unreliable and carries significant risks. Anyone who absolutely wants to save on a necessarily precise planning/dimensioning must know what they are getting into. There are more suitable areas where you can take action yourself without causing lasting damage.

Best regards