Is the building technology okay?

Hello dear readers,

we are specifically planning for our new build next year. Key data: single-family house, approx. 130 sqm, basement.

Bien-Zenker has come into closer consideration. The price/performance ratio seems okay to us, we like the floor plan, and it is a large home builder as well.

For heating, we were proposed a brine-water heat pump (we wanted underfloor heating), underfloor heating, and controlled residential ventilation including heat recovery.

Our budget is also limited, and we would have the so-called Efficiency House 55 thermal wall with a heat transfer coefficient of U=0.142 W/sqmK.

Overall, the house would have the Efficiency House 70 standard.

I am not a professional, but compared to other manufacturers, this value is in the mid-range. The "standard wall" from Kampa, for example, would be better.

What do you think overall about this offer regarding the home technology?

Does the heat pump pay off over the years compared to the standard gas condensing boiler?

Many thanks from a newcomer for your support/answers.

Doesn't anyone have anything to say about this? Another question that arises for me is whether the hot water supply can also be provided without problems via the heat pump, since the temperature of about 60 degrees is significantly higher than the flow temperature of the underfloor heating. Would solar panels on the roof possibly make sense for the summer? Thank you very much for your opinions...

Does no one have anything to say about this?

You can say a lot, but the question is how reliably such issues can be resolved in a forum, since considerable effort is required if it is really supposed to be effective. Heat pumps can very well be an alternative to gas condensing boilers, but this requires compliance with specific conditions. Whether in the present case a brine heat pump with the additional costs of source development is necessary would also have to be clarified in advance. After all, a heat pump basically offers the possibility to do without a less efficient solar thermal system. ;) I have just prepared an expert report on such a solar thermal system with the result that the energy yield was only very slightly higher compared to the additional effort of auxiliary energy. So an investment ruin!

...Another question that arises for me is whether the hot water supply can also be provided easily via the heat pump, since the temperature of about 60 is indeed significantly higher than the flow temperature of the underfloor heating.

A heat pump is more efficient the smaller the temperature difference between source and consumer is. Hot water preparation is easily possible with a heat pump, but temperatures of 60 degrees are a yearly performance factor killer, depending on how high the share of hot water preparation in the total annual final energy demand is.

...Does solar on the roof possibly make sense in the summer?

Primarily in terms of primary energy, yes; economically usually not!

Best regards

@ €uro,

thank you first of all for the contribution.

The framework conditions with a KFW70 standard and underfloor heating would be fine according to my knowledge. A controlled ventilation with heat recovery would also avoid ventilation losses. What exact figures would be necessary for a somewhat serious calculation? Quick question: solar thermal system? Solar system on the roof?

Regarding the heat pump for hot water: which solution would be sensible here? An electric boiler in the bathroom and under the sinks in the bathroom/WC/kitchen? I have assumed 60 degrees because of legionella. Theoretically, the temperature could be 10-15 degrees lower to have a pleasant shower experience.

I was thinking of the solar system on the roof to prepare hot water almost exclusively in summer. But according to your statements, that wouldn’t make much economic sense.

I was simply generally interested in whether, when using a heat pump, the hot water preparation can generally be included without thereby eroding the advantage compared to a gas condensing boiler, so that a heat pump does not pay off after maybe 10 years but possibly never. Economically speaking.

Best regards...

... What exact numbers would be necessary for a somewhat serious calculation?

Actually all regarding the building structure, the climate location, and the user behavior. Calculated are: air volumes (if controlled residential ventilation is desired or required), design heating load, room heating loads, heating surfaces, and piping network. Among other things, the results are used to calculate the actual energy demand for heating and hot water. These in turn influence the choice of the heat generator (Wärmeerzeuger).

...Short question: Solar thermal system?

Solar Thermal Apparatus, as opposed to photovoltaics.

.. which solution would be sensible here?

Usually hot water centrally with the same heat generator that also supplies the heating.

...An electric boiler in the bathroom and under the sinks in bathroom/WC/kitchen?

That would be direct electric and hardly sensible.

....Theoretically, the temperature could be 10-15 degrees lower to have a nice shower experience.

Draw-off temperatures 45...50 degrees.

...I was generally just interested whether, when using a heat pump, hot water preparation can generally be done as well, ....

If the system is exactly planned/calculated, that is absolutely no problem.

v.g.

Thank you first of all for the explanations :)
So generally, the solution for a KFW70 building is fine if the system is properly calculated/dimensioned. That’s what I have gathered now. Would you also tend towards the solution with the brine heat pump or still stick with a gas condensing boiler system (also with underfloor heating and controlled ventilation with heat recovery)?
Of course, I’m not calculating in the short term here, but in about 10 years, the balance should at least be "zero," meaning the higher investment costs should have paid off and the system should then run "with profit" compared to the gas solution.
Regarding the hot water temperature (tap temperature). Is there not a risk of Legionella formation at 45 - 50 degrees? I always have these 60 degrees in mind.
One more important question: heating in the basement. The consultant said that underfloor heating should be planned right away for the designated basement rooms. What do you think about that? How should I properly heat a basement that will be used as a hobby room (model railway) for the foreseeable future? The temperature shouldn’t need to exceed 18 degrees much even in winter. Ventilation would then be done through the basement windows.
Best regards...