Solar with heating support

The solar system is actually less about really heating and more about just getting approval for the gas condensing boiler

That's right!

No and no, both totally uneconomical... does not pay off or only with difficulty after about 30 years and by then a replacement is probably due long ago

And as a moderator, I take the liberty to simply claim that many houses themselves are uneconomical – more expensive than renting if built oversized, and when the house is paid off, everything is outdated and a new loan covers the repairs and modernizations... so why make such a fuss about the amortization of the heating system?

Have a nice weekend!

You are also right: From 2016 onwards, the combination will be discontinued anyway.

Hello Thorsten, hello Andreas,
in connection with a decentralized ventilation system with heat recovery, the combination of gas and solar will still be possible WITHOUT exorbitant insulation of the exterior wall under the Energy Saving Ordinance 2016. Town & Country gets it approved with the help of the ventilation with 24 cm aerated concrete without ETICS, 4 sqm solar thermal.

Michael

Good evening Michael,

Town & Country gets approval for this with the help of ventilation on 24cm aerated concrete without ETICS, 4sqm solar thermal

Well then, let's wait and see if your statement from 2016 can also be implemented that way

Rhenish greetings

We are building a Kfw 70 house next year according to the 2014 Energy Saving Ordinance. Planned are 36er Poroton, gas boiler + solar & decentralized ventilation + heat recovery. I would like to do without solar; is there an economically sensible option for our planned house, or would everything else (additional insulation) only become more expensive?

I am not an expert in the Energy Saving Ordinance 2014.

However, I believe that you must have a certain share of renewable energies. Regardless of whether the calculation of the primary energy consumption already shows that there is sufficient insulation in the house.

This share of renewable energies is generally not achieved by installing a gas boiler without using thermal solar. That is why our little house has such a thermal solar system.

Whether the installation of a photovoltaic system or a water-bearing fireplace can help here, I cannot say. There are certainly experts for that....who can answer this.

Direct neighbors have built a similar house to ours (size, KFW70) and could do without thermal solar because they plan a water-bearing fireplace and also an air-to-water heat pump as heating type. The air-to-water heat pump is accounted for quite differently in the calculations. I am not a fan of this air-to-water heat pump. However, you then save the costs for thermal solar (a few thousand euros), presumably a 150-liter water tank is sufficient (a few hundred euros less), and the installation is simplified. In addition, the costs for the gas connection (depending on the municipality about 2,000 euros) are eliminated, so that the additional costs for the air-to-water heat pump can at least be partly offset.

Best regards Thorsten

Well, let's wait and see if your statement from 2016 can also be implemented that way

How do you mean that, Bauexperte? Why should the GU include this solution in the construction contract and later everything gets rejected by the building authority? That would render the entire construction contract void – and that surely cannot be in the GU’s interest? Or have I overlooked something legal?

Another approach to the question of whether solar thermal energy pays off:

If I need 80 liters of water (2 people shower daily) heated by 35° using geothermal energy (from 5 to 40), I roughly calculate needing 3.5 kWh. Assuming that this energy (including the additional energy required for losses in the buffer storage) can be provided exclusively by the boiler for 8 months, it saves me 840 kWh per year. With gas at 80% efficiency of the gas boiler, I would need about 1100 kWh or approximately 170 liters of gas, which is about just under 55 euros. With an air-water heat pump and an annual performance factor of 3.0, that’s approximately 370 kWh or just under 80 euros.

If the thermal system could unrealistically heat the required hot water on all 365 days of the year, the savings would be just over 80 euros (gas) or just under 120 euros (electricity). Conclusion: Even if there were no capital costs, amortization would be far beyond the economically sensible range.

However, this calculation shifts significantly in favor of solar thermal if I assume that full baths are often taken in high summer, because then the 4 sqm of solar surface can deliver much more energy than the 3.5 kWh assumed above plus buffer losses. Realistically, the calculation tends to shift against solar thermal because the thermal system cannot provide the required energy 100% on all days of the year.

Just my approach to the matter.