ᐅ Solar Heating Support

andimann schrieb:
The solar system is actually less about really heating and more about getting the gas condensing boiler approved

Exactly!

Mycraft schrieb:
No and no, both are completely uneconomical... they don’t pay off or only barely after about 30 years, and by then a replacement is probably already due

As a moderator, I’ll take the liberty to suggest that many houses themselves are uneconomical—more expensive than renting if built oversized, and once the mortgage is paid off, everything is outdated and a new loan is needed to cover repairs and modernizations... so why make such a big deal about the payback period of the heating system?

Have a great weekend!

T21150 schrieb:
You are also right: The combination will no longer be allowed starting in 2016.

Hello Thorsten, hello Andreas,
in combination with a decentralized ventilation system with heat recovery, the combination of gas and solar heating without extreme exterior wall insulation will still be possible under the 2016 Energy Saving Ordinance (EnEV). Town & Country is getting approval for this with the help of ventilation, using 24 cm (9.5 inches) aerated concrete without external thermal insulation composite system (ETICS / EIFS), and 4 m² (43 sq ft) of solar thermal panels.

Michael

Good evening Michael,

ölschlamm schrieb:

Town & Country gets approval with the help of ventilation using 24cm (9.5 inches) aerated concrete blocks without external thermal insulation composite system (ETICS), 4sqm (43 sq ft) solar thermal

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

Regards, Bauexperte

Next year, we are building a KfW 70 house according to the 2014 Energy Saving Ordinance. The plan includes 36cm (14 inches) Poroton bricks, a gas boiler plus solar panels, and a decentralized ventilation system with heat recovery.
I would like to do without solar energy. Is there a cost-effective alternative for our planned house, or would any other option (such as additional insulation) only lead to higher expenses?

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

However, I understand that you need to have a certain proportion of renewable energy, regardless of whether the calculation of primary energy consumption already shows that the house has sufficient insulation.

This share of renewable energy is generally not achieved when installing a gas boiler without using thermal solar energy. That is why our house has a thermal solar system.

Whether the installation of a photovoltaic system or a water-circulating wood stove can help here, I cannot say. Surely there are experts who can answer that.

Direct neighbors built a similar house to ours (size, KfW70 standard) and were able to do without thermal solar, as they plan to use a water-circulating wood stove and also an air-to-water heat pump for heating. The air-to-water heat pump is accounted for differently in the calculations. I am not a fan of this type of heat pump. However, you save the cost of the thermal solar system (several thousand euros), probably only need a 150-liter (40-gallon) hot water storage tank (a few hundred euros less), and the installation is simpler. In addition, the cost of the gas connection (around 2,000 euros depending on the municipality) is eliminated, so the higher costs of the air-to-water heat pump can at least be partially offset.

Best regards
Thorsten

Bauexperte schrieb:
Well then, let's wait and see if your 2016 statement can actually be implemented

What do you mean by that, Bauexperte? Why would the general contractor include this solution in the construction contract if it then fails approval by the building authority? That would invalidate the entire construction contract—and that surely is not in the interest of the general contractor? Or am I overlooking some legal aspect?

Another way to approach the question of whether solar thermal systems are cost-effective:

If I need 80 liters (about 21 gallons) of water (two people showering daily) heated by 35° Celsius (from 5 to 40), I roughly require 3.5 kWh of energy. Assuming this energy (including additional energy needed to compensate for losses in the buffer tank) can be provided solely by the boiler over 8 months, it would save me 840 kWh annually. With gas at 80% efficiency of the gas boiler, I would need roughly 1100 kWh or about 170 liters (45 gallons) of gas, which costs around 55 Euros. With an air-to-water heat pump and a seasonal performance factor of 3.0, it would be about 370 kWh or roughly 80 Euros.

If, unrealistically, the solar thermal system could provide the required hot water every day of the year, the savings would be just over 80 Euros (gas) or nearly 120 Euros (electricity). Conclusion: Even if there are no capital costs, payback would be far beyond what is economically reasonable.

However, this calculation shifts significantly in favor of solar thermal if we assume that full baths are frequently taken in midsummer, because then the 4 m² (43 sq ft) of solar collector surface can deliver much more energy than the assumed 3.5 kWh plus buffer losses.
More realistically, the calculation shifts against solar thermal because the system cannot provide 100% of the required energy every day of the year.

This is just my way of looking at it.