ᐅ Is a mechanical ventilation system with heat recovery advisable in this case or not?

Hello Building Expert,

Bauexperte schrieb:
...If it stays within the minimum range (i.e., max. 3 panels), then yes; otherwise, rather not.

Why?

Bauexperte schrieb:
...I do not need to calculate myself; for that, I hire external specialists I work with, who, however—you have unfortunately often demonstrated—seem questionable to you.

Apparently not entirely without reason, as no solution to the original poster’s problem has been presented, only criticism of a manufacturer.

Bauexperte schrieb:
..., you still suspect advertising.

It would be relatively easy to disprove such “suspicions.”

Bauexperte schrieb:
...It repeatedly shows that you trust no one except yourself.

Completely correct, as long as opposing arguments are based solely on advertising.
Therefore, I advise every homeowner to be fundamentally critical before making rather significant investments based on questionable optimistic calculations.

Bauexperte schrieb:
...What you should really reconsider is your unpleasant way of increasingly discrediting me and reducing me to a mere brochure regurgitator. That is not only poor style; it is simply insulting.

You apparently find an opponent unpleasant especially when your own position begins to falter due to a lack of technical arguments.
I certainly provoke at times, but harming anyone’s honor is not intended and should not be understood as such.

Likewise, Merry Christmas

Well, Christmas, so just love it 🙂

I think, as always, there is more than one truth. And maybe the calculated difference is actually smaller in reality than originally assumed.

We also have a gas boiler plus a solar thermal system (6sqm (65 sq ft)) and didn’t negotiate because you can’t keep adding insulation to every wall of a house. The lower U-value would be zero.

In the end, it really depends on user behavior. Someone who only washes their hands with warm water probably won’t make full use of the solar thermal system. But my wife loves long warm baths and doesn’t just run the water once. I enjoy long showers. And my son is slowly starting to enjoy longer splashing sessions as well. We know all of that isn’t efficient and that there is potential to save more. The fact is, the system saves us real money. And since we had no additional costs in our case (they were likely already included in the base price somewhere) and we are receiving 2,500 from the KfW, that works out well.

The only negative aspect I see with a solar thermal system is that it is technical equipment that can break down, and it might reduce the space available for a photovoltaic system.

Of course, this is just the opinion of an amateur builder who nevertheless feels well advised. Accounting tricks aside, I’m sure we could have done many things better, but as a builder, at some point you get overwhelmed. Experts keep bombarding you with information and then you don’t know who is right. It’s like in my profession... Java or C++... purely a matter of belief that can certainly also be supported by facts.

Bauexperte schrieb:
... you still suspect advertising.

This seems to be some kind of witch hunt here in the forum.
Like in the Middle Ages.
Anyone who accuses others of advertising gets burned... I mean deleted, regardless of whether it’s true or not.
Except when it’s the Inquisition itself, of course—that’s above all else… Compliance at its best.

We also deliberately decided against solar panels. Our consumption is so low that payback is only possible very late.
Either energy prices have to rise significantly again, or the efficiency of solar systems has to improve considerably for it to be worthwhile.
But in the end, it’s a matter of perspective. Some people try to think ecologically and accept the additional costs.

Of course, if you ask a solar vendor whether to choose solar or not, you shouldn’t be surprised by the answer.

Hoping my post will not be deleted by the Inquisition, pardon, the administration, I remain

with Christmas greetings

Hello,

jorel schrieb:
This seems to be some kind of witch hunt here in the forum. Like in the Middle Ages.

Not only here, enlighteners are usually seen as witches and are persecuted by the inquisition, since they question the profit interests of some ;-)

I actually didn’t want to, but since Bauexperte demands very specific examples, I looked through my documents again:

Example 1:
Construction project near Dortmund, built in 2008, KfW 40 according to the definition at that time, high-end provider:
- Hot water demand according to proof => 2544 kWh/year, theoretical solar thermal system coverage rate 62%
The system should have delivered 1577 kWh/year.
Results of the subsequent performance measurements using a heat meter: 83.5 kWh (5.3%) !!!!

Example 2:
Construction project near Berlin, built in 2010, KfW 55
- Hot water demand according to proof => 2315 kWh/year, theoretical solar thermal system coverage rate 60%
The system should have delivered 1388 kWh/year.
Results of the subsequent performance measurements using a heat meter: 167 kWh/year (12%) !!!
This could go on endlessly.

One could also choose another title: Beware of fraudsters, con artists, and charlatans.

jorel schrieb:
...We consciously decided against solar as well. Our consumption is so low that payback is only possible very late.

A completely correct decision, because the actual energy demand for hot water has absolutely nothing to do with the definition according to the Energy Saving Ordinance/planning permission or KfW.
In addition, the actual utilization rate! (not efficiency) is significantly worse than generally assumed.

jorel schrieb:
...But in the end, it’s also a matter of opinion. Some try to think ecologically for themselves and accept the additional costs.

Correct, in principle, every kilowatt-hour of fossil energy saved is valuable.
However, the majority of homebuilders initially assume a solution that is overall economically viable for themselves.
Sometimes the ecological interest is only discovered afterwards when it is no longer possible to change the actually existing shortcomings. ;-)
Sellers know this very well, because after finishing a construction project, the homebuilder’s wallet is usually empty.
Often there is no possibility to assert one’s rights afterwards, regardless of whether it was even noticed that they had been taken advantage of.
Prevention is always cheaper than trying to fix things afterwards.

jorel schrieb:
...Of course, if you ask a solar salesperson whether to go solar or not, you shouldn’t be surprised by the answer.

Also correct, if you consult sellers who are inherently biased, objectivity regarding a solution that is economically viable overall for the homebuyer is likely to be a foreign word ;-)
On the other hand, that is perfectly legitimate, because those who do not educate themselves in time are more likely to fill other people’s pockets rather than protect their own. ;-) That certainly benefits the public as well, for example, in the form of financed VAT. ;-) Unfortunately, usually without equivalent direct benefit for the individual homebuilder.

Best regards

jorel schrieb:
...Even if the material survives the service life without hail damage or other defects (which, according to the manufacturers, rarely happens), the efficiency of the cells steadily decreases.

Do not confuse photovoltaic systems with solar thermal systems! These are two completely different things.
The main challenge with solar thermal systems is the storage of thermal energy. This issue does not arise with photovoltaic systems, as electricity is usually fed directly into the grid, using the "public grid" as storage.
Advertising, for example via links, is generally not welcome here, but this should not be a problem as long as the discussion remains focused on the topic itself.

Furthermore, this discussion has now deviated significantly from the original question of the thread starter, so it would actually be appropriate to end it here.

Best regards