Ventilation system in the new building, yes or no?

Basically, we could calculate that, but a lot of information is required.

I don’t know if it helps the person seeking an answer in a forum to just string together calculations, abbreviations, and formulas. Expertise is good, but a forum visitor wants their question answered. Therefore, in my opinion, it is also counterproductive if answers from other participants are dismantled. The questioner can judge for themselves and certainly does not need assistance there.

Nevertheless, my opinion:

That is unfortunately not physically possible. In practice, at best 60 ..70 % of the exhaust air energy is actually usable!

Wrong: current systems have an efficiency of 92%!

Every component exposed to solar radiation, even opaque ones, fundamentally uses parts of the solar energy! No ventilation is required for this!

Opaque? I don’t know that. Correct: Every component uses solar energy, but it’s about ventilation in living spaces. With window ventilation, solar energy would leave the house unused. In summer that’s no problem, but in the transitional period and in winter it is uneconomical. We should return to the question: It’s about a low-energy house!

Correct:
For buildings close to the passive house standard, a controlled living space ventilation/heat recovery system is indispensable.

The low-energy house is primarily mandatory due to the energy saving ordinance, and the KfW70 house is standard with most developers and also subsidized by the KFW with low-interest loans. So it is not necessarily a pure desire of the builder. Even though, of course, people like to live energy-efficiently and save energy costs. It should not be a dogma.

The controlled residential ventilation is intended to maintain a healthy indoor climate and prevent mold. If this is also possible with normal ventilation, great. Controlled residential ventilation without heat recovery does no more than air exchange. Filtering... okay. In the end, controlled residential ventilation remains a matter of comfort.

With controlled residential ventilation with heat recovery, it is different, and in terms of energy saving, it is certainly the ultimate. The question of economic viability can go either way; whether the efficiency is 70 or 90% is secondary. In any case, such a system initially involves an investment volume of around €10,000, which is simply not feasible financially, even if it saves €20,000 over 30 years of living.

Hello,

Basically, we could calculate that, but a lot of information is required.

Who is we and how would you calculate that? I do something like this almost daily!

... That is why, in my opinion, it is also counterproductive when answers from other participants are dismantled. The questioner can judge for themselves and certainly does not need any assistance there.

It is not about "dismantling" - but about objectivity!

...
Wrong: current systems have an efficiency of 92%!

Where do you get this statement from? Brochure or advertisement? Are the 92% part of the contract for your controlled residential ventilation? In all my measurements, I have never come across this. But I am willing to learn.
Currently, there is no industry that is as inventive with the definition of the efficiency of heat recovery as this one. We are now at the 12th version!

...
... uneconomical during the transition period and in winter.

What would be economical then? Investing 9,000 € to save x..600..y kWh annually?
By the way, at low outside temperatures, the drying potential is the greatest, as a look at the Mollier h-x diagram shows. This shortens the ventilation time and the associated heat loss due to ventilation!

In conclusion:
First clarify and have the necessity and the requirement examined. Then have the profitability calculated.
Anyone who has enough money can plan it without any verification for comfort reasons.

Regards

Hello,

Who is "we" and how would you calculate that? I do something like this almost daily!

It's not about "taking apart" - but about objectivity!

best regards

The calculation will be done by a specialist planner from the manufacturer company. But enough now. I understand you: you are right and everyone else is stupid. Please stop writing when you're having a bad day. And don’t act like a pro here.
--> I will not respond to any further posts from you on this topic!

Hello,

The low-energy house is initially mandatory due to the Energy Saving Ordinance and the KfW70 house is standard for most developers and additionally subsidized by the KfW with favorable loans. So not necessarily a pure wish of the builder.

The goal of the Energy Saving Ordinance and KfW funding is to save primary energy! This approach is basically positive, as it is about reducing environmental impact through CO2.
Future energy costs can primarily only be substituted by investment costs! To mitigate this additional investment effort, the MAP was established! This means that for the builder no economic efficiency is inevitably guaranteed!
The legislator has given both builders and planners full freedom of action with §25 Energy Saving Ordinance and §9 EEWG to come to an overall economical solution.
That these possibilities are mostly not used in owner-occupied residential buildings is probably due to a lack of skills.
Commercial clients behave quite differently, as economic efficiency is paramount here. It is checked whether the subsidy of the investment actually has an economic effect.

If that also works with normal ventilation, great.

Unfortunately, this is not always possible in general and as a rule! The necessity and requirement would have to be checked. Afterwards, the decision "pro" or "contra" would follow.

Best regards

That these possibilities are mostly not utilized in owner-occupied residential buildings is probably due to a lack of skills. Commercial clients behave quite differently here, as economic efficiency is the main focus. It is examined whether the subsidy of the investment actually has an economic effect.

Professionally, I quite often calculate the economic efficiency of investments. Expenses, income, savings, interest... This is not a mystery to me. I am an engineer, understand enough thermodynamics to know that heat recovery makes sense. All of that is useless, however, if the money for the measure is not available. Therefore, my concern is really only about what is absolutely necessary.

I have also read in another forum where quite a few people share their experiences. The general consensus regarding controlled residential ventilation: Super comfortable, but if it is not present, airing out also works, provided you are not too lazy to do it.

Unfortunately, this is not always generally and universally true! The necessity and requirement would need to be checked.

How? They mention a few factors that argue for and against it. As mentioned, we live as four people, shower and wash, dry laundry outdoors in summer, indoors in winter, a dryer would be conceivable. The climate is German, northern German, not a dry desert climate, not perpetually humid tropics, not permafrost, it rains here fairly often. The house has no basement, is well insulated, KfW70 standard... What other factors are there?

And the second question: If I remove moisture by normal regular airing, what else could make controlled residential ventilation absolutely necessary? Heat losses through warm air are the same when airing as with controlled residential ventilation without heat recovery, as long as you don’t let the walls cool down during airing.

To prevent a misunderstanding: I am not fixed on or biased against "without controlled residential ventilation," but I would like to understand why some say it is impossible without it. Because I have not yet read a convincing argument for it.