ᐅ Building a Single-Family Home in North Rhine-Westphalia

You are discussing with unrealistic numbers that have nothing to do with reality. You can’t compare the forced air exchange rates of a controlled ventilation system with natural window ventilation.
When are ventilation losses particularly high? Correct, when there is a large temperature difference between inside and outside. What do I not do with window ventilation in that case? Right, I don’t leave the window open for a long time.

Does this reduce the relative humidity? Yes. Has anyone ever died from carbon dioxide poisoning because of it? No idea.

So, business majors... take a moment to think this through, and then good night.

toxicmolotow schrieb:
3.9 minus 1 equals 2.9... another step closer to break-even. And now add maintenance and filter costs... let’s leave that out. The calculation is tight (additional investment costs not included).

I don’t like repeating myself. Well, actually I do... So here is the calculation ONCE AGAIN:

Filter costs for 4 filters, each F7 and G4, when buying an empty frame and the filter separately: 25 EUR per year (quarterly filter replacement). I took the first available offer on Amazon for each, there might be cheaper options.

A mechanical ventilation system with heat recovery has an annual performance factor of about 15 to 20. For every 1 kWh of electricity consumed, you get back 15 to 20 kWh of heat.

Power consumption is approximately 35 watts per hour, which equals about 306 kWh per year. Energy savings therefore amount to approximately 4,599 to 6,132 kWh. This corresponds well with experience showing that with such ventilation you can size the heating at least 2 kW smaller (when using a heat pump).

At a gas price of 4.82 cents per kWh as we have, savings would be between 221.67 and 295.56 EUR per year.
Electricity costs for 306 kWh at 26.54 cents (quite expensive where we are) equals 81.21 EUR.

Electricity 80 EUR, filters 25 EUR, and financing 150 EUR add up to 255 EUR, or in other words, the system basically pays for itself at current prices and will save money if prices rise. Comfort, time savings, better indoor air quality, etc. all come as a free bonus.

And for us, the mechanical ventilation made solar water heating unnecessary. That saved about 5,000 EUR (we would have needed at least 3 solar collectors otherwise).

Not to forget, if you heat with an air-water heat pump, you pay significantly more than 4.8 cents per kWh of thermal energy.

We already discussed comfort. It doesn’t exist.

Better air quality, cleaner air, no longer having to manually ventilate constantly but still being able to ventilate at any time. No need to let freezing cold air in during winter while the child is playing. No need to air out once every hour during parties, and so on...
And a huge daily time saving, day after day.

Dust filters... whatever. But allergies are rising rather than falling. Want some disinfectant?

Allergies are indeed increasing. That’s why the F7 filter also captures pollen. This relief – at least during the 8 to 16 hours spent at home – significantly reduces the risk of allergy symptoms worsening for allergy sufferers.
According to current research, fine dust and diesel exhaust particles that attach themselves to pollen (which are otherwise harmless) and enter the body may contribute to allergies. The body recognizes the toxins (fine dust, diesel exhaust) but also forms antibodies against the pollen it mistakenly identifies along with them.
City dwellers have significantly more allergies than rural residents. It’s not due to the hygiene hypothesis or some magical dirt in the cow barn – this has long been tested. It is probably more related to the chronic exposure of city dwellers to the aforementioned pollutants (diesel, fine dust, etc.). Not to mention it’s proven that fine dust exposure causes arteriosclerosis and cancer. That doesn’t mean I want to completely isolate myself here. But if I can have better air for 8 to 16 hours a day, I’m happy about that. Especially since it’s FREE.

And a house without mechanical ventilation doesn’t necessarily develop mold either. So mold protection... whatever. I also have it without mechanical ventilation. So no definitive argument.

And a smoker doesn’t necessarily die from smoking. You are a RISK controller. Do I need to explain your profession? Of course, the RISK of mold is significantly higher in a house without mechanical ventilation than with it. Still, ventilated houses can get mold and non-ventilated ones might not. Similarly, lifelong non-smokers with no radon exposure can develop lung cancer in their 40s, while some smokers never do.

This is going too far. Self-consumption does not make photovoltaic panels owner rich. These just barely pay for themselves and don’t save a cent. Mechanical ventilation or not. I have a pool in my garden... I don’t save a cent because of photovoltaics. If the photovoltaic system lasts 10 years, I might slowly start to save.

And mechanical ventilation makes photovoltaics more profitable due to the base load. Just like that. Whether photovoltaics pay for themselves or not is irrelevant to this argument, dear Risk Controller. Those are sunk costs. But if the PV system is there anyway, mechanical ventilation makes it more profitable or at least less unprofitable. Depending on the case.

But these are all side issues. What matters is that mechanical ventilation pays for itself and in some cases is even profitable. Also important is that all the other benefits of mechanical ventilation come free of charge: better air quality in the city, less need to ventilate everywhere, lower pollen exposure for allergy sufferers, lower risk of mold, or higher resale value. All of that is included – free – with a mechanical ventilation system that pays for itself anyway. Or if you save 5,000 EUR by not installing an expensive and maintenance-intensive solar water heater – as in our case. Here it’s all literally free of charge.

The invoice is questionable simply because with a controlled residential ventilation system, I exchange significantly more air than I would through regular ventilation. I recover about 84% of what would otherwise be lost through conventional ventilation.

bierkuh83 schrieb:
Does this lower the relative humidity? Yes. Has anyone ever died from CO2 poisoning because of it? No idea.

Try searching for DIN 1946-6 or "DIN 1946-6 – Ventilation by Concept: Consequences and Conditions for Planning and Execution in Residential Construction."

Yeah, I know what you mean. We actually received a ventilation plan and an instruction manual for the house. Everything is great. When we are at home, there is sufficient ventilation. So far, no complaints about poor air quality. Controlled residential ventilation is more comfortable, blah blah blah...

Wow. Controlled mechanical ventilation – overwhelming discussion. I admit, I gave up trying to follow it all.

We have a controlled mechanical ventilation system, I have experienced it firsthand, and I think it’s fantastic! I really dislike having to open windows all the time (just imagine a child running around with a dirty diaper... you can almost see the smell. It’s wonderful when the bad odor is just sucked away immediately).
By the way, our building expert strongly recommends some kind of ventilation system when the house is sealed so tightly, as modern new builds often are. Whether it’s trickle ventilation, controlled mechanical ventilation, or automated window operation.
He has never seen residents ventilate properly on their own. Usually, they either ventilate too long, too briefly, or on the wrong sides. Apps and sensors might help a bit here.

On the topic: We also built with a budget provider (Heinz von Heiden) or rather, we are still building. Conclusion: We are completely satisfied. However, you have to be aware that you won’t get a full-service solution, and you have to manage many organizational matters yourself. Also, you must read the building specifications carefully so that unexpected work on your part doesn’t suddenly appear.
Whether we’ll still be happy with our choice in 20 years, I can’t say at this moment.
Our building expert is so far very pleased with the progress. Good materials, well-executed trades. And he doesn’t think highly of Heinz von Heiden overall. Every time he leaves the construction site, he grumbles because he finds nothing to complain about.

As with everything, a successful build depends on the assigned site supervisor and the craftsmen. If even one person involved is incompetent, it can quickly give you gray hairs.
Look around, read the building specifications thoroughly, and try to compare apples to apples to get comparable offers. Set your priorities (basement? Controlled mechanical ventilation? Large rooms? One-, two-, or three-story? Does the heating system matter? Is an included garage a must? Etc.)
And last but not least, trust your gut feeling. If you feel uneasy, the many interactions with your contact person will certainly not be enjoyable.