Insulate new construction 36.5 aerated concrete?

The Stone Age was in quotation marks... It is simply the currently lowest possible standard. After the next amendment of the Energy Saving Ordinance, it will be outdated.

Of course, sound insulation does not play a role everywhere, so it is individually what makes sense. I already said, I just can’t stand this black-and-white thinking. Aerated concrete is simply cheap, you can build monolithically if you want, it certainly has its justification.

And the U-value comments... windows weigh much more than the wall surface... Oh man. Troll.

I see it differently: twice as much heat passes through a state-of-the-art triple-glazed window as through the same area of wall according to the standard from 50 years ago: 30 cm (non-porous) single-layer brick.

As far as the attitude towards construction methods with or without insulation boards is concerned, it should not be completely overlooked: in new construction, achieving a certain standard is promoted regardless of the method; however, the insulation board "considered on its own" receives financial support especially for retrofitting.

In this respect, the new-build contractor already has a different perspective on this than the renovator.

Triple glazing with a good U-value is simply standard nowadays. There is not much room for improvement on that front anymore. The wall surfaces are the significantly larger potential lever, especially if you only have 36 cm aerated concrete walls.

I already have a preliminary calculation and it says 42.7% heat loss through ventilation, 26.9% through glass, and 10.8% through the exterior wall. And that is then related to the heating energy.

If we assume 8,000 kWh heating and 4,000 kWh hot water (about 180-190 liters of hot water demand per day for the entire family including losses, etc.) that’s 12,000 kWh.

Of that, 10.8% (of the 8,000 kWh heating energy) equals 864 kWh through the exterior wall. Out of a total of 12,000 kWh!

If you save 25% (!) => 216 kWh per year => 10.41 EUR savings per year here with the current gas tariff => 87 cents discount per month.

Sound insulation well, can’t be calculated exactly.

Aerated concrete 350 kg/m3 x 0.365 => 127.75 kg/m2
Sand-lime brick 1800 kg/m3 x 0.175 => 315 kg/m2

Mass initially more with sand-lime brick, clear.

Now aerated concrete gets a surcharge because of the pore structure and sand-lime brick with EPS gets a reduction of sound attenuation, since EPS amplifies sound (!), unlike mineral wool.

Regarding lifecycle costs: Based on the extremely minimal advantage of EPS insulation (above e.g. 10.41 EUR per year, i.e. 520.50 EUR over 50 years) it becomes clear that of course it does not have to be the case that the ETICS falls off the wall after 3 years. It will not do that. But even the smallest renovation damage cancels out the advantage compared to monolithic. A single woodpecker, a single mechanical impact, a single algae infestation after 30 years, etc.

Basically, it will be like this though, you have to renew the ETICS facade at least once. A monolithic wall does not. Here with us many ETICS facades are already going into renovation. Of course, you can say that ALL of them were improperly executed and partly that may be true and it is also noticeable that houses without eaves are frequently affected. But for the 10 EUR per year I don’t want to make any bets.

I assumed in 2013 that anyone who has to wrap a new house in Styrofoam has done something wrong. And I used 36.5 porous concrete and am satisfied. Chasing the last percent of heating cost savings with very low costs and spending a lot of money on it is economically nonsensical. It may be that a flawlessly installed WDVS lasts for decades. But who knows if the craftsman works flawlessly and the planner plans flawlessly? If a system is so susceptible that even minor errors trigger expensive repairs barely ten years later, I distance myself from the system. With the money saved, one can almost indefinitely finance any additional consumption if interest rates rise back to normal levels. Without having to fear that defects will occur.

What would be sufficient coverage with plaster to prevent algae growth? Which type of plaster should be preferred?

My knowledge:

- thick (>1.5cm)
- mineral-based
- vapor permeable, so also not painted with water-repellent paint, etc.

So exactly the opposite of what is usually done (cheap thin-layer plaster made of synthetic resin, painted with water-repellent paint, presumably including pesticides against the algae)

If you save 25% (!) => 216 kWh per year => 10.41 EUR savings per year here with the current gas tariff => 87 cents deduction per month.

Well, where do the 25% come from, what kind of target is that?
The point is that monolithic construction is more expensive to achieve the same insulation standard as with ETICS - especially EPS. This is clearly stated in the offers available to us. And we all have to meet an insulation standard, if only according to the Energy Saving Ordinance. Reaching KfW 55 standard is then relatively peanuts, because only a few more cm of EPS would be needed. Opposed to that are €5,000 repayment subsidies and interest advantages through KfW loans.
Therefore, I find the approach strange to assume a fictitious 25% as "savings" and estimate some consumption. Then calculate against that every gap in the monolithic wall represents a thermal bridge. Also the ceiling against the outside air.
Don’t get me wrong, I would also like to build monolithically. It feels like the "right" thing. But the extra cost is simply there, I also like sand-lime brick and two-shell brick with clinker is not possible here (in my opinion the absolute ideal).

A single woodpecker, a single mechanical impact, a single algae infestation after 30 years, etc.

Whoever has the ominous woodpecker damage chose the cheapest of the cheap variants. Take a laminated EPS board, mineral wool and/or thick-layer plaster, then that belongs to the realm of myths.
Algae infestation is reducible but incidentally also occurs on monolithic walls, although more rarely. Some environmental influences simply cannot be dismissed, e.g., proximity to forests.

Currently, many people build houses with white plaster facades. No matter how you look at it, they will tend to require cleaning sooner or later, whether there is ETICS underneath or a monolithic wall structure. Sure, if algae growth occurs, then earlier and/or more often, but they all get dirty.