ᐅ 36 cm Ytong exterior wall, solid construction, mold formation, insulation

o.s. schrieb:
...ETICS made of polystyrene crumbles at least just as much.

That may be true, but in this context it plays a rather minor role (load transfer or input). Besides, there are alternatives available.

o.s. schrieb:
...Do you see differences in stability between aerated concrete, perforated bricks, and bricks filled with perlite or mineral wool?

The required stability of the load-bearing envelope is determined by structural engineering calculations, which applies to all of the mentioned options.

o.s. schrieb:
...In our case that would mean at least 22,000 euros more – not including decorative hand-formed facing bricks. We neither want nor can afford that, even without golden door handles...

Compared to what exactly? Moreover, it generally makes sense to invest in fundamental and sustainable solutions, possibly by sacrificing a few cubic meters (meters) of built space.

This seems like a general contractor/main contractor tactic to steer the client into their own concept.

o.s. schrieb:
...Nothing to understand here.

Increasingly, buildings run into problems during summer heat periods due to rising energy saving regulations or funding requirements (such as KfW). The reason is quite simple: summer thermal protection is often treated very poorly. The consequence is that, especially with lightweight construction, air conditioning systems frequently need to be retrofitted—or occupants just have to endure the heat! The energy and investment efforts required for this were, of course, not previously considered. One could be suspicious of this.

Calculations of cooling loads or indoor temperatures during summer heat periods are mostly not carried out. Again, one might suspect something.

The list of pointless waste of money could go on indefinitely.

For example, if you rely on a heat pump as the heat source, excessive insulation may be unnecessary depending on the source, since that insulation does not help with domestic hot water demand. A photovoltaic system, for example, can help achieve a near "zero cost" annual energy balance for heating plus hot water. A pleasant side effect is that when photovoltaic modules are mounted above the roof surface, they also reduce cooling loads.

There are plenty of passive options in the building design to avoid potentially necessary active cooling (mechanical refrigeration) in summer.

Best regards.

Hello €uro,
regarding the load-bearing wall, I just wanted to ask what you meant by "The various 'crumb stones' are sometimes a joke.", especially since we plan to build using crumb stones as well. My specific question: Given the thermal conductivity (λ), in my opinion, aerated concrete is cheaper than hollow bricks, and those are much cheaper than "modern" bricks with insulation filling. I tend to prefer the most expensive option, although neither structurally nor financially can it be justified. I was hoping you could provide more arguments regarding "crumb stones" here...

Your comment about summer thermal protection and airtightness according to the energy-saving regulations is helpful, but in my opinion, the preferred method is a controlled mechanical ventilation system with heat recovery. Depending on the ventilation habits and insulation standard, this can
a) save 50% or even more of primary energy consumption,
b) provide some cooling in summer, and
c) eliminate mold problems.

What is your view? Wouldn’t this be more efficient than investing money in photovoltaic systems and, at the same time, unfairly taxing non-photovoltaic owners through taxes, or installing questionable air-to-water heat pumps that could only be environmentally friendly if the electricity itself were already produced sustainably?

o.s. schrieb:
....Regarding the load-bearing wall, I only wanted to ask what you meant by "The various 'crumb stones' are sometimes a joke.", especially since we plan to build with crumb stones as well.

Well, in my opinion, crumb stones are especially aerated concrete with a thermal conductivity (λ) less than 0.1. Just take a drill with a 10mm (0.4 inches) bit and drill a hole, then measure the diameter afterwards. For heavy loads (anchor points), expensive special anchors are required. If my fingernail leaves a lasting mark on the "stone," to me it is no longer a stone.
It also does not provide high internal building mass (thermal storage capacity), which can noticeably affect the performance of the installed systems.

o.s. schrieb:
....My specific question: With a given λ, I think aerated concrete is cheaper than hollow bricks and those much cheaper than "modern" bricks with insulation filling.

Price comparisons are not simple. The free market is quite regionally diverse. Additionally, contracts with general contractors (GCs) or construction managers follow different rules.

o.s. schrieb:
....Your reference to summer thermal insulation and airtightness according to the energy saving regulations is helpful, but in my opinion, the preferred method is controlled mechanical ventilation with heat recovery. Depending on the ventilation behavior and insulation standard, it is possible to
a) save 50% or even more of primary energy consumption, ...

Primary energy is certainly useful data, but mostly only relevant for certification purposes. What really matters is end energy—how much end energy is saved? Overall, this is quite a bold claim. Please provide a concrete and verifiable example.
The actual cooling effect of controlled mechanical ventilation is often greatly overestimated. Quite a few systems have to be shut off occasionally in summer despite having a bypass. Furthermore, it would be necessary to know beforehand what cooling capacity is required and what can be provided by the controlled ventilation system. Any examples?

o.s. schrieb:
....What is your view? Wouldn’t that be more efficient than investing money in photovoltaics and drawing unsolidarily from the taxes of those without photovoltaics, or installing questionable air-to-water heat pumps that would only be ecological if the electricity was already produced from green sources?

The boundary between personal budgets, solidarity, and environmental conscience is something everyone has to find for themselves. It is not uncommon for builders to discover their green conscience only afterwards when it becomes clear that their concept failed economically. By the way, an air-source heat pump is not questionable at all but can be a very good choice—if the conditions are suitable. Such broad statements are unrealistic and show little technical understanding.
A well-designed air-source heat pump system achieves a seasonal performance factor (SPF) around 3.5 or slightly better. Assuming an annual demand of 10,000 kWh (for heating and domestic hot water), about 2,857 kWh would be drawn from the grid, with the rest supplied by the environment.
With a gas condensing boiler, about 12,500 kWh must be purchased from the supplier—9,643 kWh more.

Best regards,

NB: Forum discussions do not replace the necessary planning, sizing, and consulting. They can only at best inspire thought, nothing more!

Hello €uro, thanks for the information about the bricks with λ < 0.1! I will get some bricks myself...

Overall a rather bold claim Please provide a concrete and verifiable example for this.

Example:
Region: Berlin, heating season mid-October to end of April,
170 sqm (1827 sq ft) area, 2.50 m (8.2 ft) ceiling height.
Air exchange rate 0.5/h (recommended minimum): heat loss: 5889 kWh per heating season.
With 80% efficiency, (theoretically) 4711 kWh could be saved - minus the kWh for the fan motor...

How do I arrive at this?
A small tip: just google "heat demand" and "U-value" and you will find help.

By the way, an air source heat pump is by no means questionable, but can often be the first choice, depending on the conditions Such general statements are unrealistic and show little technical understanding.

Thanks for the compliment. Professional expertise is indeed absent, only knowledge read about building physics and technology.

A well-planned air source heat pump system achieves a seasonal performance factor (SPF) of about 3.5, possibly a bit better.

Exceptions prove the rule (seasonal performance factor ≤3)? When I google field tests, I always find results significantly worse than the manufacturers’ data... Where is the truth?

Assuming an annual demand of 10,000 kWh for heating and domestic hot water, 2857 kWh would be drawn from the grid, the rest supplied by the environment. With a gas condensing boiler, I have to obtain about 12,500 kWh from the supplier. So 9,643 kWh more.

At what efficiency do fossil fuel power plants generate their electricity? 40-45%? How much loss occurs in the distribution lines? (6% or more)

Ah, always the question about the right building material. There are those who swear by aerated concrete (many greetings to Bauexperte), then there are others who prefer bricks. And there are actually people who still favor calcium silicate blocks. Every type of masonry has its pros and cons…

If good insulation is the goal, aerated concrete is certainly a good option, but this comes with, and here building physics cannot be ignored, a compromise on sound insulation. Mass remains the fundamental requirement for effective soundproofing. When it comes to summer thermal protection, aerated concrete also has limitations, as mass is essential here as well. Additionally, aerated concrete is not ideal for point load-bearing from a structural perspective.

I am also not a fan of ETICS (External Thermal Insulation Composite Systems). These should be used only for renovation after careful planning. To me, a massive and solid construction method is a cavity wall with a facing brick outer layer. Aside from somewhat higher costs, I don’t know of any disadvantages to this building method.

Which building material someone chooses depends on what is most important to them—sound insulation, thermal insulation, summer heat protection, load-bearing capacity (for complex structures). General statements like aerated concrete, bricks, or calcium silicate blocks being the best material just don’t work. It always depends on the needs and requirements.

I must admit, however, that I see the most advantages in calcium silicate blocks. And in the end, of course, all components as well as the building services must be coordinated.

Regards

o.s. schrieb:
...Air exchange rate 0.5/h (recommended minimum): Heat loss: 5889 kWh per heating season. With 80% efficiency, (theoretically) 4711 kWh could be saved – minus the kWh used by the fan motor...

Then believe in that nonsense By the way, the waste heat from the fan motor is actually utilized!

o.s. schrieb:
...A small tip: Just google "heat demand" and "U-value" and you will get help.

I know those sites. They do more harm than good.
Then ask them for a written warranty for this nonsense. However, I doubt you will get anything Suspicious minds might think ill here.

o.s. schrieb:
...professional expertise is indeed not present, only recited knowledge about building physics and technology.

That has not gone unnoticed.

o.s. schrieb:
...Exceptions prove the rule (annual performance factor <=3)? When I google field tests, I always find significantly worse values than the manufacturers’ specifications... Where is the truth?

Manufacturer data has nothing to do with real-life systems. These field tests often include every major mistake of flawed or missing planning and sizing. Manufacturers are frequently—but wrongly—held responsible. They had absolutely no planning assignment! If some builder or general contractor cobbles something together, you cannot blame the equipment manufacturer.
Anyone who thinks that modern system technology can be used without solid and precise initial assessments, planning, and dimensioning for maximum energy efficiency is mistaken. They might as well choose an open wood fire as a heat source!

o.s. schrieb:
...With what efficiency do fossil power plants generate their energy? 40-45%? How much loss occurs in the distribution lines? (6% or more)

Who actually cares? The vast majority of my clients primarily look out for their own interests, and I can’t even blame them—I actually understand that.