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

Hello, we have now received a quote from a general contractor for our planned single-family house, which we actually liked.

However, a prefab house builder told us that if the house is built with solid construction, insulation should definitely be installed as well, otherwise mold problems will occur.

What do you think? KfW energy efficiency standards are not relevant in this case.

E.Curb schrieb:
.... The question is: Is a 36cm (14 inch) aerated concrete block really solid?

I can only agree with that. Various "crumbly blocks" are sometimes a joke.
Given today’s requirements, dividing responsibilities makes sense, meaning assigning the sometimes competing demands to different "specialists." Ideally, this results in a cavity wall construction plus a solid outer cladding.
Many do not want or cannot afford this, as they usually prefer features like gold-plated door handles, marble in the bathroom, or a dormer window instead.
It is no coincidence that the need for mechanical cooling is increasing with so-called "lightweight construction." When you calculate the actual energy balance here, what is called Passive House or KfW55 quickly becomes just a simple energy saving regulation standard.

v.g.

Hello €uro

€uro schrieb:
(...) The various "crumbly stones" are sometimes a joke.

Can you explain that in more detail? ETICS (External Thermal Insulation Composite Systems) with expanded polystyrene crumble at least just as much. Do you see differences in stability between aerated concrete, hollow clay bricks, and bricks filled with perlite or mineral wool?

Given today’s requirements, "separation of powers" makes sense, meaning that the partly competing demands are assigned to respective "specialists." Ideally, this results in a cavity wall construction plus a solid facing. Many don’t want or can’t afford this, as golden door handles, marble in the bathroom, or a dormer are usually prioritized instead.

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

It’s no coincidence that the need for mechanical cooling in so-called "lightweight construction" is increasing. When you calculate the real energy balance, a passive house or KfW55 standard quickly turns into a simple energy-saving regulation standard.

I don’t understand at all.

Regards
Olaf

Hello,

E.Curb schrieb:

.... The question, however, is: Is a 36cm (14 inch) aerated concrete wall really solid?

Here he is again; I really appreciate your subtle humor

E.Curb schrieb:

And keep in mind that the masonry must also meet other requirements --> structural stability / sound insulation. So when choosing the right building material, always look beyond the obvious.

[A]erated concrete[/A]

This is a high thermal insulation solid building material that, thanks to its closed-cell porous structure, can fulfill both structural and building physics requirements – usually without additional measures or supplementary materials.

ound insulation:

Aerated concrete challenges the physical principle "the heavier a component, the better the airborne sound insulation." Its porous structure provides a kind of internal damping. The DIN 4109 standard also takes this into account: aerated concrete walls with a surface mass up to 250 kg/m2 receive a bonus of 2 dB. Recent component measurements show even further improvements. Walls and solid roofs made of aerated concrete can cover all outdoor noise level ranges in terms of sound protection.

According to suitability assessment III for DIN 4109, double-leaf party walls made of aerated concrete with two 17.5cm (7 inch) PP4-0.6 blocks and a 50mm (2 inch) cavity, fully filled with mineral insulation, even meet the requirements for enhanced sound insulation.

Source: my homepage

Kind regards

Hello,

olali2 schrieb:

We were told (by a prefab house builder) that if the house is built with solid construction, thermal insulation must definitely be installed, otherwise mold problems will occur.
What do you think? KfW values can be neglected here.

I really appreciate these "expert" statements. By now, it should be well known that I am not a fan of hazardous materials; therefore, my answer will probably not surprise anyone.

As my insightful friend already pointed out, there is nothing against a monolithic wall structure. However, it must also be considered that, according to energy-saving regulations, houses have to be built quite airtight (in my opinion, too airtight). So you need to ask yourself whether you have the time to ventilate your rooms properly, especially during the first year after moving in. Even if the aerated concrete is bonded, a lot of moisture still enters the house through the screed—and consequently through human respiration. You should at least consider installing a ventilation system.

With monolithic construction—and if a partner is home most of the time—you can (just barely) do without ventilation. If you add external thermal insulation composite system (ETICS, also known as external wall insulation), however, I would reduce the wall thickness; unless you are aiming for KfW 55 standards—in that case, you no longer have this option because mold is then guaranteed. That sums up the statement from your prefab house builder.

Kind regards

Hello,

o.s. schrieb:
... However, a second protective layer is missing, so the structural builders have to work carefully to avoid thermal bridges ...

On one hand, and on the other, external wall insulation systems (EWIS) are commonly used today because the hairline cracks caused by normal settling are then "hidden" behind the rigid foam insulation.

Kind regards