New construction: Limestone sandstone + thermal insulation composite system = mold?

Hello,

a construction financier advised us against buying a newly built semi-detached house because the exterior walls are made of sand-lime brick masonry and the facade is constructed as an external thermal insulation composite system with polystyrene rigid foam boards and synthetic resin plaster.

His reasoning: This is an airtight sealed house with zero breathing. Without a ventilation system in the house, mold would be inevitable. This construction method is only used to cheaply meet the Energy Saving Ordinance 2009 and is no longer up to date.

Unfortunately, I have no knowledge about construction or modern energy-efficient building.

Is what he says true?

I ask for your opinion.

Thank you in advance.

Hello K1300S,

thank you very much for your reply.

What alternatives are there for the masonry to comply with the Energy Saving Ordinance 2009, so that you do not need a "controlled residential ventilation"?

Best regards

What alternatives are there in masonry to comply with the Energy Saving Ordinance 2009 so that you don't need "controlled residential ventilation"?

There will be various possibilities in masonry (e.g. monolithic construction, clinker), but the problem of the airtight house remains!!!

As already mentioned: You do not have to have a controlled residential ventilation system, but apart from that, the Energy Saving Ordinance provides very clear guidelines regarding the airtightness of the building envelope, and thus all houses that comply with this (and these are all that are built nowadays) are equally affected - regardless of whether with KS, PB, hollow bricks, HRB, ...

Otherwise, you will probably have to build in the USA or elsewhere.

Best regards

K1300S

Hello,

....ein Baufinanzierer hat uns von dem Kauf....Stimmt das was er da erzählt?..

What professional training/ qualification does this "advisor" have, especially in the field of building physics?

Best regards

Hello,

His reasoning: This is an airtight sealed house with zero breathing. Without a ventilation system in the house, mold would be inevitable here. This would only be done to achieve the 2009 energy saving ordinance in a cost-effective way and is no longer up to date.

Well, then the building financier probably wouldn't have much to do, because mostly thermal insulation composite systems (ETICS) are still being installed.

The user "K1300S" described it very aptly; walls don't really breathe, but where an ETICS is installed, no diffusion takes place at all. Here ventilation is - from my subjective point of view - mandatory; whether central or decentralized, because on the one hand the builders don't have an eye for a correct calculation (sometimes it actually works without ventilation), and on the other hand they have no time to comply with the required ventilation intervals during the first years after moving in.

By the way, the further explanation of the building financier is not correct. Many contractors (BU), especially older ones, use sand-lime bricks (KS), because then they have nothing at all to do with sound insulation; the builders later cannot at least complain about this point. But since KS has catastrophic thermal insulation, a thicker ETICS has to be applied. KS is therefore suitable in regions such as near railways or airports in combination with soundproof windows.

The same applies to perforated bricks or aerated concrete or pumice, among others, which are installed with a wall thickness of 17.5 cm. Here too, an ETICS must be applied for necessary thermal insulation.

From my perspective over the last years, ETICS are installed fundamentally - apart from the aforementioned restrictions - because then the settlement cracks of the house disappear behind the facade. Builders are more willing to accept them inside the house than to discuss exterior issues with neighbors. Few salespeople are, conversely, well enough trained to educate potential builders about the advantages of monolithic construction.

Rhenish greetings