Poroton (36.5 cm) versus lightweight expanded clay aggregate solid wall (41 cm)

Hello dear community,

the topic has already been discussed in some posts here, but long-term experiences are missing.
Currently, I am planning a new 150 m2 house with a basement. We have now narrowed the choice down to 2 developers who differ fundamentally in the construction materials.
The house is planned to be built without insulation in a monolithic construction method. One developer wants to work with aerated concrete or Poroton (36.5 cm wall thickness), the other with a solid precast wall made of expanded clay with a wall thickness of 41 cm. We are now somewhat uncertain because the thermal transmittance coefficient is given by the developers as 0.21 (Poroton) and 2.2 (expanded clay). Both assure that the houses comply with the KFW 55 standard.
I am now unclear how the U-values can differ so much or whether other factors, such as the mortar used with Poroton, are taken into account. The insulation in the attic as well as the windows used (triple glazed) seem to be comparable in both cases. Are there any long-term experiences with expanded clay solid walls here in the forum?
Can you tell me whether a similar energy balance for heating can be expected based on the KFW 55 standard?
Our concerns are that with a heat pump and poor insulation, we will not achieve sufficient room heating or will cause extremely high heating costs due to additional heating with heating rods.

Best regards,
Sven

Both are absolute rubbish. Don’t just look at the thermal insulation but also at the soundproofing. These energy saving ordinance houses are unfortunately cardboard box shacks.

Take a 36.5 cm filled Poroton brick. Then you have something proper and you won’t regret it.

Both are absolute junk. Don't just look at the thermal insulation but also at soundproofing. These energy-saving regulation houses are unfortunately cardboard box shacks. Take a 36.5 cm filled Poroton brick. Then you have something real and you won't regret it.

What kind of flat and undifferentiated statement is that? What exactly is "cardboard" about a lightweight expanded clay aggregate (Liapor, Klimapor...) wall? HFP Liapor walls regularly meet the requirements of DIN 4219 – precisely because of the absorption effect of lightweight expanded clay surfaces. The same applies to lightweight expanded clay walls as prefabricated parts or, for example, made of Phonblock bricks – which also easily meet ÖNORM B 8115. Lightweight expanded clay per se provides good sound insulation.

Sorry, I probably confused it with Ytong in my haste!

Is there anyone in this forum who has built with [Blähton] and can share their experiences?

I am currently building with expanded clay (Klimapor, company Lechner Massivhaus, 49cm wall thickness) and - so far - I am very satisfied with the material and the system. The shell of the building was completed in 5 days - whereby here the shell means in the classical sense / it is by no means a closed building envelope like in timber frame construction. The execution is very precise - both factory-made and on-site. We are building in Bauhaus style and have two terraces on the upper floor, projections, cantilevered elements,... - therefore, of course, there are areas where additional insulation is applied to avoid thermal bridges. But over the large surface area, the house does completely without external thermal insulation composite system (ETICS). In my opinion, an absolute plus. In addition to the specific positive properties of expanded clay. We do not have a KfW certification - but that is due to our (active) air conditioning via multi-split devices. The heating load calculation of our building is effectively 4.8 kW for 200m2 of heated area.