We have decided on a prefabricated element construction method using 42.5 cm Liapor blocks without an external thermal insulation composite system (ETICS). But I think this should initially have no influence on your decision; it really depends on what you/you all value. For example, my wife did not want styrofoam on the outside of the house; at first, I didn't care.
I will now take the liberty of copying an overview of some types of solid construction from Bauexperte here:
Aerated concrete (Ytong is a 'manufacturer')
It is a highly thermal insulating solid building material that, due to its closed-cell pore structure, can take on both static and building physics properties – generally without additional measures or supplementary materials. It is made from domestic raw materials and has the almost unlimited lifespan characteristic of solid building materials.
Thermal insulation:
Aerated concrete is the only solid material with a thermal conductivity starting at 0.09 W/(mK) in the density classes 0.30, 0.35, and 0.40. This means: Even a single-layer 30 cm thick wall offers a thermal transmittance coefficient U = 0.28 W/(m²K). With a wall thickness of 36.5 cm, the U-value drops to 0.23. In the exterior wall area, the requirements of the Energy Saving Ordinance (EnEV) can thus be met and even exceeded without additional insulation measures. Moreover, the homogeneous wall structure allows for nearly thermal bridge-free constructions. A plastered single-layer wall made of aerated concrete is considered airtight according to the Energy Saving Ordinance without additional measures.
Heat storage:
The heat storage capacity of aerated concrete lies between the extremes of light construction (e.g., timber frame construction with about 50 kJ/m²K) and solid construction (e.g., masonry or reinforced concrete with about 250 kJ/m²K). The corresponding value for an aerated concrete wall is about 90 kJ/m²K.
Thermal conductivity:
Due to the very low thermal conductivity of 0.09 W/(mK), the requirements of the Energy Saving Ordinance can be met with aerated concrete in monolithic construction. A multi-layer structure in the case of an exterior wall, as common with other building materials, is omitted.
Diffusion resistance:
Due to the porous structure, the water vapor diffusion resistance factor of aerated concrete is low, lying between values of µ = 5 to µ = 10.
Building biology:
Aerated concrete is a natural raw material whose chemical and mineral structure is altered. This creates a product that is generally superior to natural raw materials and much better suited for the construction of buildings with high demands on lifestyle.
Sound insulation:
Aerated concrete relativizes the physical principle "The heavier a component, the better the airborne sound insulation." Because aerated concrete has, due to its pore structure, an internal damping effect. The DIN 4109 also takes this into account: aerated concrete walls with a surface mass up to 250 kg/m² receive a bonus of 2 dB. New component measurements even show further improvements. With walls and solid roofs made of aerated concrete, all exterior noise levels can be acoustically covered. After suitability test III for DIN 4109, two-shell party walls made of aerated concrete with 17.5 cm PP4-0.6 each and a 50 mm shell distance, completely filled with mineral insulation, even meet the requirements for increased sound insulation.
Fire protection:
With aerated concrete, you are on the safe side in case of fire. Aerated concrete is a mineral building material and non-combustible. Therefore, it is classified according to DIN 4102 as building material class A1 and, depending on the version, can be used for all fire resistance classes from 30 to F 180. Already a 7.5 cm thick unplastered non-load-bearing wall made of aerated concrete meets all requirements of fire resistance class F 90. Walls starting at 24 cm thickness made of aerated concrete PP 2-0.4 are considered firewalls. Ceilings and roofs made of aerated concrete also comply with the conditions of fire resistance classes from F 30 to F 180.
Expanded clay or lightweight concrete from Liapor
The production of lightweight concrete blocks from expanded clay is essentially carried out according to the technique of regular concrete stone production, where expanded clay is used instead of normal aggregate to reduce the bulk density and thermal conductivity. Expanded clay is artificially manufactured by forming ground clay into pellets and firing them at a temperature of 1100-1200°C. The natural or added organic components contained in the clay burn out, and the combustion gases expand the clay pellets so that fine pores form inside. At the surface, a relatively hard outer skin forms.
Thermal insulation:
The excellent "natural" insulation combined with a thermal insulation composite system easily meets legal requirements.
Heat storage:
Expanded clay warms up very slowly during the day and stores the heat. At night, the heat is released very slowly again. Expanded clay keeps the house cool during the day and comfortably warm at night.
Vapor diffusion:
Expanded clay is closed sintered and therefore cannot absorb moisture. The wall elements are breathable and ensure air humidity exchange. A crucial plus point for a health-promoting and comfortable indoor climate.
Building biology:
Expanded clay is natural. Produced resource-efficiently and without chemical additives, 1 cubic meter of raw clay yields up to 5 cubic meters of expanded clay pellets with excellent building biological properties.
Sound insulation:
Sound always seeks the path of least resistance. Sound must travel around each individual pellet in the expanded clay wall, thus covering a huge distance that significantly weakens its intensity.
Fire protection:
During the production of expanded clay pellets at 1100-1200°C, all organic components escape. Expanded clay exterior walls belong to the highest fire protection class F180.
Hollow bricks
The brick has been widely used as a natural building material for thousands of years. Due to its capillary structure, the brick is a natural moisture regulator. It is capable of absorbing, storing, and releasing room moisture quickly under favorable outdoor air conditions. Thermal insulation through bricks prevents the rooms from cooling down too quickly in the event of interrupted heating operation. During the hot season, due to its heat storage mass, the brick stores the accumulating heat inside the rooms.
Thermal insulation:
The heat absorbed by the massive brick walls and removed from the room is only released back to the room when it is cooler outside, thus allowing excess heat to be dissipated through natural ventilation. This ability of bricks to provide phase shift and amplitude damping of temperature has been long used in southern countries by constructing massive brick houses (without additional air conditioning).
Thermal protection:
Depending on density and λ-value, the brick has very good thermal insulation properties. Using lightweight bricks with densities of 0.8 kg/dm³ or 0.9 kg/dm³ and lightweight mortar LM 36, κ-values under 0.40 W/m²K can easily be achieved at a common wall thickness of 36.5 cm.
Thermal conductivity:
Walls made of hollow bricks without filling have higher thermal conductivity in the vertical direction, especially when laid with conventional thin-bed mortar that does not reliably seal the holes (convection!).
Diffusion resistance:
Monolithic brick masonry made from thermally insulating hollow bricks can achieve thermal conductivity values of up to 0.14 W/mK and with a thickness of 36.5 cm and plaster on both sides, a thermal transmittance coefficient (U-value) of about 0.35 W/m²K. This value requires the use of lightweight mortars LM 21 and unbanded but interlocked head joints. This results in a strict three-part composition in the cross-section of the building component of brick, air-filled head joint, and mortar bed joint. Each of these areas shows slightly different protective behavior against moisture.
Building biology:
The hollow brick meets the requirements of ecological building and building biology.
Sound insulation:
Already 30 cm or 36.5 cm thick single-layer exterior walls made of lightweight bricks laid with lightweight mortar and plastered on both sides generally meet the requirements of DIN 4109 "protection against external noise". The requirements for partition walls in DIN 4109 regarding sound insulation are easily met with walls made of bricks with densities up to 2.4 kg/dm³.
Fire protection:
The brick has already been through the fire on behalf of the builder during firing. Walls made of bricks, plastered on both sides, already meet the requirements of DIN 4102 for fire resistance class F90 "fire resistant" at 11.5 cm thickness.
Source: Bauexperte