ᐅ We are planning to build a house. Is what has been offered to us acceptable?

So, I’m using 17.5cm (7 inches) blocks for non-load-bearing interior walls... I just have a weird feeling about such thin exterior walls. The insulation might be okay, but if I’m building solid, then I want it to be truly solid.

But that’s just my amateur personal opinion.

Alex

Hm, but okay. For me, it is already a valuable statement that the structural design is the main driver here, and not primarily the insulation or other factors.

It always depends on the wall. An aerated concrete block also provides insulation (at the expense of thermal mass and soundproofing) and must also bear the load. For cavity walls, it is common to separate the structural support and insulation (although this is not mandatory).

Simply put: the heavier the material, the worse the insulation but the better the soundproofing and thermal mass; the lighter the material, the better the insulation but the poorer the soundproofing and thermal mass.

For example, aerated concrete weighs about 400 kg/m³ (25 lb/ft³), a perforated clay brick around 700 kg/m³ (44 lb/ft³), and calcium silicate brick up to 2200 kg/m³ (137 lb/ft³) – these values are approximate, especially for bricks, since there are around 100 different types with varying porosity.

This is largely a matter of opinion. Some people swear they can hear their neighbors on the terrace through an aerated concrete wall, others reject aerated concrete because of the aluminum content, some praise natural clay bricks and criticize mineral wool, while others insist that only a solid (monolithic) wall makes a proper house… and so on. But everyone agrees on one thing: PU foam smells bad.

BeHaElJa schrieb:

It always depends on the wall. A cellular concrete block also provides insulation...

**Cellular concrete

This is a high thermal insulation solid building material that, due to its closed-cell pore structure, can fulfill both structural and building physics functions—generally without additional measures or supplementary materials. It is made from locally sourced raw materials and has the almost unlimited lifespan typical of solid building materials.

Thermal insulation:

Cellular concrete is the only solid building material with a thermal conductivity starting at 0.09 W/(mK) in density classes 0.30, 0.35, and 0.40. This means: a single-layer 30 cm (12 inches) thick wall already offers a thermal transmittance coefficient (U-value) of 0.28 W/(m²K). With a wall thickness of 36.5 cm (14 inches), the U-value drops to 0.23. In external wall applications, this allows compliance with—and even exceeding—the requirements of energy saving regulations (building permit / planning permission) without extra insulation measures. Furthermore, the homogeneous wall structure permits nearly thermal bridge-free construction. A plastered single-layer cellular concrete wall is considered airtight for the purposes of energy saving regulations without additional measures.

Heat storage:

The heat storage capacity of cellular concrete falls between the extremes of lightweight construction (e.g., timber frame construction with about 50 kJ/m²K) and heavyweight construction (e.g., masonry or reinforced concrete with about 250 kJ/m²K). The corresponding value for a cellular concrete wall is approximately 90 kJ/m²K.

Thermal conductivity:

Thanks to the very low thermal conductivity of 0.09 W/(mK), energy saving requirements can be met using cellular concrete in monolithic construction. A multilayer wall assembly, which is common with other materials, is not necessary for exterior walls.

Diffusion resistance:

Due to its porous structure, the water vapor diffusion resistance factor (μ) of cellular concrete is low, ranging between μ = 5 and μ = 10.

Sound insulation:

Cellular concrete challenges the physical principle “the heavier a component, the better its airborne sound insulation” because its pore structure provides an intrinsic damping effect. The German standard DIN 4109 reflects this: cellular concrete walls with a surface mass up to 250 kg/m² (51 lb/ft²) receive a 2 dB bonus in sound insulation. Recent component tests indicate even further improvements. Walls and solid roofs made from cellular concrete can acoustically cover all external noise level ranges.

Hollow clay brick

Clay bricks have been used as a natural building material for thousands of years. Due to their capillary structure, bricks act as a natural humidity regulator. They can absorb, store, and release indoor moisture quickly under favorable outdoor conditions. Thermal insulation by bricks prevents rapid cooling of rooms during interrupted heating operation. During hot seasons, bricks store accumulated indoor heat thanks to their thermal mass.

Thermal insulation:

The heat absorbed and removed from the room by massive brick walls is only released back into the room when the outside temperature drops, allowing excess heat to be vented naturally. This ability for phase shift and amplitude damping of temperature has long been exploited in southern countries through massive brick buildings (without additional air conditioning).

Heat protection:

Depending on density and lR-value, bricks offer very good thermal insulation. For example, lightweight bricks with densities of 0.8 kg/dm³ (50 lb/ft³) or 0.9 kg/dm³ (56 lb/ft³) and lightweight mortar LM 36 can easily achieve U-values below 0.40 W/m²K with a typical wall thickness of 36.5 cm (14 inches).

Thermal conductivity:

Walls made from hollow clay bricks without cavity filling have higher thermal conductivity vertically, especially when built with traditional thin-bed mortar that does not reliably seal the cavities (causing convection!).

Diffusion resistance:

Monolithic masonry walls made from thermal insulating hollow bricks can reach thermal conductivity values up to approximately 0.14 W/mK and with a thickness of 36.5 cm (14 inches) and plaster on both sides, a U-value of about 0.35 W/m²K. This requires the use of lightweight mortars LM 21 and unmortared but interlocking vertical joints. Strictly speaking, the wall cross-section is split into three parts: bricks, air-filled vertical joints, and mortar bed joints. Each part has slightly different moisture protection behavior. The theoretical water vapor diffusion resistance factor for air-filled vertical joints is μ = 1, while for mortar bed joints it ranges from μ = 15 to 35 for lightweight and normal mortar. Various studies show that the influence of bed joints and especially the unmortared vertical joints on the overall water vapor transport through the component is negligible [2]. This also applies to vertical joints up to 1 cm (0.4 inches) wide. Compared to wax-sealed joints, the experiment found an average diffusion resistance factor of μ = 8.8 versus 7.3 for a 1 cm (0.4 inches) air-filled gap. Therefore, monolithic, highly insulating masonry can be assumed to have uniform and uncritical diffusion behavior. Also, in these single-layer plastered constructions, due to linear temperature behavior and corresponding linear partial vapor pressure gradients within the structure, condensation will never occur.

Sound insulation:

Single-layer external walls built with lightweight bricks and lightweight mortar, 30 cm (12 inches) or 36.5 cm (14 inches) thick, plastered on both sides, usually fulfill the requirements of DIN 4109 “Protection against external noise.”

The sound insulation requirements for partition walls according to DIN 4109 are easily met with bricks having densities up to 2.4 kg/dm³ (150 lb/ft³). Following suitability test III for DIN 4109, double-layer party walls made from cellular concrete with two 17.5 cm (7 inches) PP4-0.6 blocks and 50 m

Calcium silicate brick

Calcium silicate brick consists of a mixture of lime, sand, and water, pressed and hardened without chemical additives. The curing temperature in this environmentally friendly production is 160 - 200°C (320 - 390°F). This relatively low steam-curing temperature results in low energy consumption during production, producing no harmful substances. Therefore, calcium silicate bricks contribute significantly to energy savings and ecological balance.

Thermal insulation:

Thermal insulation properties are poor. Thermal conductivity ranges from 0.5 to 1.3 W/mK depending on density.

Heat storage:

Due to the high thermal conductivity in external walls, additional thermal insulation is indispensable to meet energy saving regulations. Highly insulated external wall constructions meet the demands of ecological building.

Sound insulation:

Calcium silicate bricks have a very high density and are therefore very heavy. This gives them excellent sound insulation properties. Because they are also very strong under compression, thin, highly load-bearing walls with very good sound insulation can be constructed using calcium silicate bricks. With cavity spacing fully filled with mineral insulation, even increased sound insulation requirements can be met.

BeHaElJa schrieb:

.... there are people who reject possible cellular concrete because of the aluminum

What does that mean exactly?

**Source: my HP

Regards, Bauexperte

If you are very environmentally conscious, you will meet people who are "afraid" of aluminum—whether in water bottles or deodorants—because it is suspected to contribute to Alzheimer’s disease (not proven or confirmed). For this reason, they also reject aerated concrete blocks, which get their pores through the heat treatment of aluminum.

There are also people who dislike reinforced concrete because it affects the radiation field, and so on...

Thanks, building expert! The digression was worthwhile. I didn’t know much about calcium silicate bricks before.

@LittleWulf: Is this your first offer, or have you already obtained several quotes on the “market”?