New single-family house (KFW70)/aerated concrete vs. sand-lime brick/what to use?

Hello €uro,

which competing claims do you mean? With a 36.5 AW and above?

That a monolithic exterior wall is cheaper compared to an AW with WDVS would be new to me. Even compared to a double-shell plaster construction, the savings are limited.

Rhenish greetings

Hello construction expert,

...which competing demands do you mean? ...

The topic has already been vacant several times in this forum!

1. - Structural engineering (load transfer)
2. - Thermal insulation
3. - Summer heat protection
4. - Sound insulation
5. - Facade or weather protection

Even a layperson should become aware that these different requirements can hardly be exhaustively and optimally met in detail by monolithic wall construction alone.
This necessarily leads to a multi-layered AW construction, in which each layer takes exactly the part that it can fulfill particularly well.

An optimal AW construction could look like this, for example:

1. Inner shell: e.g. high-strength, heavy sand-lime brick or brick (17.5 cm):
Advantage: very good internal heat storage capacity, excellent load transfer (no special dowels for point loads), very good sound insulation
Disadvantage: poor thermal insulation

2. Thermal insulation (WLS and thickness as needed/required)
Advantage: very good thermal insulation (main component of a construction)
Disadvantage: no load transfer, hardly any sound insulation, internal heat storage capacity, or summer heat protection

3. Air layer: Function => moisture protection of the thermal insulation through decoupling, summer heat protection through ventilation, thermal insulation through a resting air layer

4. Outer shell: 11.5 cm clinker as facing brickwork or sand-lime brick, etc. with plaster
Advantage: excellent, durable summer heat protection and weather protection, very good sound insulation, very good external heat storage capacity
Disadvantage: poor thermal insulation, no load transfer (which is not required)

The usual general contractors/general planners are mostly professionally and financially overwhelmed by this!

Best regards.

Hello €uro,

I appreciate your commitment regarding TGA, but sometimes I stand in disbelief at your (apparent) unwillingness to think a little outside the tunnel.

This necessarily leads to a multi-layered AW structure, where each layer takes exactly the part it can fulfill especially well.

That is "your" point of view... what you overlook is that there is no "one" exterior wall structure for every construction project. For example, a single-family house without many slender supports in the facade (the majority of construction projects) can very well be realized with a monolithic wall structure. On the other hand, a single-family house where a lot of concrete (statics) is required in the facade is often better equipped with full thermal insulation. It is, as always, also a question of economic efficiency.

Some time ago, I found an article from 1986, which really speaks to my soul. However, this essay only reflects “my personal” view of the requirements in construction; logically, I try to realize monolithic construction (whether aerated concrete or perforated brick) in the majority of cases, even if that often results in "cheerful" discussions with our architects. Because: full thermal insulation always protects against discussions with homeowners ... and apparently also with TGA planners.

"Around a stone lying in the snow, a snow-free space soon forms when exposed to sunlight, because due to its relatively low specific heat capacity, the stone quickly reaches such a high temperature in the sun that it melts the surrounding snow. Tibetan mountain farmers exploit the heat radiation absorption effect with dark-colored stones, animal dung, and clods of earth to free their deeply frozen soils on this roof of the world earlier from the warmer reflecting and insulating snow masses during the very short growing periods between sowing and harvest.

About two-thirds of this free, energy-rich, short-wave global radiation is absorbed or reflected by the Earth's atmosphere. However, the air layer is transparent enough to enable human, animal, and plant life in various climatic regions and habitations with sufficient radiant heat. Misguided highly insulated, immaterial spun or foam constructions (with an air pore volume of up to 98%) can absorb and store almost none of this freely offered heat due to the lack of mass. If it were physically possible, some "polystyrene scientists" in the industry might want, by legislation, to completely exclude all tempered building substance, such as the respective night-facing, sun-shielded, radiation-screened side of a hemisphere of the Earth. Fortunately, planets have the ability by rotation and migration to always expose all surface areas periodically to the light-radiating, heat-giving central body of our solar system, the sun.

Insulated wall constructions, such as highly porous "cardboard type constructions" as well as combinations of light and heavy component constructions, are location-bound, immovable, irreparable! When solar radiation strikes the surfaces (non-transparent) of insulation-free solid (and liquid) matter, on continents (seas) and on massive dwellings, it is converted into long-wave thermal (radiation) heat, which warms the Earth (and consequently the Earth’s atmosphere) and, with each increasing radiant heat level (e.g., from minus 7°C to minus 6°C) of the outer layers of thick exterior walls (monolithic and heated building substance), reduces the temperature difference between the inside and outside wall surface temperatures or the typically existing heat losses to the outside overall. Therefore, exterior walls should already insulate due to their thickness, but, as was common before, also be receptive to (global) radiation on both sides by their heavy mass with low specific heat capacity and thus be heated for free(!).

"Full insulation systems" block this "gift from heaven." Since mid-October 1983, everyone can officially read this in a short report of an energy consumption analysis and comparison of monolithic and porous construction methods ("in the open air") quasi "forced" by the brick industry. This short report, whose publication was delayed for more than a year, amounts to an "admission" by the Fraunhofer Institute that they have provided the construction industry via the Information Center for Room and Building or through publications with completely false, estimated energy savings values for highly porous exterior walls for decades, possibly more than 300% (perhaps up to 600%) too high.

An example from this report: A building with an applied insulation material of 23 (!) cm thickness on one exterior wall and an overall "energy world champion k-(insulation)value" (a common advertising slogan e.g. from the company "Isorast," who supply "back pain free" building blocks made from the BASF product "Styropor"), thus with a heat transfer coefficient of only 0.16 W/m[SUP]2[/SUP]K, has a significantly higher (!) heating energy consumption than, for example, perforated brick masonry with a three times "worse" k-insulation value of only 0.46 W/m[SUP]2[/SUP]K, even during a cold and radiation-poor measurement period in the "ice moon" January 1983!

From this hitherto endorsed but absolutely false difference in k-value data, still every energy expert molds the "softener" of their clients towards "full thermal insulation," disregarding the low service life and quality of these insulating wall constructions, as they calculate a roughly 70% lower heat loss at the respective insulated component and also about 4.5 liters less heating oil demand per m[SUP]2[/SUP] exterior surface and heating period on the basis of this "better" k-value of 0.30 W/m[SUP]2[/SUP]K determined according to legal calculation specifications. One must wonder how much longer – not to mention the aerated concrete foam producers – the 32 market-dominant "Poroton" major manufacturers want to continue “blowing” the plastic polystyrene into the biologically valuable, healthy clay or loam in spherical form, producing a misguided insulation material, the monoprodukt "Poroton T" (the T stands for tempo), mainly with cavernous cavities instead of well-drying hair-tube shaped pores (capillaries).

The strategy of Poroton management and the advertising council should soon be abandoned due to false standards, initially still relying on materials and (with regard to production) heating energy-saving reasons as well as weight-related reasons on insulation materials that are just still hand-carryable and to be preferably mortared in large formats, to the energetic disadvantage of the prospective homeowners and also at the expense of the competing small full-brick bakers, finally closing their "Tante-Emma shop" to possibly then take over the rare, valuable clay pits. It is well known that 36.5 cm thick exterior walls due to numerous previously mentioned properties made from (unfortunately only available in smaller sizes, e.g. 240/115/71 or 240/115/113 mm) full bricks (e.g. 1600 kg/m3) are the honest energy savers and above all, compared to porous bricks, indisputably indispensable for health reasons.

The fantastic laboratory thermal insulation values of "thermal protection according to DIN 4108" only refer to dry values, but (porous) building material shows hardly any sufficient thermal insulation after moisture uptake and has nothing to do with the prescribed heat demand calculations for building approval, for which only the calculation values for dry materials may be used(!), whose optimal laboratory theoretical values due to wetting after installation no longer bear any relation whatsoever to reality once the water balance in the wall structure begins.

Furthermore, besides the calculated heat storage and insulation values of the building materials, the resistance to water, vapor, and external mechanical influences also plays a role, for example that of full bricks or wood compared to insulation materials. It should be added that the hygroscopic water balance dependent on the respective meteorological humidity (air) in bricks, unlike other highly praised modern building materials such as sand-lime brick, pumice, gas, expanded, and normal concrete, is negligibly small, that further the full brick (not clinker brick) also shows a low vapor diffusion resistance and especially a good capillary moisture transport capacity (outwards in winter) compared to almost all types of concrete, and that bricks thus dry out faster and emit heat better than other highly praised masonry bricks that absorb water predominantly faster through vapor diffusion and driving rain than they release it again.

The desorption, e.g., in bricks is about ten times as high as in sand-lime bricks. A good capillary capacity of the masonry bricks, the joint mortar (preferably lime plaster and without chemical sealing additives), and the coatings is thus necessary for transporting construction moisture or water vapor condensate to dry both the entire cross-section of the enclosure walls and the indoor air to the tolerable level of 40-65% relative humidity, which when using modern vapor-tight building materials, films, and current insulation wall constructions is only still possible via window ventilation causing the usual rapid heating energy losses, excluding any heat storage capacities in the exterior walls. Although the improvement of indoor air due to gas exchange between inside and outside through this "breathing" of brick walls may be quantitatively very marginal, the qualitative regeneration of the indoor air is of significant "building biology" relevance, in which the brick exterior walls, on their inner surfaces (usually cooler than indoor air), transport the off-gassing of inhabitants, pathogens, transpiration from skin or other "pores" of humans, animals and plants, bacteria, and mold spores through the vapor diffusion and capillary moisture transport properties of this building material through the exterior wall outwards, disinfecting the harmful bacteria etc. by the lime components of mortar and paint coatings, which otherwise would swirl around with dry dust in heated rooms.

Insulation wall constructions – whether insulated on the outside, inside, or at the core of the wall structure – remain unresolved climate shells, which always lead to visible and above all invisible moisture damage and the resulting hidden energy losses. Sufficiently thick solid walls with uniform structure barely know these problems and are honest energy savers! The legislative insulation requirements of heat demand and vapor diffusions simply do not correspond with the given natural sciences. And isn't this flood of one-sided insulation advertising brutal enough to let every truth about the real annual heat balance losses "sink"? Isn't it an absurdity that after the thermal protection ordinance came into force on January 1, 1984, owners of massive building substance, for example during renovations, are even legally "forced" to spend money on additional thermal insulation, the supposed insulation miracle, in order to, after this renovation-required misinvestment, in fact consume more energy costs!), because their old massive, heat-storing undamped buildings are "toweringly" superior to everything else in both energy consumption and living and usage quality?

Because it is well known that an insulated thermos bottle not only can keep coffee hot but also prevent ice cubes from melting, so many "insulated" homeowners have to heat in June! Moreover, insulating materials, such as at least UF foams, must be classified as hazardous to health and mineral fibers (fiberglass, slag wool, and rock wool) as suspected carcinogens due to their respirable fiber shape. Therefore, I hereby announce an end to the previous lightweight construction methods at least for residential buildings, a nemesis for insulating wall constructions. In the Federal Republic of Germany, only passenger cars, spaceships, or the like will be insulated against cold and heat for weight-related reasons. [I]However, residential house walls will be built again thicker, solid, and without insulation, vapor diffusion-capable without vapor barriers and thus naturally and healthily."

Source: A. Klaus/Arch+

My conclusion: how foresightedly written; with 36.5 and 42 cm wall construction we are already there... even if admittedly forced by Brussels

Regards, building expert

...., only sometimes I stand incredulous before your (apparent) unwillingness to think a little to the right and left of the tunnel....

Accusing me of unwillingness is probably influenced more by your sales-related, therefore predefined boundary conditions, only a knave might think ill of this!

- as always - also a question of economic viability....

Correct, therefore bargain hunters always initially choose the cheap option, without knowledge of the lasting and sustainable, actual economic viability! Cheap at the beginning usually becomes very expensive in the end!

Because: ....

...No own, professionally justified opinion present? Dependent on assistance from vague salesmen? In the case of study results, a simple piece of advice often helps: Who initiated these and who sponsored the results?! This actually sufficiently explains the presentation of the results! Only duds and naive people base a significant investment decision, which accompanies them for 20...25 years, on professionally completely undefined sales offers!

Best regards.

Hello €uro,

I should have known better; you don’t handle headwind very well

Accusing me of reluctance is rather influenced by your sales-related, therefore predefined boundary conditions, [...]!

This impression inevitably arises without any further effort.

Correct, therefore bargain hunters always initially choose the cheap option, without knowledge of the long-term and sustainable, actual economic efficiency! Cheap at the beginning usually becomes very expensive in the end!

This statement – although in the sum of the respective BCs of so-called bargain hunters true – has absolutely nothing to do with the issue under discussion.

...No own, professionally justified opinion available? Dependent on assistance from diffuse sellers?

I posted this text exclusively as a reflection of my thoughts on the subject of insulated AW versus monolithic construction. I have no intention of constructing the jack-of-all-trades from it ... neither professionally justified; nor reinventing the wheel.

With study results, a simple piece of advice usually helps: Who commissioned them and who sponsored the results?!
That basically explains the presentation of the results sufficiently!

Have you already had the idea that by this you are implicitly claiming that only your opinion – which you surely consider unbiased – may be accepted as the gospel truth?

You don’t necessarily make an exchange with you easy if you always retreat to your calculation methods – how am I supposed to follow you there, since I am not an engineer? Especially since you are in no way willing to make your results publicly and, above all, free of charge, comprehensible for the benefit of the users of this forum? You hide behind numbers/formulas? Or, on the other hand, deny that – quite simply – it is not the end of the world to accept a different opinion as such? You always react in the same pattern when a response is before your eyes that does not fit into your way of thinking – namely, in my view, inappropriate and in my opinion unworthy of your reputation – like a pubescent teenager responding?

You may be many things; a congenial character probably isn’t one of them.

Rhineland greetings

You don't necessarily make an exchange with yourself easy if you constantly retreat to your calculation methods - how am I supposed to follow you there, since I am currently not an engineer? Especially since you are in no way willing to make your results publicly and above all freely available for the benefit of the users of this forum in a comprehensible manner? Hiding behind numbers/formulas?

That is exactly the problem with 99% of the €uro contributions. Users ask very specifically, the answer is usually:

"Blah blah.... have you already considered ? blah blah.... And anyway, can’t be correct at all. ...blah blah... therefore the concept is total rubbish. You should definitely consult a building service engineer.

Best regards

<Signature promoting one's own building services>

€uro, you write a lot and - if one is to believe your postings - you also know a lot, but I have NEVER read anything concrete from you. Why don't you post 2-3 example calculations of energy certificates, which according to you are so often wrong? Why no homepage showing your references?

It would be nice if the next 1400 postings became more productive.

Thanks and regards klblb