Walls made of aerated concrete

Of course, you can also build monolithically with Poroton. With 48 cm Poroton you exceed all requirements – with 36.5 cm you fulfill them.

But the plan is aerated concrete, or did you make a typo? By requirements, do you mean the legal demands? But whether that is good or not is the next question.

Yes and no – Poroton also doesn’t have a much better sound insulation value than aerated concrete. KS (calcium silicate) to some extent does. There are also some construction companies that therefore build interior walls from KS. (The heavier, the better the sound insulation – best to look at the datasheets)

Ok, then I’ll ask how the interior walls are done, whether it might be better to execute them in KS. I suspect that the standard choice is aerated concrete because it is probably easier to work with (especially when it comes to chasing – right?)

It’s certainly a gain in comfort. I lived in 2 rental apartments in the last 3 years that were already more or less "airtight" (although from 1997 and renovated) and every time I entered them, a blast of stagnant air hit me.

We are also currently living in a “dead insulated” old building. Especially in winter, it’s really exhausting to ventilate enough (but it works). But I see it as even easier in the 3-room apartment than in a house with a utility room where moisture certainly arises but no window is present, or in the guest room which is rarely occupied. So, you recommend it as well?

Again the thing with mass – the heavier, the more inert (the more heat or also “cold” a stone stores). In KS it takes longer to heat up. Another aspect is the phase shift, basically the point at which the heat arrives inside the house. If this is, for example, 14 hours, the midday heat arrives at night indoors. Go into a church on a hot summer day – similar idea. Without shading and during long-lasting heat periods, though, this also has its limits.

Ah okay, that of course slowly makes sense again. Thanks.

I think it depends on how you see it… whether 14 cm wool or 16 cm from the hardware store doesn’t make much difference – but if the supplier wants to find your price point and then stages the price in 2 cm increments with hefty surcharges, it certainly does. If you plan to stick external insulation on your Poroton, that is generally not worthwhile.

As I said, it’s supposed to be aerated concrete. But if I understood correctly, you also confirm the opinion that extra insulation on aerated concrete is not economical, right? (I simply assume that Poroton or aerated concrete doesn’t make much difference here).

That is a good goal and you can achieve it quite well with 42 cm walls without additional insulation. That includes roof, windows, and basement ceiling/floor slab, everywhere you should target U-values of 0.17–0.2, or windows max. 0.9 W/m2K. The heating system should integrate 15% renewable energy – ultimately you need someone to do an energy saving regulation calculation for your house to prove the achieved standard. Then you know exactly which wall thickness and which brick is right for you. The energy saving regulation calculation is needed anyway for funding and building application.

If you apply this year, you will still get funding, KfW just announced that starting April 2016 the Efficiency House 70 standard will disappear as a funding standard.

Thanks for the hints. Well, the current plan is only a 36.5 cm wall thickness. Windows will of course be triple glazed. The roof and floor slabs will be insulated. I don’t know the U-values yet, I have to get them. Currently, only a solar system for domestic hot water is planned. I would have liked a geothermal heat pump, but I think slowly that I can’t justify the higher costs versus the gas condensing boiler in the long run.
So with 36.5 cm aerated concrete without additional insulation and gas condensing boiler + solar, it probably won’t be enough, right? Rough estimate. Oh, and a controlled ventilation system will presumably be installed because, as written above, I find it hard to ventilate everything properly by hand… Even if you always hear horror stories about “disease-causing controlled ventilation systems.” I can’t assess that yet either.

No reasonable construction company would even consider that.

So you mean the partition wall to the neighboring house shouldn’t be made of aerated concrete? How about the homogeneity of the wall if I let one wall be executed in KS? I understood it that all walls, including the partition wall to the neighboring house, should be made of aerated concrete (according to the offer). And a silly question, how does a wall in aerated concrete compare in price to KS or Poroton?

Hello,

Soundproofing boards are to be installed between the wall and the neighboring house.

And what is that supposed to be?

I have to admit first of all that I am quite a layman

So they do exist – engineers who know that they (outside their field) know nothing.

I just can’t grasp what a difference of 0.1W/(m²K) really means in reality.... I lack the imagination/practical experience for it.

Neither can I; it’s just another numbers game in the context of advertising.

- Aerated concrete can be built without additional insulation. But is it any good!? Is it just enough to meet legal requirements or does it also make sense to build that way?

We have been building monolithically for years; optionally with aerated concrete or Poroton. Meeting legal requirements requires more than just choosing a material.

- Aerated concrete has worse sound insulation than limestone or Poroton. Which could be problematic especially with thin interior walls.

That’s why many suppliers who build with this material offer interior walls in the attic as lightweight construction. Not a few builders also choose limestone. I always wonder why limestone is chosen – were potential builders so disturbed by the “noise” from children in their previous rented apartments, or is it rather trendy to hop on the supposed “noise pollution” bandwagon?

- Whatever I build (even without extra insulation layer) a controlled residential ventilation system is strongly recommended because the houses are all very tight.

I see it the same way; yes – the upcoming Energy Saving Ordinance 2016 will further promote this. If you read the forum posts here on the topic of controlled residential ventilation, you will see that controlled residential ventilation "also" brings a great gain in comfort. Whether central or decentralized is one of the “Jehovah topics”.

- Aerated concrete has poor thermal insulation properties in summer (but I still don’t understand why a stone supposedly insulates well in one direction – in winter – and supposedly not in the other – in summer –?!)

Because anyone can write whatever nonsense they want on the internet.

Due to the many small air pores, aerated concrete has very good thermal insulation. The low thermal conductivity ensures that as little heat as possible is lost to the outside in winter. Conversely, it ensures in summer that the interior remains pleasantly cool despite high outside temperatures. So there is a comfortable indoor climate throughout the year.

However, if we have temperatures above +30°C in Germany for a while, only an air conditioner helps. We have 40 cm bricks (old building) and sweat just like anyone else.

- I have often read that the costs for applying additional insulation to a wall do not amortize over a reasonable time (regarding heating savings – of course, that also depends on the heating technology).

If insulation, then you should, in my opinion, consider the type of insulation. And yes – more does not necessarily mean less heating cost; that requires controlled residential ventilation.

Can you help me out where I am wrong? Why is limestone always recommended for interior walls instead of aerated concrete? Sound insulation? Less crumbling when drilling? Price?

“That’s how it’s always been done, we have always done it that way” – people who make such statements always forget, among other things, that no stone works without special screws/dowels. Otherwise, I wrote something about this topic above.

Is the omission of additional insulation really “state of the art” and sensible (not cost-effective regarding heating costs) or just cheap?

What should be problematic with a 36.5 cm stone regarding soundproofing? I, by the way – personally – consider aerated concrete + ETICS as a “cheap” solution. It is price-neutral compared to monolithic wall construction – at least it should be – but is often chosen by builders because external settlement cracks can be nicely hidden behind the facade.

Which wall structure would you recommend and why given the above conditions?

Only you can make this decision; there is no “better” or “worse” offer regarding exterior walls. There is not “the” stone, if there were, the world would be pretty monotonously colored. It depends on many factors – location of the construction site in Germany, seismic zone, soil conditions, to name just a few. And also on the budget – a concrete facade wrapped in styrofoam is cheaper than a monolithic exterior wall.

Rhenish greetings

So you mean the partition wall to the neighboring house should not be made of aerated concrete? What about the homogeneity of the wall if I have one wall made of KS?

If the common wall has the same thickness 36.5 - to the detriment of the living space - as the other exterior walls, it is not a problem. Otherwise - I once "borrowed", saves me typing

"The common wall must not only fulfill the function of sound insulation and fire protection, it is also an indispensable part of the load-bearing structure of both adjacent buildings, which is why a common wall must remain in its original place even if the neighboring building (for whatever reason) is no longer present in its original form, for example due to demolition, alteration or even a fire event. This also illustrates the particular problem of a common wall: it is basically the property of both homeowners, whose apartment or building partition wall is single-layered. Another major problem is usually insufficient sound insulation, because the common wall, especially in older buildings, is usually not made of sufficiently heavy building materials (e.g., solid brick or heavy concrete blocks) and often has pipes (for water and sewage) embedded in the wall that further impair the sound insulation.

Fire protection of a common wall is also not without problems. To prevent or at least delay fire spread from one building unit to the immediately adjacent unit, no combustible materials (such as wooden purlins) may be embedded or even passed through the common wall (although this is often the case). Also, slots or recesses for water pipes and even larger sewage pipes reduce the resistance of the common wall to fire effects. Renovation measures can also lead to further weakening, for example by installing electrical and/or heating distribution in the common wall. This not only significantly reduces the fire resistance duration of the common wall but also noticeably worsens the sound insulation."

And a silly question, how do the prices of an aerated concrete wall compare to KS or Poroton?

An answer to that won't really help you, as every supplier/BU/GU handles it differently


**Source: LKG Fachbegriffe

Rhenish greetings

And what is that supposed to be?

Well.... I would have to ask about that.

So they do exist – engineers who know that they (outside their field) know nothing

Of course... "Know that you know nothing"

Me neither; it’s just another numbers game as part of advertising.

Hmm... ok, that doesn’t make it any easier for me If not even the professional can pinpoint it exactly, I don’t even have to try.

We have been building monolithically for years; by choice with aerated concrete or Poroton. Meeting the legal requirements needs more than just choosing a material.

OK, and I assume you have good experience with that. I still have in my head how years ago everyone started like crazy to wrap their houses in styrofoam. And today, where the requirements and wishes have progressed clearly, is it suddenly no longer necessary? I didn’t think the bricks had undergone such an evolution.

That’s why many providers who build with this material offer interior walls in the attic as lightweight construction. Quite a few builders also choose KS. Whereas I always wonder why KS is chosen – have potential builders been so disturbed by the "noise" of children in their previous rental apartments or is it rather hip to jump on the supposed "noise pollution" bandwagon?

To be honest, I don’t quite understand that. Why do they then build the attic with lightweight construction? Well, I just thought that the sound insulation of modern houses is rather worse than in older buildings. And if you turn up the amplifier, you don’t want the neighbor standing right at your door... Otherwise I could just stay in an apartment. As far as I’ve been told, no sound insulation has yet been invented against children screaming.

I see it this way; yes – the upcoming 2016 Energy Saving Ordinance will further promote this. If you read the posts on the controlled residential ventilation topic here on the forum, you will realize that a controlled residential ventilation also brings a big increase in comfort. Whether central or decentralized is one of the "Jehovah topics"

Yes, I suspect we won’t get around it anyway. Without heat recovery it probably doesn’t make much sense, does it?

Because every fool can write whatever he wants on the internet.

Due to the many small air pores, aerated concrete has very good thermal insulation. Its low thermal conductivity causes that as little heat as possible is lost to the outside during winter. Conversely, it ensures it remains pleasantly cool inside even despite high outside temperatures in summer. This results in a pleasant indoor climate throughout the year.

However, if we have temperatures over +30°C in Germany for a while, only an air conditioning unit helps. We have 40 cm bricks (old building) and sweat just like everyone else.

Ok, that’s reassuring to hear.

If insulation, then in my opinion you should deal with the type of insulation. And yes – much more doesn’t necessarily mean less heating costs; that requires controlled residential ventilation.

Ok, I have nothing against doing without insulation if I’m sure I’m not building a garden heater.

"It was always like that, we have always done it that way" – people who make such statements always forget, among other things, that no stone works without special screws/dowels. Otherwise, I wrote something about the topic above.

Now you’re saying something.... When I imagine hanging a kitchen cabinet on 11 cm aerated concrete, my knees get a little shaky... But people tend to underestimate walls and anchors.

What should be problematic about a 36.5 cm stone in terms of sound insulation? I, by the way – personally – consider aerated concrete + ETICS as a "cheap" solution. It is cost-neutral compared to monolithic wall construction – at least it should be, but it is gladly chosen by builders because external settlement cracks can be so nicely hidden behind the facade.

OK, the offered company does not want to use ETICS. The sound insulation concerns me especially regarding the interior walls. Because, as I said, if it’s only an 11 cm wall... No idea if that insulates much.

You alone can make this decision; there is no "better" or "worse" in the offer of exterior walls. There is no "the" stone, if there were, the world would be quite monotonously colored. It depends on many factors – location of the building site in Germany, earthquake zone, soil condition, to name just a few. And also on the wallet – a concrete facade wrapped in styrofoam is cheaper than a monolithic exterior wall.

OK, thanks. Then the only remaining question for the exterior walls is whether the wall to the neighboring house needs to be designed differently....

If the partition wall has the same thickness 36.5 - to the detriment of the living space - as the other exterior walls, it is not a problem. Otherwise - I once "borrowed", saves me typing

Ah OK. Yes, it would be (as far as I understand) a completely normal exterior wall like all the others. Also, the two houses each have their own walls (so no shared wall). Then I don't have to worry about it. Thanks

OK, and I guess you have good experiences with it.

Yes. I would never voluntarily apply an ETICS made of OIL; but that is my very personal view and by no means the only valid one.

I still have in mind how years ago everyone started crazily wrapping their houses in styrofoam. And today, when the requirements and wishes have clearly progressed, suddenly it is supposed to no longer be necessary? I didn't think the bricks had undergone such an evolution.

The houses you describe were mostly built in a hurry after the war. Exterior walls (EW) of 12 or max. 15 cm thickness were not uncommon. If the chimney was replaced by central heating in the early 70s, the owners might as well have thrown their money out the window. To prevent this – and with subsidies – the oil processing industry has made itself quite healthy.

I honestly don’t quite understand that. Why do they then build with lightweight construction in the attic? Well, I just thought that the sound insulation of modern houses is rather worse than in older buildings. And when you turn up the amplifier, you don’t want the neighbor standing right at your door... Otherwise I could just stay in an apartment.

You can – you should – not combine all materials (different drying behavior). That is why the providers – including myself – resort to lightweight walls in the attic. They have many advantages, especially better soundproofing (separating the bedrooms). Furthermore, they can later – when the little ones have left the house (usually faster than expected) – be removed more easily and with little mess, allowing a new room layout.

But aerated concrete in combination with porous concrete is less critical; therefore this combo is also suitable.

I’ve been told that no sound insulation has yet been invented against children’s shouting.

Exactly.

Yeah, I guess we won’t get around it anyway. Without heat recovery, it probably doesn’t make much sense, right?

If you want to stay with gas, it will probably come down to that in my opinion. Regarding the so-called recovery, I’m not sure (though I’m no engineer) whether it is mostly proven only on paper by calculation. But you will probably need it for the Kfw 70 standard.

Now you say something... When I imagine hanging a kitchen cabinet on 11cm porous concrete, my knees get a little shaky... But walls and anchors are often underestimated.

With the right anchor, that’s no problem.

Ah OK. Yes, it would be (as far as I understand) a completely normal exterior wall like any other. Also, the two houses each have their own walls (so no shared wall). So I don’t have to worry about that. Thanks

I can hardly imagine that; better ask explicitly again!

Usually, communal walls made of KS (lightweight concrete blocks also work) are built on both halves; between these walls is then an air gap of about 4 cm. The "usual" EW thickness (36.5) is generally omitted since it would reduce the already small buildable area for a semi-detached house. Normal EW thickness is only chosen where it cannot be reliably determined whether the second semi-detached partner will also build in the foreseeable future.

Rhenish regards