Ventilation system with heat recovery - sense or nonsense?

But the supply air was not warmed by the exhaust air, but by the heat energy of the window, which you provide by heating the room. In contrast, a heat recovery system uses the energy in the exhaust air that would otherwise not be utilized.

Of course, I also know this rumor: "the Ytong® soaks up water". Put a aerated concrete block and a hollow brick in a tub full of water overnight; you will probably be very surprised. It is comparable to the equally persistent rumor: [I]"meat dissolves in Coca Cola®"[/I]

I imagine it more like this, construction expert:

I put a hollow brick and an aerated concrete block in water for weeks/months... then I put both in the sun for a day. The hollow brick is dry afterward, the aerated concrete block still contains residual moisture because it does not release it as well...

I am not talking about problems with moisture ingress in aerated concrete during "regular residential use," but rather that it takes a little longer until the initial construction moisture is out of the block.

Styrofoam is also not suitable for use in standing water, since over time the "beads" fill with water and the thermal insulation effect is lost... but if I put Styrofoam in water overnight, I still see no effects...

But the supply air was not heated by the exhaust air, but rather by the heat energy of the window, which you provide by heating the room. Heat recovery, on the other hand, uses the energy in the exhaust air, which would otherwise not be used.

I am aware of that.
However, since it is already clear to most that a central controlled residential ventilation system with heat recovery is not economical, ultimately only moisture protection and comfort remain.

Moisture protection is also provided by a decentralized exhaust air system, and the comfort is not as much lower as is claimed. It’s not as if I am opening a window at -5°C...

On the topic of moisture and aerated concrete, I read something interesting about this topic at Ytong. It says there that Ytong is completely saturated after 2-3 days in water and that it then takes 2-4 weeks until the moisture has dropped enough to correspond to the moisture exposure in a new building... that's all on this topic....

Now, however, comparable information for other "stones" is missing. That’s all.

Hello,

I'm wondering quite heretically whether your experiences possibly come from the fact that you mainly build with aerated concrete? I have often heard that AAC stores more moisture during the construction phase and does not dry out as quickly. The requirements for the ventilation behavior of the occupants are therefore stricter, especially in the first 1-2 years...

I just wanted to add a few words to my answer to you without technical jargon, pressed the wrong button and lost it; it can happen... so here we go again, without technical jargon.

I do not find your question heretical

As I keep writing, there is no “the” ultimate stone; each has advantages and disadvantages. For example, masonry made of fired bricks shrinks and creeps in general, especially with walls made using thin-bed mortar. Sand-lime bricks don’t even come close to good thermal insulation properties. And aerated concrete is highly capillary-active due to its small pore structure, i.e., when water meets a component made of aerated concrete, this material—although delayed—absorbs more water, meaning relatively large amounts of water can be stored in the structure.

That is why careful processing of the material is particularly important, and adequate protection against penetrating rain on all aerated concrete component surfaces must be ensured at all times during shell construction.

However, the advantages of this building material cannot be denied.

[*]Wide variety of dimensions: aerated concrete can be produced in many different sizes – from standard blocks to large reinforced panels
[*]Excellent thermal insulation: aerated concrete has an extremely low thermal conductivity, which results in high thermal efficiency. This means a significant potential for saving on heating and cooling costs
[*]Extremely lightweight: aerated concrete weighs about 50% less than other comparable building materials
[*]High compressive strength: aerated concrete is a solid product and therefore extremely load-bearing. The entire surface is included in the structural engineering calculations
[*]High dimensional accuracy: due to its dimensional accuracy, aerated concrete is very easy to work with since no thick mortar is required
[*]High sound insulation: the porous structure of aerated concrete provides high sound insulation
[*]High fire resistance: aerated concrete has an extremely high fire resistance of at least 4 hours and more
[*]Termite-resistant: aerated concrete cannot be damaged by termites or other insects
[*]Good workability: thanks to the excellent size/weight ratio, building with aerated concrete is very fast
[*]Recognized as an ecological building material

Even though aerated concrete loses to sand-lime brick in terms of soundproofing, this is negligible in times of 36.5 cm exterior masonry and more.

Recently, we have also worked a lot with hollow bricks. Apart from the fact that careful processing of the material is important for other reasons, I also find here that it simply does not work without ventilation. Especially not when an ETICS has been applied; which— and this probably closes the circle —also equally applies to all other stones.

Rhenish greetings

Hello,

I imagine it more like this, construction expert:

I put a hollow brick and a aerated concrete block in water for weeks/months... then I put both in the sun for a day.. The hollow brick is dry afterward, the aerated concrete block still contains residual moisture because it does not release it as well...

I would like to endorse that

Rhenish greetings