ᐅ Exterior wall with ETICS or exterior wall with lightweight render?

Great.. thank you very much..

And regarding issues like mold, moisture diffusion, etc... is there a difference there? Is a ventilation system recommended????

Yes, a ventilation system is definitely recommended because no matter how you build, moisture will not simply disappear through the walls.

Of course, you can ventilate several times a day, but that means opening windows fully on every floor for several minutes... but who can realistically do that nowadays? Humans, plants, and so on add extra moisture to the house daily, in addition to the moisture from construction. If heating is insufficient and there is only limited air exchange (such as tilted windows), problems will start to occur, because modern houses are practically like plastic bags (which is not necessarily a bad thing).

So, as I said, nowadays I would neither buy nor have a house built without a controlled mechanical ventilation system.

Hello Marcel,

I would not reduce the difference between the two construction methods to a purely philosophical level; in my opinion, they differ significantly in terms of building physics and construction technology as well.

malu82 schrieb:
24cm porous hollow brick plus 8.0cm (3 inches) insulation (polystyrene rigid foam boards), reinforcement layer, and finish plaster

Here, you are essentially building a second house around the brick structure: one made of styrofoam. I am deliberately avoiding the philosophical views on this topic to prevent widespread debate and fundamental discussions. Simply the fact that, unlike a "normal" house where the finished walls receive plaster, here an additional structural layer of various materials with considerable thickness is added, increases not only the effort but also the potential for errors and problems proportionally.

This includes many additional work steps (fixing the insulation, closely fitting the boards without gaps, more complex reinforcement, very critical selection of the plaster, constructive consideration of the 8cm (3 inches) thick assembly at window sills, roller shutters, etc.) as well as additional issues in the later life of a styrofoam façade (holes from woodpeckers and others, damage from leaning bicycles, possible moisture and insect ingress into defects or behind the boards in case of faulty installation, risk of algae growth on the façade, flaking due to normal weathering over the years, etc.).

Just walk through the streets with open eyes, look at styrofoam façades that were installed a few years ago using adhesive and dowels, and judge for yourself. Sometimes personal observation helps a lot in making decisions.

malu82 schrieb:
36.5cm porous hollow brick and 2.0cm (0.8 inches) lightweight plaster with fabric mesh reinforcement.

With a few centimeters (inches) thicker brick, you avoid all the above additional problems. The façade work is limited to setting plaster profiles, embedding the reinforcement, and then applying the plaster to a total thickness of 2cm (0.8 inches). That’s it.

The plaster should be precisely matched to the brick to optimize temperature distribution and the dew point within the system. Lightweight plaster / insulating plaster is also available with purely mineral additives, so you can completely avoid using styrofoam—even in powdered form—if you wish. The plaster regulates stresses, moisture, and weather exposure in a layer thickness of 2cm (0.8 inches)—not in a few millimeters like the plaster on ETICS systems—also providing protection against possible woodpecker or bicycle damage. I am deliberately not giving a value judgment here but simply listing the facts.

Best regards

@Allrounder:

You should also mention that plaster flaking can occur on both monolithic and ETICS (External Thermal Insulation Composite System) facades. Algae growth is not limited to ETICS facades but can also appear on monolithic walls. In practice, the likelihood is just as high at the same U-value. Algae don’t care what material is underneath the plaster. 😉

@DerBjoern:
Of course, a monolithic construction method does not exclude the possibility of algae growth.

However, with external thermal insulation composite systems (ETICS), this unpleasant phenomenon occurs much more frequently and also much faster (Source: Fraunhofer Institute for Building Physics, I am not allowed to provide the link). The issue is nocturnal condensation, which promotes algae growth—much less so general precipitation exposure. Especially on north-facing façades, the surface temperature of ETICS can drop below the outside air temperature at night, which does not happen with monolithic walls. In the latter, the wall temperature does not fall below the outside air temperature. This quasi-supercooling of the wall—a phenomenon specific to ETICS—leads to condensation and increased algae growth.

Next time you go for a walk, try counting the algae-covered walls on both ETICS and monolithic walls (excluding cases with structural faults like damaged roof drainage, insufficient roof overhangs, sill overhangs, etc.). Even a layperson will notice that many houses retrofitted with thermal insulation now shine in a brilliant green on their north sides... 😀

The fact that monolithic walls do not develop algae is due to the lower U-values of the walls in PRACTICE.
Although the plaster in external wall insulation systems (EWIS) cools down faster, it also warms up again more quickly.