ᐅ Poroton or lime-sand brick

I have aerated concrete in my exterior wall and all interior walls are made of 24cm (9.5 inches) sand-lime bricks. Algae growth is a common issue with any high-insulation method, whether using masonry or an external thermal insulation composite system (ETICS / EIFS). The problem occurs because the exterior surface of the walls stays cooler since less heat escapes from the inside, causing moisture in the warm air to condense on the surface, which leads to algae growth. I experience this problem as well, but only on the north-facing wall where no sunlight warms the brick, even though I do not use ETICS but aerated concrete blocks.

Thank you, that is valuable information, as I had always assumed that the problem only occurred with ETICS.

One more question – how do the two solutions compare in terms of summer heat protection?

"Irrelevant," since you’re letting the heat in through the windows.

In our case, it’s extremely noticeable, with almost black tiles behind glass. One day on the sunny side without shutters down, and the result is 28°C (82°F).

If you seal the house completely (shutters down from 6 a.m. on the sunny side), the interior stays at a cool 23°C (73°F). Just don’t open the door, or you’ll be overwhelmed by the heat.

Completely irrelevant? We currently live in a prefabricated / timber frame house (13 years old), and the heat definitely does not come in only through the windows.

However, we are talking about a new build made of sand-lime brick or Poroton. Not a 13-year-old prefabricated wooden house.