Ventilation system in the new building, yes or no?

So, the way I read this here, a house with 30 cm Ytong exterior wall and 6 cm insulation (Primary energy demand 60.2 kWh/m²/a) should have a ventilation system????

Sorry, but such nested sentences with multiple subordinate clauses and several brackets do not necessarily lead to better understanding. @Bauexperte: could you please write it again more clearly? For example, we will have a single-layer exterior wall (T10, 36.5cm or T9 36.5) and KfW70 standard. In addition, the new heating center from AI (air heat pump, hot water, and controlled residential ventilation).

Hello,

So as I read this here, a house with a 30 cm Ytong exterior wall and 6 cm insulation (primary energy demand 60.2 kWh/m²/a) should have a ventilation system????

This is advisable if the house receives ETICS.

Kind regards

Hello,

@Bauexperte: can you please write it more clearly again? For example, we will have a single-layer external masonry wall (T10, 36.5cm or T9 36.5) and KfW70 standard. In addition, the new heating center from AI (air heat pump, hot water, and controlled residential ventilation).

Simply put: as soon as a masonry wall with thermal insulation composite system (WDVS) along with synthetic resin plaster as a finish is constructed, a ventilation system is recommended in any case. The masonry is usually so airtight with such a structure that otherwise the risk of mold formation would be too high.

With the wall construction you prefer, controlled residential ventilation is not strictly necessary if you ventilate sufficiently; costs and benefits of heat recovery aside. How much "sufficient" means you will know once you have the result of the blower door test. Benchmark: the more significantly the permissible maximum value – which is 3.0/h for houses with window ventilation – is undershot, the more necessary regular ventilation through the existing windows is.

Best regards