Is a central ventilation system absolutely necessary?

If I understood correctly, the insulation is not decisive, since a 36.5-brick house without insulation or a comparable KFW-70 house is airtight. As long as one has the time and necessary discipline, the moisture can still be removed without a ventilation system by airing through the windows. But at a certain low-energy standard, the energy concept is so strongly designed to retain heat in the house that too much heat would escape through window ventilation, and the controlled residential ventilation with heat recovery then becomes necessary because of heat retention.

So for simpler houses, a controlled residential ventilation system is rather a comfort issue or necessary if one cannot ventilate often enough, and the more one moves towards a passive house, the more indispensable it becomes - right?

Hello,

I think it strongly depends on whether you build insulated or uninsulated. We want to build with 36.5 cm bricks WITHOUT insulation with KfW 70. The opinions of the last 3 developers were unanimous. About 90% of the houses built without insulation are built without a ventilation system, since it is not necessary for this type of construction. One developer even installed it in his own house but cannot recommend it if it is not necessary, as the air sucked in from outside becomes very dry in winter due to preheating.

That’s nonsense the providers told you; I assume they can’t sell added value. Whether with or without insulation, new buildings these days are so airtight that it is worth considering in all cases and in my opinion should be decided based on whether multiple daily ventilation intervals can be guaranteed in the first 2 years after moving in or not.

That is about as sensible as fighting dry air with damp laundry. Sometimes I can only shake my head at the resulting absurdities of the Brussels decisions.

Rhenish greetings

.....So for simpler houses, controlled residential ventilation is therefore more a matter of comfort or necessary if you cannot ventilate often enough, ....

Correct! How often do you actually have to ventilate, especially if, for example, there are no "moisture sources" affecting the building during the day!

...and the more you move towards a passive house, the more indispensable it becomes - right?

Correct! In a PH, internal and solar gains are significantly involved in the annual energy balance! Here the energetic effect of controlled residential ventilation is considerable, i.e., significantly higher than in an existing building or energy saving ordinance standard!

Best regards

Hello Kazazi,

we are mostly discussing new buildings here. The question of manual ventilation no longer arises after 2 years have passed. €uro's statement is therefore not correct, as there is indeed moisture present.

PH must not have heating; therefore, controlled residential ventilation with heat recovery is a must-have. And despite all the "paper- or formula-based" calculations - if no people live in the PH during the day, the clever calculations are useless; the place is cold.

Rhenish regards

Building expert, on the go

If no people live in the PH during the day, the clever calculations are for nothing; the place is cold.

Unless enough cats live in the place...

A controlled residential ventilation system with heat recovery is beneficial in any case. We have had many customers where the houses were contaminated with mold spores; these were new buildings where the builders had foregone a controlled residential ventilation system. The mold does not always have to be visible. The new buildings are simply too airtight.