ᐅ Is a Central Ventilation System Really Necessary?

If I understand correctly, the insulation is not the main factor, since a 36.5-brick house without insulation or a comparable KFW 70-rated house can still be airtight. As long as you have the time and discipline, it is possible to remove moisture without a ventilation system by simply ventilating through the windows. However, at a certain low-energy standard, the energy concept is so focused on retaining heat in the house that too much heat would escape through window ventilation, making controlled mechanical ventilation with heat recovery necessary to preserve warmth.

So, for simpler houses, controlled mechanical ventilation is more a matter of comfort or a necessity if you cannot ventilate often enough, and the closer you get to a passive house standard, the more essential it becomes—is that correct?

Hello,

zovima15 schrieb:
I think it strongly depends on whether you build with insulation or without. We want to build with 36.5 cm (14.4 inches) brick WITHOUT insulation to KfW 70 standard. The opinions of the last three developers were consistent. Around 90% of houses built without insulation are constructed without a ventilation system because it is not considered necessary for this type of construction. One developer even installed it in his own house but does not recommend it if it is not needed, as the air drawn in from outside becomes very dry due to preheating in winter.

That is nonsense what the providers have told you; I assume they cannot sell additional benefits. Whether with or without insulation, new buildings nowadays are airtight enough that in all cases it is worth considering ventilation systems, and in my opinion, the decision should be based on whether multiple daily ventilation intervals can be ensured during the first two years after moving in or not.

This is about as logical as trying to fight dry air with wet laundry. Sometimes I can only shake my head at the resulting absurdities of Brussels’ decisions.

Regards, Bauexperte

Kazazi schrieb:
.....So for simpler houses, a mechanical ventilation system with heat recovery is more of a comfort feature or necessary if you cannot ventilate often enough, ....

Correct! How often does one actually need to ventilate, especially if, during the day, there are no significant sources of humidity affecting the building?

Kazazi schrieb:
...and the more you move towards a passive house standard, the more essential it becomes – right?

Correct! In a passive house, internal and solar gains play a significant role in the annual energy balance! Here, the energy performance of a mechanical ventilation system with heat recovery is considerably greater, or clearly higher, than in an existing building or a standard built to energy saving regulations!

Best regards.

Hello Kazazi,

Here we mostly discuss new constructions. The question of manual ventilation only becomes irrelevant after about 2 years. Therefore, €uro’s statement is not entirely correct, as there is indeed moisture present.

A passive house must not have a heating system; therefore, a mechanical ventilation system with heat recovery is a must-have. And despite all the "paper- or formula-based" calculations – if no one is living in the passive house during the day, those smart calculations are pointless; the building will be cold.

Regards, Bauexperte

Bauexperte, on the go

Bauexperte schrieb:
If no one lives in the penthouse during the day, all the clever calculations are pointless; the place is cold.

Unless enough cats live in the place...

A controlled residential ventilation system with heat recovery is definitely beneficial. We have had many clients whose homes were contaminated with mold spores; these were new builds where the owners decided against installing a controlled residential ventilation system. Mold is not always visible.
New builds are simply too airtight.