ᐅ Mechanical Ventilation with Heat Recovery – You Can Hear Every Word from Another Room – Is This Normal?

Hello everyone,
We had the final inspection of our house two weeks ago. Now we have noticed that through the central ventilation system in the guest bathroom and utility room, every word spoken in the dining/kitchen/living area can be heard very clearly, as if you were sitting right next to each other. With the bathroom door open, the sound naturally carries up to the children’s bedrooms upstairs. On the upper floor, the sound transmission through the controlled mechanical ventilation system is significantly less.
Can I still report this as a defect after the final inspection?
Thank you very much and best regards!

It is normal for sound to travel through the air. Ventilation ducts can hardly filter out a "sound track."

However, the ventilation system is not intended to serve as an intercom.

Dodo86 schrieb:
Can I still report this as a defect after the final inspection?

If you are unsure whether something is a defect, the general rule should be: it’s better to report it once too often and not delay.

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Dodo86 schrieb:
Can I still claim this as a defect after the final inspection?

Yes, definitely. I would advise not to mention too many details (such as mechanical ventilation with heat recovery...). The defect is primarily the inadequate (ha ha) sound insulation. You shouldn’t write too much about the causes, as that can only backfire. After the final inspection, it’s naturally more difficult (reversal of the burden of proof). Therefore, it’s advisable to consult an expert. There’s no urgency anymore, so a few days delay won’t matter.

Pure curiosity: Have you tried blocking the mechanical ventilation system (for example, stuffing a cloth into the duct) to narrow down the cause? During operation, the sound wave might even travel against the airflow. And “around the corner” (the ductwork is unlikely to run in a straight line) and then through the central unit (I’m assuming a typical centralized mechanical ventilation system with heat recovery). ... You can tell I don’t believe the mechanical ventilation is the cause. What is the wall construction like?

Is there a sound damper installed?

At a reputable company, someone would come by to take a look. They would quickly realize if something has gone wrong. At first, an expert assessor or surveyor is not necessary. If you always start by threatening legal action, they will be unwilling to help. It might just be a small issue, and the problem could be resolved within 1–2 hours.

Normally, you don’t hear sounds from room to room because, with a central ventilation system, the ducts run individually as risers to the utility room, where they are connected using T-pieces.

Thank you for the answers,
Yes, I spoke with the contractor today. They will come on Thursday to take a look.
However, they also initially thought the noise would definitely come through the doors. But it is heard that it comes from the central ventilation system. It sounds like someone is speaking into a duct (which apparently is the case). The doors block the sound well. The wall construction consists of Ytong blocks on the ground floor and drywall on the upper floor, with all walls upstairs reinforced with OSB panels.
Oh, and the noise of the mechanical ventilation system, which originates in the utility room, is also very loud through the supply air vents. The mechanical ventilation system (from Nibe) is set to normal. Do you also hear this noise through the ceiling supply air outlets?