Interpretation of a central ventilation system

Hello everyone,

for our new construction project at KfW55 level, we are planning the installation of a central ventilation system with heat recovery (yes, we discussed it at length and decided on it). Now I have received the first planning from Zehnder, see attachment.

Some points have not been recorded correctly, e.g. the height on the upper floor, as we are planning an "open ceiling" here. The calculation is based on a ceiling height of 2.50m, which is clearly too low. The other height information is also inconsistent; once the top edge of the finished floor level (ground floor) and once the OKRB (basement) were used. I have already complained about this.
Aside from that, I keep reading that the system is rather somewhat oversized, in order to have reserves on the one hand and to be able to operate at partial load on the other. Zehnder proposed Q350TR to us.
What also makes me suspicious is the low number of supply air vents – or am I mistaken? For example, no vents are present in the hallway/wardrobe area. Also, in the bedrooms and children's rooms, I would have thought of 2 vents (?).






It is important to us that as little noise and/or drafts as possible are perceived and that we do not have to regret a wrong decision afterwards that initially appeared to be a saving measure. We are not committed to a manufacturer; Zehnder, because I have only read good things about it so far.

Thank you for reviewing this!

Best regards,
Jentopa

That fits as planned. Corridors are overflow areas and do not require valves. I would, however, plan an exhaust valve in the [HAR]. In the bedrooms, usually only one supply air valve is sufficient if no special requirements are imposed.

Thank you very much
Do you mean an additional exhaust vent in the HAR? One is already planned.
Does the building volume not play a role in the design or calculation?
What is your opinion on the ventilation unit, is it sufficient or would a larger one (Q450) be better?
Just a quick note on our special requirements in case that’s what you mean: as quiet as possible, especially in the bedrooms. Hence my idea of the 2 supply air vents with half the airflow each - if that makes sense.
Sorry for all the questions.

Do you mean an additional exhaust vent in the HAR? One is already planned.

I must have overlooked that.

Does the building volume not play a role in the design or calculation?

Of course it does. But everything is within the safe range for you.

What is your opinion on the ventilation unit, is it sufficient or would a larger model (Q450) be better?

The 350 is sufficient. But of course, you can take the 450 if you prefer.

Just briefly regarding our special requirements if you mean that: as quiet as possible, especially in the bedrooms. Hence my idea with the 2 supply air vents each with half the airflow – if that makes sense.

You can simply have a larger vent installed, then the exit noise will be even quieter. For example, I only hear my system at full load and I have a very light sleep.

Thank you again for your feedback. I had a phone call with the planner today to go through everything again; until I understand it. A preheating coil was also offered to us optionally. I need to follow up on this as well.

Depends on where you live, but usually in [D] not necessary.