ᐅ Controlled Residential Ventilation System – Decision Guide

Created on: 22 Oct 2017 11:14
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baumhaus815
Hello everyone,

We have decided to build with GÜ, and construction is about to start soon. Now we need to choose a specific mechanical ventilation with heat recovery system.

The single-family house has three floors (basement, ground floor, upper floor), and the floor area of each level is about 80 sqm (860 sq ft). The mechanical ventilation system is planned only for the ground and upper floors, not for the basement.

We are currently choosing between two systems: the Zehnder Comfoair Q350 and the Wolf CWL-300. The Wolf system would be 1,700 euros cheaper overall (including ductwork, installation, etc.).

From what I understand, the Comfoair Q350 is the newer system, has lower noise levels, and a higher heat recovery efficiency. Additionally, it is dimensioned for 50 m3 (1,765 cu ft) more airflow than the CWL-300, which might mean it could run at a lower fan setting during normal operation, making it quieter and more economical.

Our considerations now are: Do the lower measured noise levels actually make a noticeable difference in everyday use (or only under laboratory conditions)? Regarding the system sizing: In theory, 300 m3 (10,595 cu ft) max capacity would be sufficient for us, but would 350 m3 (12,366 cu ft) be better in practice? Ultimately, the Comfoair Q350 is probably the better system, but we wonder if the additional 1,700 euro cost is worth it for our house.

Which mechanical ventilation with heat recovery system would you recommend as experts? As non-professionals, it’s quite difficult for us to make the right choice.

Thanks in advance!
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Aotearoa
22 Oct 2017 13:17
For the ground floor and upper floor, with a similar square meter area, we have the Zehnder 350 units, and we only hear the ventilation at the highest setting. The normal operation is the medium setting, and I don’t really hear any noise there, even when it’s quiet.
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Bieber0815
23 Oct 2017 11:26
Do the systems differ in the types of valves and piping used? What pipe diameters are planned? Which valve types and flow restrictors are included? How is the fresh air supplied from outside? Are there any differences in this regard?

How is the basement integrated into the ventilation concept? Is there a separate ventilation plan for the basement? Does air build up there that needs to be exhausted?
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munger71
23 Oct 2017 21:05
I would definitely include the basement in the ventilation plan. We did the same. We are using a Vallox MV-350E.
bon198023 Oct 2017 23:00
We have the CWL-300 installed in the basement, with a similar square meter area, but in our case, all basement rooms are ventilated.
We only hear the ventilation (the air noise) at level 4 (of 4), and when it’s very quiet, also at level 3. Our standard setting is level 2.
You can barely hear the unit itself at the top of the basement stairs even at the highest setting (of course, the door to the utility room needs to be closed).
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baumhaus815
24 Oct 2017 17:22
OK, thanks so far for the responses. We will ask about the cost of integrating the basement into the ventilation system as well. It probably won’t add much additional cost (I hope), since the ductwork would be significantly shorter than in the two living floors above.

Now I thought of something else: Our living room is about 30m² (320ft²) and currently only one air inlet is planned there. To achieve the required m³ airflow volume, I think a higher pressure would be needed with only one inlet compared to two inlets. Possible downsides could be stronger drafts and increased noise levels.

What do the experts think? Wouldn’t it be better to plan two air inlets for a 30m² (320ft²) room?
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munger71
24 Oct 2017 17:33
We have planned approximately 20m³ (706 cubic feet) of air volume per 20m² (215 square feet) of living space.
For example, in a 35m² (377 square feet) room, two 100mm (4 inch) round supply air diffusers, each providing 20m³ (706 cubic feet) of air, are used.