We will be installing a central ventilation system from Zehnder. I am considering the "Zehnder ComfoAir Qxxx" model since I will also be implementing a KNX system.
The unit is available in three versions:
- up to 350 m³/h (210 cfm)
- up to 450 m³/h (265 cfm)
- up to 600 m³/h (355 cfm)
The house will have around 170 m² (1,830 sq ft) of living space, and there are currently 3 occupants (another child is possible).
Which of these three units would you choose? Of course, it shouldn’t always run at full capacity, but it also shouldn’t be oversized.
The unit is available in three versions:
- up to 350 m³/h (210 cfm)
- up to 450 m³/h (265 cfm)
- up to 600 m³/h (355 cfm)
The house will have around 170 m² (1,830 sq ft) of living space, and there are currently 3 occupants (another child is possible).
Which of these three units would you choose? Of course, it shouldn’t always run at full capacity, but it also shouldn’t be oversized.
Thank you for your responses. I can’t say what air exchange rate should be aimed for. My priority is fresh, good air without having to open the windows and without introducing too much moisture into the house.
If possible, I would also prefer not to hear the system running, so it shouldn’t have to operate at full power.
But okay, the statement is that 350 should be sufficient. The 600 is probably oversized. I will check the price difference between 350 and 450 and then make a decision.
If possible, I would also prefer not to hear the system running, so it shouldn’t have to operate at full power.
But okay, the statement is that 350 should be sufficient. The 600 is probably oversized. I will check the price difference between 350 and 450 and then make a decision.
We have the Comfoair 350 for a 125 m² (1,345 sq ft) house. The ventilation usually runs at setting 2 out of 3, which corresponds to about 40-50% of its capacity. For a 170 m² (1,830 sq ft) house, the system might be a bit undersized. It’s better to operate the unit at a lower level because running it at full capacity consumes significantly more electricity! The larger models apparently also have a bigger impeller.
Basically, the size doesn’t matter that much, since an undersized system isn’t a serious issue. The air exchange still takes place, just at a lower rate. On the other hand, the bigger unit doesn’t cost much more, so it’s better to choose a slightly larger one right away.
Basically, the size doesn’t matter that much, since an undersized system isn’t a serious issue. The air exchange still takes place, just at a lower rate. On the other hand, the bigger unit doesn’t cost much more, so it’s better to choose a slightly larger one right away.
Hi,
A few hundred would still be worth it for me; currently, there is about a €650 (about $700) difference.
€2070 (about $2200) for the 350 model
€2720 (about $2900) for the 450 model.
That’s a hefty 30% surcharge. And that’s just for the larger one to produce 1 dB less noise? Power consumption is almost identical as well.
If anyone finds a better price, please send me a PM, since I need to place an order soon...
Best regards,
Andreas
Alex85 schrieb:
The additional cost is about 20-25%, or a few hundred euros, compared to the Q450 model.
A few hundred would still be worth it for me; currently, there is about a €650 (about $700) difference.
€2070 (about $2200) for the 350 model
€2720 (about $2900) for the 450 model.
That’s a hefty 30% surcharge. And that’s just for the larger one to produce 1 dB less noise? Power consumption is almost identical as well.
If anyone finds a better price, please send me a PM, since I need to place an order soon...
Best regards,
Andreas
I just looked up our apartment ventilation calculation (it was provided to us).
All values are approximate and only for reference:
Parameters: normal location, residential unit 0-15m (0-49 feet) above ground level, high thermal insulation (new building), wind-exposed area near the North Sea (30-40km/h or 19-25 mph wind speeds).
Volume to be ventilated: 315m³ (126m² (1356 ft²) floor area x 2.5)
Airflow rate for moisture protection: 45m³/h (27 cubic feet per minute) (unfortunately, it does not state how this value was calculated).
From this, the sizing of the ventilation system is determined:
Moisture protection ventilation (when absent): 55m³/h (32 cfm)
Nominal ventilation (level 2/3): 185m³/h (109 cfm)
Intensive ventilation: 240m³/h (141 cfm)
From this, it can be seen that roughly 0.6 times the building volume per hour is needed as nominal capacity (at least for a house of this size). For a 170m² (1830 ft²) house multiplied by 2.5 (425m² (4573 ft²)), this equals 270m³/h (159 cfm) required nominal capacity. This corresponds to level 6 of 8 on the ComfoAir system, with a power consumption of 105 watts, which is quite substantial. The ComfoAir 550, at 265m³/h (156 cfm), only consumes 69 watts, making a difference of 35 watts per hour. Over 8,760 hours per year, this adds up to roughly 300 kWh saved. At an electricity price of about 30 cents per kWh, that’s almost 90 euros saved annually.
And this is exactly where the advantage of larger systems lies: they simply run more efficiently at these airflow rates.
Oh, and if you want KfW funding with your ventilation system, it must be calibrated by someone (or you need a flow measuring device and a plan showing how much air should come from each opening). Otherwise, more air will come out of the ducts closest to the ventilation unit than from those furthest away. If not properly balanced, the KfW advisor will reject the application at the end of the build.
Hope this helps a bit.
All values are approximate and only for reference:
Parameters: normal location, residential unit 0-15m (0-49 feet) above ground level, high thermal insulation (new building), wind-exposed area near the North Sea (30-40km/h or 19-25 mph wind speeds).
Volume to be ventilated: 315m³ (126m² (1356 ft²) floor area x 2.5)
Airflow rate for moisture protection: 45m³/h (27 cubic feet per minute) (unfortunately, it does not state how this value was calculated).
From this, the sizing of the ventilation system is determined:
Moisture protection ventilation (when absent): 55m³/h (32 cfm)
Nominal ventilation (level 2/3): 185m³/h (109 cfm)
Intensive ventilation: 240m³/h (141 cfm)
From this, it can be seen that roughly 0.6 times the building volume per hour is needed as nominal capacity (at least for a house of this size). For a 170m² (1830 ft²) house multiplied by 2.5 (425m² (4573 ft²)), this equals 270m³/h (159 cfm) required nominal capacity. This corresponds to level 6 of 8 on the ComfoAir system, with a power consumption of 105 watts, which is quite substantial. The ComfoAir 550, at 265m³/h (156 cfm), only consumes 69 watts, making a difference of 35 watts per hour. Over 8,760 hours per year, this adds up to roughly 300 kWh saved. At an electricity price of about 30 cents per kWh, that’s almost 90 euros saved annually.
And this is exactly where the advantage of larger systems lies: they simply run more efficiently at these airflow rates.
Oh, and if you want KfW funding with your ventilation system, it must be calibrated by someone (or you need a flow measuring device and a plan showing how much air should come from each opening). Otherwise, more air will come out of the ducts closest to the ventilation unit than from those furthest away. If not properly balanced, the KfW advisor will reject the application at the end of the build.
Hope this helps a bit.
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