ᐅ Decentralized ventilation units for larger rooms (older buildings)
Created on: 1 Oct 2025 17:46
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RealUnreal
Hello everyone,
I have an older building, built in 1976.
Next year, I plan to install triple-glazed windows in several rooms.
The exterior walls have U-values mostly around 0.90, with some individual exterior walls as high as 1.4.
In one room (laundry room), I have been using a Bavarian-style ventilator (ventilation with heat recovery) for about two years, and since then, I have had no moisture problems, even though the window is always closed and sometimes a clothes dryer is running and damp laundry is being dried.
The rooms where the windows will be replaced are quite large.
One room is 66 m² (room volume 178.2 m³ (6291 ft³)).
The other room consists of a main area (living room) with 48 m² (room volume 130.39 m³ (4603 ft³)) and an adjoining kitchen (separated only by a glass door) with about 15 m² (room volume 40.96 m³ (1445 ft³)).
I would like a decentralized ventilation system with heat recovery for both rooms to avoid condensation issues with the new windows and to remove any excess humidity.
This would only replace manual ventilation since I do not want to have to ventilate constantly.
Only my wife and I live in the apartment (2 persons).
I do not want a alternating system but rather a unit with heat recovery and separate fans for supply and exhaust air.
I want to install the units myself (I also installed the Bavarian ventilator).
So, the installation should not be more complicated than the Bavarian ventilator.
The problem is that the house is built on a slope.
I can only exhaust to the front side (valley side), which has fairly large window fronts.
No more than one ventilation unit fits per room, and only if I reduce the size of one window.
In the meantime, I spoke with the company Meltem, and they said that a "heat recovery-II" unit would be sufficient for the living room.
They would recommend an airflow rate of 50 m³/h (about 30 CFM).
For the other room, they actually recommend two units with the same settings.
With the Bavarian ventilator, you generally estimate an air exchange rate of about 0.2 times per hour, so in 5 hours a complete exchange of air occurs.
I can easily achieve this or do it faster with the Meltem device.
The older "heat recovery" model (without II) is about 400.00 Euros cheaper, but the newer device is clearly recommended.
I would go for a version with a humidity sensor and controls.
What do you think?
Two units in one room is a bit difficult.
Maybe additionally window frame ventilators?
Best regards,
Unreal
I have an older building, built in 1976.
Next year, I plan to install triple-glazed windows in several rooms.
The exterior walls have U-values mostly around 0.90, with some individual exterior walls as high as 1.4.
In one room (laundry room), I have been using a Bavarian-style ventilator (ventilation with heat recovery) for about two years, and since then, I have had no moisture problems, even though the window is always closed and sometimes a clothes dryer is running and damp laundry is being dried.
The rooms where the windows will be replaced are quite large.
One room is 66 m² (room volume 178.2 m³ (6291 ft³)).
The other room consists of a main area (living room) with 48 m² (room volume 130.39 m³ (4603 ft³)) and an adjoining kitchen (separated only by a glass door) with about 15 m² (room volume 40.96 m³ (1445 ft³)).
I would like a decentralized ventilation system with heat recovery for both rooms to avoid condensation issues with the new windows and to remove any excess humidity.
This would only replace manual ventilation since I do not want to have to ventilate constantly.
Only my wife and I live in the apartment (2 persons).
I do not want a alternating system but rather a unit with heat recovery and separate fans for supply and exhaust air.
I want to install the units myself (I also installed the Bavarian ventilator).
So, the installation should not be more complicated than the Bavarian ventilator.
The problem is that the house is built on a slope.
I can only exhaust to the front side (valley side), which has fairly large window fronts.
No more than one ventilation unit fits per room, and only if I reduce the size of one window.
In the meantime, I spoke with the company Meltem, and they said that a "heat recovery-II" unit would be sufficient for the living room.
They would recommend an airflow rate of 50 m³/h (about 30 CFM).
For the other room, they actually recommend two units with the same settings.
With the Bavarian ventilator, you generally estimate an air exchange rate of about 0.2 times per hour, so in 5 hours a complete exchange of air occurs.
I can easily achieve this or do it faster with the Meltem device.
The older "heat recovery" model (without II) is about 400.00 Euros cheaper, but the newer device is clearly recommended.
I would go for a version with a humidity sensor and controls.
What do you think?
Two units in one room is a bit difficult.
Maybe additionally window frame ventilators?
Best regards,
Unreal
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nordanney6 Oct 2025 09:15RealUnreal schrieb:
Is it possible to install such a device yourself if you are able to install a decentralized unit?Sure, you just need to have the volume flow rates calculated. Several manufacturers also offer free system design services, including a list of required components. RealUnreal schrieb:
I don’t understand that 🙄You can’t simply reply with “Yes” or similar. There is a minimum word and character count required.R
RealUnreal6 Oct 2025 09:48nordanney schrieb:
Sure, you just need to have the volume flow rates calculated. Several manufacturers will also design the system for you free of charge, including the necessary components.Very interesting.
Thank you!
Would you prefer a specific manufacturer for that?
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RealUnreal6 Oct 2025 19:55One more question: Do you think about 20 meters (65 feet) of pipe length from the main unit to the room will be an issue?
I’ve contacted a plumber who will check it out at the end of the month.
Maybe I can save quite a bit by doing some of the work myself, like making wall openings and laying the pipes...
I’ve contacted a plumber who will check it out at the end of the month.
Maybe I can save quite a bit by doing some of the work myself, like making wall openings and laying the pipes...
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nordanney6 Oct 2025 22:50RealUnreal schrieb:
Would you prefer any specific manufacturer there? No.
RealUnreal schrieb:
Do you think about 20 meters (65 feet) of pipe length from the main unit to the room would be a problem? No. That should not be an issue either (choose suitable equipment and take it into account during the calculation).
Why not supply all rooms directly?
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RealUnreal7 Oct 2025 06:46nordanney schrieb:
Why not supply all rooms directly?I plan to replace about 60% of the windows next year.
In the other rooms with the (for now) old windows, it is not necessary yet.
The important thing is that it can be easily expanded.
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RealUnreal7 Oct 2025 16:36One more question: Do you know the typical diameter of the (flexible?) pipes leading to the individual rooms in a central system?