ᐅ Decentralized ventilation units for larger rooms (older buildings)
Created on: 1 Oct 2025 17:46
R
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
R
RealUnreal2 Oct 2025 20:19Gerddieter schrieb:
Have you ever seen a decentralized rotary heat exchanger like that? The units are huge—I wouldn’t want to spoil the look of my apartment with one. As I already mentioned: I have a Bavarian-style ventilator in the laundry room.
By the way, I installed it myself.
I know exactly what it looks like.
R
RealUnreal2 Oct 2025 20:28Gerddieter schrieb:
For me, classic decentralized demand-controlled ventilators with heat recovery would be ideal; you basically only see the cover. Choose a model with a flat cover and a maximum size of 10cm by 10cm (4 inches by 4 inches).The problem there is the noise level. The constant switching of the fans makes it noticeably louder, from everything I have read.N
nordanney2 Oct 2025 20:40RealUnreal schrieb:
The problem is the noise level.
Constantly switching the fans makes it noticeably louder, according to everything I’ve read. Louder than what exactly? At which setting? Yes, they are louder. But not loud.
On the other hand, they are 4-6 times smaller and 3-4 times more affordable.
R
RealUnreal3 Oct 2025 09:14nordanney schrieb:
Significantly louder than what? At which setting? Yes, they are louder. But not loud.Significantly louder than Meltem and Bayernlüfter.
And with much less power.
N
nordanney3 Oct 2025 09:39RealUnreal schrieb:
Clearly louder than Meltem and Bayern fans.
And with much less power.I don’t understand. Which fans do you have, and which fans are you comparing what with?R
RealUnreal3 Oct 2025 10:24Let's take the "Meltem M-heat recovery II" as an example. It has a capacity of 10-100 cubic meters per hour. At 50 cubic meters per hour, it produces an indoor noise level of 33.9 dB.
Are there any balanced fans that can compete with this?
Are there any balanced fans that can compete with this?