ᐅ Exhaust Air vs. Recirculation in a Mechanical Ventilation with Heat Recovery System
Created on: 4 Jan 2017 22:12
M
Momad
Hello,
we are building a KfW 70 semi-detached house with a controlled ventilation system, and now I am facing the decision between exhaust air or recirculating air in the kitchen. Unfortunately, I can’t find clear answers on this in the forum or online in general.
My general contractor said it’s no problem and that they can install an exhaust air system if desired.
In five different kitchen showrooms, I received five different answers and recommendations (definitely no exhaust air, exhaust air is prohibited, recirculating air is fine, exhaust air is better, etc.).
How have you solved this in your homes, and which factors are crucial for making this decision?
Thank you!
we are building a KfW 70 semi-detached house with a controlled ventilation system, and now I am facing the decision between exhaust air or recirculating air in the kitchen. Unfortunately, I can’t find clear answers on this in the forum or online in general.
My general contractor said it’s no problem and that they can install an exhaust air system if desired.
In five different kitchen showrooms, I received five different answers and recommendations (definitely no exhaust air, exhaust air is prohibited, recirculating air is fine, exhaust air is better, etc.).
How have you solved this in your homes, and which factors are crucial for making this decision?
Thank you!
Hello Teyla, we purchased the duct box directly from the kitchen showroom. I wouldn't do that today, as you can get it cheaper elsewhere. I had the builder drill a hole for it. This isn’t easy in aerated concrete since the core drill can’t be properly secured. After the exterior plaster was applied, I installed the box. Ideally, I think it would be best to install the box between the base coat and finish coat of plaster. This should be discussed with the plasterer. I had to scrape off some plaster so that the mounting collar of the extractor hood would be flush with the wall. Now the stainless steel cover only protrudes by the 2mm (0.08 inches) thickness it has itself. Otherwise, the flap works very well. Occasionally, wind suction lifts it, but very rarely, and it’s quite windy here. Perhaps the wind rarely comes from the direction where the wind suction would be a problem. Also, the extractor hood provides enough pressure to press it closed even against the wind.
Bratac
Bratac
BratacDD schrieb:
Hello,
we also have a central controlled residential ventilation system and an exhaust hood, and for the distribution box we use the FLOWSTAR150 from Naber. It looks nice and works well. What has been your experience with the exhaust hood and the controlled residential ventilation system?
Does it not cause negative pressure in your case?
Wouldn’t you need to provide additional fresh air intake, for example by tilting a window?
Yes, a negative pressure is created, but I only tilt the window when I run the hood at maximum power. You can notice it when you open a window or door. I have not been able to detect any impairment of the ventilation system.
It should be mentioned that I installed the exhaust system myself, so I am responsible for any possible complications. If a general contractor (GC) were hired to install the exhaust and ventilation system, there would probably be a thousand reasons why it couldn’t be done, since the GC would be liable in case of any issues.
It should be mentioned that I installed the exhaust system myself, so I am responsible for any possible complications. If a general contractor (GC) were hired to install the exhaust and ventilation system, there would probably be a thousand reasons why it couldn’t be done, since the GC would be liable in case of any issues.
For us, this topic is still not resolved. A controlled residential ventilation system is planned.
Recirculation systems cost a significant amount of money if they are to work properly and generate ongoing expenses. There is simply nothing under €2000 (around $2200) that does not just push odors and grease back into the room. Especially not if it is not going to be a wall-mounted solution, but rather something to be hung over an island or similar setup—and then actually function properly (distance between pot and exhaust).
At the moment, we are somewhat going in circles regarding this issue.
Recirculation systems cost a significant amount of money if they are to work properly and generate ongoing expenses. There is simply nothing under €2000 (around $2200) that does not just push odors and grease back into the room. Especially not if it is not going to be a wall-mounted solution, but rather something to be hung over an island or similar setup—and then actually function properly (distance between pot and exhaust).
At the moment, we are somewhat going in circles regarding this issue.
Thank you @BratacDD!
@Knallkörper: How is it going with you regarding negative pressure and its interaction with the mechanical ventilation with heat recovery?
@Alex85: I feel the same right now, although I am leaning towards a reliable exhaust solution (Berbel wall box) at 95%. We currently have exhaust in our power kitchen, which works well, but I still have to wipe off grease and clean afterward. I can't imagine managing this properly with a standard recirculation system. And grease in my mechanical ventilation with heat recovery must definitely be avoided.
@Knallkörper: How is it going with you regarding negative pressure and its interaction with the mechanical ventilation with heat recovery?
@Alex85: I feel the same right now, although I am leaning towards a reliable exhaust solution (Berbel wall box) at 95%. We currently have exhaust in our power kitchen, which works well, but I still have to wipe off grease and clean afterward. I can't imagine managing this properly with a standard recirculation system. And grease in my mechanical ventilation with heat recovery must definitely be avoided.
K
Knallkörper6 Jan 2017 19:17Hello.
I am generally skeptical about ventilation systems. Our old house is not really airtight; it tends to have some drafts when it’s windy. However, the exhaust hood still moves significantly more air when a window is opened, and you can hear it. The air volume moved by the hood is roughly an order of magnitude higher than that of the mechanical ventilation with heat recovery system, and the pressure difference might be two orders of magnitude. This can only really work if the mechanical ventilation is set to full bypass mode—meaning all dampers open, supply air also flowing through the exhaust, and the fan off. Or alternatively: by slightly opening a window.
I am generally skeptical about ventilation systems. Our old house is not really airtight; it tends to have some drafts when it’s windy. However, the exhaust hood still moves significantly more air when a window is opened, and you can hear it. The air volume moved by the hood is roughly an order of magnitude higher than that of the mechanical ventilation with heat recovery system, and the pressure difference might be two orders of magnitude. This can only really work if the mechanical ventilation is set to full bypass mode—meaning all dampers open, supply air also flowing through the exhaust, and the fan off. Or alternatively: by slightly opening a window.
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