ᐅ Central Vacuum Exhaust: Is an Open Pipe or a Sealed Wall Box More Appropriate?
Created on: 14 Dec 2025 15:43
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Ganneff
Hello,
Our construction plan includes a central vacuum system (which is already planned in detail). However, there is one aspect I haven’t been able to resolve satisfactorily, and maybe someone here has good input? (By the way, this is not about the pros and cons of a central vacuum system. There are different opinions on that, but that’s another topic.)
Specifically, the exhaust duct uses a 100mm (4 inch) pipe that leads outside. Typically, there is just a bit of plastic on the outside with an insect screen underneath, and nothing more.
I wonder if it wouldn’t be much better to install a wall box that seals tightly and only allows air to pass when the vacuum is running. Otherwise, the pipe represents quite a large thermal bridge in an otherwise well-sealed house. There are various options available, and the exact model is not so important. Searching for “wall box blower door” online reveals several products designed to achieve this. They are usually intended for range hoods, but that does not make much difference in this case—range hoods also have a large hole in the wall when venting.
I’m not interested in ideas like “directing it into the ventilation system so the heat exchanger can handle it,” because the vacuum would push too much air in and disrupt the ventilation (and then I would be bringing that exhaust air back into the house, which is exactly what I want to avoid).
Our construction plan includes a central vacuum system (which is already planned in detail). However, there is one aspect I haven’t been able to resolve satisfactorily, and maybe someone here has good input? (By the way, this is not about the pros and cons of a central vacuum system. There are different opinions on that, but that’s another topic.)
Specifically, the exhaust duct uses a 100mm (4 inch) pipe that leads outside. Typically, there is just a bit of plastic on the outside with an insect screen underneath, and nothing more.
I wonder if it wouldn’t be much better to install a wall box that seals tightly and only allows air to pass when the vacuum is running. Otherwise, the pipe represents quite a large thermal bridge in an otherwise well-sealed house. There are various options available, and the exact model is not so important. Searching for “wall box blower door” online reveals several products designed to achieve this. They are usually intended for range hoods, but that does not make much difference in this case—range hoods also have a large hole in the wall when venting.
I’m not interested in ideas like “directing it into the ventilation system so the heat exchanger can handle it,” because the vacuum would push too much air in and disrupt the ventilation (and then I would be bringing that exhaust air back into the house, which is exactly what I want to avoid).
nordanney schrieb:
First, off topic: Central vacuum systems are outdated nowadays due to the availability of very good cordless vacuum cleaners, because a) they are far too expensive for the performance and b) they are still too inconvenient to use.Even with a very good cordless vacuum cleaner, the exhaust air is blown right back into the room. And I know the performance—it surpasses all the others I have seen so far.nordanney schrieb:
Regarding the question: Of course, a simple opening in a newly built house is basically a disaster. That's not acceptable. You first build an airtight house and then install an opening through which a lot of cold outside air can flow in. A wall box is a must-have.
[... Text for an electrical box ...]
It also has the advantage that particles that might settle do not obstruct the opening as much as they possibly would with a mechanical solution.Okay, that confirms my thoughts. There are a few options, ranging from somewhat reasonable in price to “Are you serious?” What matters to me is that the unit passes the blower door test. But definitely a proper box is needed.For the sake of completeness: The system was redesigned, and the main unit will be placed in the adjacent room next to the garage. From the house, the pipe will be routed through the foundation and floor. It will run alongside the pipes I’m already installing for electrical and network cables. This way, the exhaust outlet will be located in the garage, where the issue of airtightness is not a concern, and the few extra meters of length don’t matter.
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wiltshire21 Dec 2025 15:26The crucial point is that the duct must be completely airtight when turned off. Without any draft, the air inside the duct acts as an effective insulator, and heat loss from the shaft can be neglected. This is usually achieved cost-effectively with spring-loaded dampers or magnetic systems combined with appropriate sealing materials (silicone, soft rubber, etc.). Simply having open slats facing outward would not be sufficient for my taste.
A central vacuum system offers advantages for sensitive allergy sufferers compared to systems that release exhaust air into the room, directly improving quality of life. Naturally, in terms of convenient home automation, the much more affordable vacuum-mopping robots on the market have become far more popular. This explains why central vacuum systems still have their place but are requested less frequently.
A central vacuum system offers advantages for sensitive allergy sufferers compared to systems that release exhaust air into the room, directly improving quality of life. Naturally, in terms of convenient home automation, the much more affordable vacuum-mopping robots on the market have become far more popular. This explains why central vacuum systems still have their place but are requested less frequently.
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