ᐅ Mechanical ventilation with heat recovery and still keeping windows open at night
Created on: 30 Aug 2016 14:23
K
Kaspatoo
Hi,
I would like to have a mechanical ventilation with heat recovery system in our newly built house, but we always sleep with the window open at night (mainly because of the cool, fresh-feeling air; warm air doesn’t feel fresh to me).
Here in the forum, I’ve read several times that many people just do this “without any issues.”
I’ve also often read that this could interfere with the mechanical ventilation system (it might "malfunction"). It was mentioned that this leads to increased wear and tear, but I couldn’t clearly identify exactly how and on which components this higher wear would occur. Apparently, this only happens if the system uses some kind of dynamic pressure control and doesn’t operate with a constant static pressure.
I have also read that this not only cools down the bedroom with the open window but, in the worst case, could cool the entire house because the ventilation system causes a temperature equalization. So either the heating has to compensate or the other rooms get colder.
For me as a layperson and reader, this means:
- If you have a mechanical ventilation system, make sure it does not have dynamic pressure control to avoid the “malfunction” problem.
- When planning the ventilation, ensure that at least the attic and the ground floor have separate circuits for the mechanical ventilation and are not connected “in series.”
Regarding the latter: As far as I understood correctly from a planner, the pipe layout would look like this: assuming you have four rooms in the attic (bathroom, 3 bedrooms), two rooms would get supply air ducts, and two rooms would get exhaust air ducts (one of those definitely the bathroom). The airflow then passes under the door.
1) If I open the window in an exhaust room, I would expect the following:
- At most, only my room cools significantly due to colder outside air coming in through the open window.
- It might be that little happens (almost no fresh air in the room), except that the outside air flows quite directly into the exhaust.
- Other rooms lose their air exhaust; the air might stagnate there, causing the air pressure to rise and the pressure increase to reach the supply air fan. This results in more resistance and could lead to higher wear (it’s like a freight train with locomotives at front and rear: if there’s no locomotive pulling at the front, the one at the back has it harder, although it won’t supply more power than set). In the extreme case, this would be like holding the supply air fan in place, which I believe is not good for the component in the long run.
- The question is: how serious is this or am I overthinking?
2) If I open the window in a supply air room, I would expect:
- In the worst case, the supply air flows directly outside, and I get nothing from the open window.
- The “pushing” locomotive has more load because the “pulling” locomotive is absent.
If the answer is: yes, opening windows is a bad idea with mechanical ventilation with heat recovery, then my follow-up question is: how do I prevent mold if I can’t regularly manage to open windows?
In summary, it seems to me there are only four possible options:
- Spend a lot of money on individual controls.
- Forget mechanical ventilation with heat recovery, ventilate manually and, if you ventilate too rarely, just skip the insulation and build a house like in the 1970s.
- Install mechanical ventilation with heat recovery and live without opening windows.
- Install mechanical ventilation with heat recovery, ventilate anyway, and accept the consequences (energy loss, system wear, disturbed indoor climate).
What do you think?
Which of my statements are correct, which are not?
Thanks a lot for your answers.
I would like to have a mechanical ventilation with heat recovery system in our newly built house, but we always sleep with the window open at night (mainly because of the cool, fresh-feeling air; warm air doesn’t feel fresh to me).
Here in the forum, I’ve read several times that many people just do this “without any issues.”
I’ve also often read that this could interfere with the mechanical ventilation system (it might "malfunction"). It was mentioned that this leads to increased wear and tear, but I couldn’t clearly identify exactly how and on which components this higher wear would occur. Apparently, this only happens if the system uses some kind of dynamic pressure control and doesn’t operate with a constant static pressure.
I have also read that this not only cools down the bedroom with the open window but, in the worst case, could cool the entire house because the ventilation system causes a temperature equalization. So either the heating has to compensate or the other rooms get colder.
For me as a layperson and reader, this means:
- If you have a mechanical ventilation system, make sure it does not have dynamic pressure control to avoid the “malfunction” problem.
- When planning the ventilation, ensure that at least the attic and the ground floor have separate circuits for the mechanical ventilation and are not connected “in series.”
Regarding the latter: As far as I understood correctly from a planner, the pipe layout would look like this: assuming you have four rooms in the attic (bathroom, 3 bedrooms), two rooms would get supply air ducts, and two rooms would get exhaust air ducts (one of those definitely the bathroom). The airflow then passes under the door.
1) If I open the window in an exhaust room, I would expect the following:
- At most, only my room cools significantly due to colder outside air coming in through the open window.
- It might be that little happens (almost no fresh air in the room), except that the outside air flows quite directly into the exhaust.
- Other rooms lose their air exhaust; the air might stagnate there, causing the air pressure to rise and the pressure increase to reach the supply air fan. This results in more resistance and could lead to higher wear (it’s like a freight train with locomotives at front and rear: if there’s no locomotive pulling at the front, the one at the back has it harder, although it won’t supply more power than set). In the extreme case, this would be like holding the supply air fan in place, which I believe is not good for the component in the long run.
- The question is: how serious is this or am I overthinking?
2) If I open the window in a supply air room, I would expect:
- In the worst case, the supply air flows directly outside, and I get nothing from the open window.
- The “pushing” locomotive has more load because the “pulling” locomotive is absent.
If the answer is: yes, opening windows is a bad idea with mechanical ventilation with heat recovery, then my follow-up question is: how do I prevent mold if I can’t regularly manage to open windows?
In summary, it seems to me there are only four possible options:
- Spend a lot of money on individual controls.
- Forget mechanical ventilation with heat recovery, ventilate manually and, if you ventilate too rarely, just skip the insulation and build a house like in the 1970s.
- Install mechanical ventilation with heat recovery and live without opening windows.
- Install mechanical ventilation with heat recovery, ventilate anyway, and accept the consequences (energy loss, system wear, disturbed indoor climate).
What do you think?
Which of my statements are correct, which are not?
Thanks a lot for your answers.
S
Sebastian7931 Aug 2016 05:47Normally sits inside the device, but there is also one for each outlet.
Just google the term, it is well explained by bosy.
It ensures that the volume flow remains constant, no matter what changes are made (valve opened, window open). This eliminates the need for complex calibration...
Just google the term, it is well explained by bosy.
It ensures that the volume flow remains constant, no matter what changes are made (valve opened, window open). This eliminates the need for complex calibration...
B
Bieber081531 Aug 2016 07:20Constant volume flow control according to Aldes (there is a PDF on aldes.de, and bosy cites Aldes as a source in his section). Components that use a membrane to maintain a constant volume flow over a relatively wide differential pressure range. After reading this, I still see no reason not to open a window.
Mechanically operated volume flow regulators are probably rare in private residential construction, right? But even there...
Mechanically operated volume flow regulators are probably rare in private residential construction, right? But even there...
S
Sebastian7931 Aug 2016 07:27Well, you just have to read a bit more. These are all devices that can basically be retrofitted – so it doesn’t really matter, or (to put it exaggeratedly) it depends on the lifespan of the additional units, because they regulate.
However, there are controlled residential ventilation systems that can adjust the air volume flow by regulating the speed of the fan motors – and there you have a constant variation in the fan speed. An open window naturally disrupts the volume flow....
However, there are controlled residential ventilation systems that can adjust the air volume flow by regulating the speed of the fan motors – and there you have a constant variation in the fan speed. An open window naturally disrupts the volume flow....
Hi,
I didn’t express myself clearly.
I mean, if I want to be able to open windows (at night, in the bedroom, every night on warm days, maybe only an hour before bedtime on cold days), and doing that together with a controlled ventilation system doesn’t make sense or would be totally pointless, then for me the conclusion would be that a controlled ventilation system doesn’t make sense in my case.
However, the house is still well insulated and airtight. Therefore, I have to compensate for this by manually ventilating. But I assume I won’t manage to do that regularly three times a day.
My counter-question was aimed at this scenario: how do I prevent mold growth when ventilating manually?
The only things that come to mind are decentralized ventilation and something like trickle vents in the window frame.
And then there are the counterarguments that all the insulation would be pointless anyway.
A bleak dilemma for fans of cool fresh air while sleeping (cool air feels fresher = better comfort).
But you yourselves said you also sometimes open the window.
What I still don’t quite understand:
- There are systems that can dynamically adjust their fan speed — is that true, or do they simply apply a fixed wattage to the fan, and if it has a harder or easier time, it runs faster or slower?
- Conversely, does that mean there are also systems without this capability?
-> Can those also cause problems if the window is opened frequently?
- Now you mentioned the “constant pressure regulator,” which according to the above definition sounds complicated, involving membranes, etc.
-> But if I have a device without dynamic control, isn’t that the same as a constant pressure regulator?
-> Why the elaborate technology with membranes and so forth if you could simply omit dynamic control?
In other words, if I were to choose a system, what should I be paying attention to?
I didn’t express myself clearly.
I mean, if I want to be able to open windows (at night, in the bedroom, every night on warm days, maybe only an hour before bedtime on cold days), and doing that together with a controlled ventilation system doesn’t make sense or would be totally pointless, then for me the conclusion would be that a controlled ventilation system doesn’t make sense in my case.
However, the house is still well insulated and airtight. Therefore, I have to compensate for this by manually ventilating. But I assume I won’t manage to do that regularly three times a day.
My counter-question was aimed at this scenario: how do I prevent mold growth when ventilating manually?
The only things that come to mind are decentralized ventilation and something like trickle vents in the window frame.
And then there are the counterarguments that all the insulation would be pointless anyway.
A bleak dilemma for fans of cool fresh air while sleeping (cool air feels fresher = better comfort).
But you yourselves said you also sometimes open the window.
What I still don’t quite understand:
- There are systems that can dynamically adjust their fan speed — is that true, or do they simply apply a fixed wattage to the fan, and if it has a harder or easier time, it runs faster or slower?
- Conversely, does that mean there are also systems without this capability?
-> Can those also cause problems if the window is opened frequently?
- Now you mentioned the “constant pressure regulator,” which according to the above definition sounds complicated, involving membranes, etc.
-> But if I have a device without dynamic control, isn’t that the same as a constant pressure regulator?
-> Why the elaborate technology with membranes and so forth if you could simply omit dynamic control?
In other words, if I were to choose a system, what should I be paying attention to?
S
Sebastian7931 Aug 2016 10:17You should read texts fully first; then all questions become unnecessary...
Forget membranes, etc. – devices with a constant volume flow control manage that internally through speed detection and who knows what else. That is also advertised...
Without this technology, as I already mentioned, there are no problems because the ventilation is simple and just runs continuously.
Forget membranes, etc. – devices with a constant volume flow control manage that internally through speed detection and who knows what else. That is also advertised...
Without this technology, as I already mentioned, there are no problems because the ventilation is simple and just runs continuously.
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