ᐅ Insulated drywall enclosure for controlled residential ventilation unit in the attic
Created on: 25 Mar 2020 19:01
A
annab377
Hello everyone,
I have two questions regarding the following proposal from our architect:
We are planning a two-story house with a pitched roof and a basement. He recommends installing the central mechanical ventilation system with heat recovery in the attic (this avoids breaking through the basement wall and having a "little tower" in the garden). However, the attic is intended to be outside the thermal envelope (insulation will be added on top of the concrete ceiling of the first floor). Since the attic can get quite cold without insulation, and according to him the ventilation system does not work well in rooms colder than 10°C (50°F), we are advised to build an insulated small room for the ventilation system on one gable wall inside a drywall structure attached to the masonry Poroton 49cm (19 inch) wall.
Question 1): Should I choose the gable side that is not above the kitchen on the ground floor with the exhaust hood, or do kitchen odors dissipate well enough over two floors so that you don’t end up pulling kitchen air into the ventilation unit in the gable?
Question 2): Are there any experiences with this approach of having an insulated small room? It seems the insulation on top of the ceiling would be left out in this area to allow heat from the first floor to rise into the small room. Is that sufficient to keep the insulated space warm enough just from the heat of the rooms below?
Looking forward to hearing your thoughts.
Best regards
I have two questions regarding the following proposal from our architect:
We are planning a two-story house with a pitched roof and a basement. He recommends installing the central mechanical ventilation system with heat recovery in the attic (this avoids breaking through the basement wall and having a "little tower" in the garden). However, the attic is intended to be outside the thermal envelope (insulation will be added on top of the concrete ceiling of the first floor). Since the attic can get quite cold without insulation, and according to him the ventilation system does not work well in rooms colder than 10°C (50°F), we are advised to build an insulated small room for the ventilation system on one gable wall inside a drywall structure attached to the masonry Poroton 49cm (19 inch) wall.
Question 1): Should I choose the gable side that is not above the kitchen on the ground floor with the exhaust hood, or do kitchen odors dissipate well enough over two floors so that you don’t end up pulling kitchen air into the ventilation unit in the gable?
Question 2): Are there any experiences with this approach of having an insulated small room? It seems the insulation on top of the ceiling would be left out in this area to allow heat from the first floor to rise into the small room. Is that sufficient to keep the insulated space warm enough just from the heat of the rooms below?
Looking forward to hearing your thoughts.
Best regards
annab377 schrieb:
My question is: if I cook downstairs and vent the kitchen air out of the house through the range hood, is the distance from the ground floor to the attic enough if I bring fresh outside air into the attic directly above the exhaust vent? This has been correctly understood by more than just me.
annab377 schrieb:
Whether the kitchen odors will mix sufficiently with the air outside the house so that I don’t end up sucking the kitchen smells back in through the mechanical ventilation system. Kitchen odors are not hot enough to rise straight up – not even in completely still air. By the time the air reaches an intake in the gable, the situation has already changed significantly.
annab377 schrieb:
In the attic, wouldn’t it be better to go through the gable wall side rather than through the roof itself? Creating an opening in the wall is structurally much simpler than one through the roof covering. After all, the exhaust air isn’t flue gas, so its outlet doesn’t need to be a chimney. Of course, wind can sometimes press against the gable, but that’s not a problem. The proposed solution is neither unusual nor a first-time case—you can safely go ahead with it.
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Mycraft schrieb:
The exhaust air from a kitchen range hood is actually unrelated since it forms a separate system. From what I understand from the explanations, an automatic shutdown of the mechanical ventilation system should be planned when the range hood is running. Yes, of course, the exhaust air / the kitchen range hood is unrelated to the mechanical ventilation system, and they are two separate systems. The question was whether kitchen odors, which are vented outside the house via the range hood located 1.5 floors above, could be drawn back into the house through the mechanical ventilation system. But as @11ant already mentioned, these will likely mix with the outside air even in calm wind conditions, so they should not be drawn back into the house through the mechanical ventilation.
And yes, thanks for all the answers. So, there should be no problem with insulating that small room in the attic.
@Mycraft, what does your 2 m (6.5 ft) distance refer to? From what I understand, it refers to the distance between the supply and exhaust air openings of the mechanical ventilation system, or you can simply use hoods from manufacturers like Vallox.
@Golfi90, you have decided on fully insulating the attic. That is probably always more expensive than adding insulation from above the ceiling. Do you now actively heat the attic as well, and what do you use it for? We basically only need it for storage, so a full insulation would probably not make financial sense?
Yes, it is doable. However, you will still have to live with some strong odors (unless you use activated carbon filters). In other words, any type of open fire nearby or even a lit fireplace will be noticeable inside the house, as the controlled ventilation system will draw the smells inside.
Yes, this is a general issue with mechanical ventilation systems. It occurs to me that a mechanical ventilation system in the basement, which draws air through an intake tower located just above ground level (although admittedly less visually appealing), would likely draw in fewer barbecue odors than a system in the attic.
Barbecue and smoke odors are more likely to reach the second floor or attic than the intake situated about 1 meter (3 feet) above ground level next to the house. Ideally, a hedge between the properties would help keep most of the odors away at ground level.
Barbecue and smoke odors are more likely to reach the second floor or attic than the intake situated about 1 meter (3 feet) above ground level next to the house. Ideally, a hedge between the properties would help keep most of the odors away at ground level.
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