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Venting a gas hob through an outside wall (horizontal discharge)
samizdat
Posts: 398 Forumite
tl;dr Gas hob by an external wall - can I just vent it straight through this wall by putting a high-powered fan on the wall powered by an external motor?
Consider a small (600 square foot) raised ground floor apartment in a four storey Victorian semi-detached brick building.
In a corner of the building (unattached side), there is a tiny kitchen with a ceiling height of only about 2.1 metres, because above it is the mezzanine landing of the communal staircase. In this kitchen, which is partially open plan to the main living room, there is a gas hob (60cm wide) with a recirculating visor-style hood above it.
The kitchen is about to be replaced (floor and cabinets), and I am considering options for a new cooker hood, ideally vented through the side wall of the building. Above the visor-style cooker hood, there is currently a storage cabinet.
As this is a corner location, there is the benefit that one side of the hob is fully enclosed, improving the fluid dynamics of the set-up. I have calculated that makeup air (that which replaces exhaust air) could flow as fast as 45 feet per minute (823 metres per hour) with a fan rated at 615 cubic metres per hour, well within the range of domestic appliances, and an acceptable peformance at, say, 400 m3/hour would be achievable in theory without much noise, subject to limitations of static pressure (but the house is old and "leaky" in ventilation terms).
Storage space in the kitchen is very scarce, and noise is problematic as it affects the main living area.
I am wondering whether a solution could be to drill a large hole through the side wall of the building about 75 to 90 cm above the hob, and to install a centrifugal fan and motor on the exterior of the building to exhaust the cooking fumes. (The open sides of these buildings are mostly devoid of windows, and are essentially just access paths between the street and rear gardens. Noise might be the only potential problem.) Some sort of fire-resistant canopy could be constructed to capture the rising fumes. Weather-proofing and a grease filter could I hope be integral to the fan, with cleaning\maintenance by ladder from outside the building, or through the hole in the wall.
Commercial products appear to be focused on mass-produced, integrated devices and upon vertical discharge and ducting, but I am unclear whether there is any purpose to ducting (or vertical discharge) except to reach the exterior of a building, whereas this hob is already on an outside wall.
Even remote motor devices appear, at least from a marketing perspective, to be designed to operate only with a very limited range of hoods from the same manufacturer.
Furthermore, the cupboard above the hob is useful space, and anyway the ceiling height appears to be close to the limit when I examine technical drawings, especially considering a vertical ducting pathway would have to be bent 90 degrees very close to any built-in motor and fan assembly, which I understand to be sub-optimal in terms of noise, flow, and static pressure.
Please advise on a solution that minimises use of space and noise, both within the apartment but also exterior noise that might disturb neighbours. For example, if an external motor is rated at 60 db(A), do you think that would disturb this urban neighbourhood, and how much could one realistically reduce this noise through adding insulation?
A part of the mezzanine landing above the kitchen (and hob), belongs to the apartment, and is occupied by a gas boiler, a washing machine, and various items used for cleaning (e.g. a vacuum cleaner).
I suppose in theory a chimney could go through the ceiling into the mezzanine landing space, either beneath its floor or further, subject to the presence of joists, fire barrier concerns, and cost.
Consider a small (600 square foot) raised ground floor apartment in a four storey Victorian semi-detached brick building.
In a corner of the building (unattached side), there is a tiny kitchen with a ceiling height of only about 2.1 metres, because above it is the mezzanine landing of the communal staircase. In this kitchen, which is partially open plan to the main living room, there is a gas hob (60cm wide) with a recirculating visor-style hood above it.
The kitchen is about to be replaced (floor and cabinets), and I am considering options for a new cooker hood, ideally vented through the side wall of the building. Above the visor-style cooker hood, there is currently a storage cabinet.
As this is a corner location, there is the benefit that one side of the hob is fully enclosed, improving the fluid dynamics of the set-up. I have calculated that makeup air (that which replaces exhaust air) could flow as fast as 45 feet per minute (823 metres per hour) with a fan rated at 615 cubic metres per hour, well within the range of domestic appliances, and an acceptable peformance at, say, 400 m3/hour would be achievable in theory without much noise, subject to limitations of static pressure (but the house is old and "leaky" in ventilation terms).
Storage space in the kitchen is very scarce, and noise is problematic as it affects the main living area.
I am wondering whether a solution could be to drill a large hole through the side wall of the building about 75 to 90 cm above the hob, and to install a centrifugal fan and motor on the exterior of the building to exhaust the cooking fumes. (The open sides of these buildings are mostly devoid of windows, and are essentially just access paths between the street and rear gardens. Noise might be the only potential problem.) Some sort of fire-resistant canopy could be constructed to capture the rising fumes. Weather-proofing and a grease filter could I hope be integral to the fan, with cleaning\maintenance by ladder from outside the building, or through the hole in the wall.
Commercial products appear to be focused on mass-produced, integrated devices and upon vertical discharge and ducting, but I am unclear whether there is any purpose to ducting (or vertical discharge) except to reach the exterior of a building, whereas this hob is already on an outside wall.
Even remote motor devices appear, at least from a marketing perspective, to be designed to operate only with a very limited range of hoods from the same manufacturer.
Furthermore, the cupboard above the hob is useful space, and anyway the ceiling height appears to be close to the limit when I examine technical drawings, especially considering a vertical ducting pathway would have to be bent 90 degrees very close to any built-in motor and fan assembly, which I understand to be sub-optimal in terms of noise, flow, and static pressure.
Please advise on a solution that minimises use of space and noise, both within the apartment but also exterior noise that might disturb neighbours. For example, if an external motor is rated at 60 db(A), do you think that would disturb this urban neighbourhood, and how much could one realistically reduce this noise through adding insulation?
A part of the mezzanine landing above the kitchen (and hob), belongs to the apartment, and is occupied by a gas boiler, a washing machine, and various items used for cleaning (e.g. a vacuum cleaner).
I suppose in theory a chimney could go through the ceiling into the mezzanine landing space, either beneath its floor or further, subject to the presence of joists, fire barrier concerns, and cost.
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Comments
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Less is more0
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My gas hob has a cooker hood above but the motor in the hood has never worked so I just open a window if I need ventilation.0
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The visor type cooker hoods I've seen can be set to either recirculate or to vent externally, and many have blanking plates so they can be set to vent vertically upward, or horizontally through a vent at the back, straight out through a wall if the necessary vent has been installed.
I'd suggest going on a manufacturer's website and reading the installation instructions for a few different models - you can certainly get a hood that does what you want.0 -
This might work. Expensive, but operating parameters seem very good (air volume, noise). It has an option for horizontal discharge.
https://www.miele.co.uk/domestic/cooker-hoods-2484.htm?mat=10568370&info=download#sketch
I wonder a bit about noise transmission to the outside in this scenario, because the motor would be really just the thickness of the hole in the wall away from the outside World.
Do I make a bigger hole in the wall so I can lag the exit duct, or would that be counterproductive?0
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