Kitchen extractor vents and air tightness

[LnP]

What’s the best way to manage removing cooking fumes, smells and steam in an airtight house with MVHR?

 

is there a way to have an extractor vent to outside the house? Is a venting hob the only solution? I assume it’s not a good idea to extract directly into the MVHR?
 

Thanks

[ProDave]

Recirculating cooker hood with carbon filters and MVHR extract vent nearby but not directly coupled.  Boost the MVHR rate while cooking if you want to.

[JohnMo]

8 minutes ago, ProDave said:

Recirculating cooker hood with carbon filters and MVHR extract vent nearby but not directly coupled.  Boost the MVHR rate while cooking if you want to.

As Dave says, but I have the extract at the other end of the kitchen and have a foam filter mesh inside to catch anything that may get into the duct work. Rarely need to use the cooker hood.

[Conor]

Recirculating hob / extractor. No need to complicate things with direct extract or ducting in to the MVHR system with complex and expensive filters etc.

[Kelvin]

We have a recirculating hob with grease and  carbon filters with a nearby MVHR extract. I’ve set the hob to manual operation of the extractor though rather than it automatically coming on with the hob. 

Edited April 1 by Kelvin

[dpmiller]

Bog-standard (but powerful) extractor, and MVHR extract point over the sink but near the cooker.

 

Normal steamy cooking is dealt with just fine by the MVHR, but on the occasions that I want to fry or stirfry I whack on the big fan. Ensures the oils aren't heading into the ducts, and I really don't care if flow is unbalanced for half an hour every now and then...

[LnP]

2 hours ago, dpmiller said:

Bog-standard (but powerful) extractor, and MVHR extract point over the sink but near the cooker.

 

Normal steamy cooking is dealt with just fine by the MVHR, but on the occasions that I want to fry or stirfry I whack on the big fan. Ensures the oils aren't heading into the ducts, and I really don't care if flow is unbalanced for half an hour every now and then...

Is that an extractor to the outside? Does it affect the air tightness?

Thanks

[dpmiller]

3 hours ago, LnP said:

Is that an extractor to the outside? Does it affect the air tightness?

Thanks

Yes, an extractor to the outside. It's through a gravity flap which has a rubber seal on and is pretty airtight, certainly not entertaining any backflow. It will very rarely (depending on wind direction) flap open briefly on very heavy gusts and so I've considered going to a motorised damper, but it's just not bad enough to really worry about...

[Blooda]

16 hours ago, Conor said:

Recirculating hob / extractor. No need to complicate things with direct extract or ducting in to the MVHR system with complex and expensive filters etc.

Plus one

 

[Nick Laslett]

There is nothing wrong with recirculating cooker hoods. But if you can easily have an airtight, automatic cooker hood venting outside, why wouldn’t you?

 

For me this is similar to the issue of MVHRs sucking in bonfire smoke. Not an issue for many, but not something you want to suffer if you don’t have to.
 

Part of the joy of self building is that you can indulge certain preferences that may not pass a normal cost benefit analysis. 
 

Nearly all the reading I did on MVHRs pointed to recirculating cooker hoods as the solution for cooking vapours. But there are some interesting dissenting voices. 
 

https://www.treehugger.com/passive-house-institutes-look-kitchen-fans-less-exhaustive-4857372

 

Here is the Passive House guide on kitchen ventilation.

 

https://passiv.de/downloads/05_extractor_hoods_guideline.pdf

 

 

[CalvinHobbes]

On 02/04/2024 at 18:24, Nick Laslett said:

There is nothing wrong with recirculating cooker hoods. But if you can easily have an airtight, automatic cooker hood venting outside, why wouldn’t you?

 

For me this is similar to the issue of MVHRs sucking in bonfire smoke. Not an issue for many, but not something you want to suffer if you don’t have to.
 

Part of the joy of self building is that you can indulge certain preferences that may not pass a normal cost benefit analysis. 
 

Nearly all the reading I did on MVHRs pointed to recirculating cooker hoods as the solution for cooking vapours. But there are some interesting dissenting voices. 
 

https://www.treehugger.com/passive-house-institutes-look-kitchen-fans-less-exhaustive-4857372

 

Here is the Passive House guide on kitchen ventilation.

 

https://passiv.de/downloads/05_extractor_hoods_guideline.pdf

 

 

Excellent links, thanks.

So hitting this issue ourselves. We do a lot of stir frying and I have a well used chip pan, in the past recirculaing hood have proved miserable and inadequate for our usage. Rather than undoing everything with effectively a hole in the wall, what about this? 

https://luxairhoods.com/Cooker-Hood-Ducting-150mm/cooker-hoods-outside-vents-grilles-external/Airtight-Ducting-System-Kits/New-ducting-Thermobox-150mm-heat-retention

[JohnMo]

20 minutes ago, CalvinHobbes said:

well used chip pan

Get an air fryer - way better chips. Took me awhile to be converted 

 

 

[dpmiller]

38 minutes ago, JohnMo said:

Get an air fryer - way better chips. Took me awhile to be converted 

 

 

just like they use in chippys then?

[JohnMo]

6 minutes ago, dpmiller said:

just like they use in chippys then?

Funny you say that the was a comparison done in a football ground, where they installed an industrial sized air fryer.  The air fryer chips didn't go down any worse than the traditional oil fried chips in a blind test with the football fans. 

 

As I said took a long time to be converted but if you like crispy chips they are great.

[saveasteading]

51 minutes ago, dpmiller said:

like they use in chippys then?

Another advantage will be in saving the cost of all that oil, and the chance that they use it too long.

Oh and we would get more potato than oil. I wonder how much oil is in a chip.

Air fried chips are great esp after practice. Precooked potato in the microwave then into the frier.

It's just a kettle element and a fan.

[JohnMo]

16 minutes ago, saveasteading said:

Precooked potato in the microwave

Do my jacket pots the same way, in microwave for 2 pots for 10 mins, in air fryer for 20 to 30min.

[Kelvin]

We debated for some time about whether to extract to outside or use a recirculating hob but this was more about air quality in an open plan design than air tightness. Because of some aesthetic design decisions we decided on a recirculating hob with the caveat that we hardly ever fry food. We will also need to ensure we replace/clean the filters much more regularly than any other house we’ve lived it. Most cooker extraction hoods are far too high above the cooker to be effective anyway even if they are extracting externally. If you look at  commercial kitchens you’ll often see the hood is much closer to the bob than in domestic kitchens. 

[JohnMo]

4 minutes ago, Kelvin said:

Most cooker extraction hoods are far too high above the cooker

Exactly, the Passivhaus article above makes that direct reference. Our I stipulated the height, the installer did what they always do, set it 200mm higher than I stipulated. Didn't pay the final invoice until sorted at their expense - which they did.

[saveasteading]

6 minutes ago, Kelvin said:

hood is much closer to the bob than in domestic kitchens. 

In forehead bashing position!

@Kelvin where are the filters in yours? And they are disposable, not cleanable?

[Kelvin]

2 hours ago, saveasteading said:

In forehead bashing position!

@Kelvin where are the filters in yours? And they are disposable, not cleanable?

Inside the hob. There are two sets of filters. Disposable carbon filters and washable grease filters. 

[saveasteading]

58 minutes ago, Kelvin said:

Inside the hob.

In a cassette that comes easily out?

[Kelvin]

28 minutes ago, saveasteading said:

In a cassette that comes easily out?

They are individual but yes easy to get out. There’s also a container underneath the hob to catch any spills. 

[garrymartin]

Extract from my research notes that might be helpful;

• Recirculating cooker hood with grease (typically steel/aluminium mesh) and charcoal/carbon filters with a MVHR extract vent nearby but not directly coupled.  Boost the MVHR rate while cooking if you want to (current sensor on induction hob cable for automation??)
• Grease filters need cleaning regularly; every 1-3 months
• Charcoal/carbon filters have a lifetime (usually 3-12 months; check manufacturer specifications) and should be replaced
• Try to get a model with grease filters that can go (and fit) in the dishwasher and that will not tarnish, or that can be replaced (should you wish to)
• SMEG, for example, has a Universal Charcoal filter Stainless Steel AISI 304. The filter can be washed in the dishwasher at 50°C (water and suitable detergent) and to dry, put in the oven 180°C for 25 minutes

 

 

[Mike]

Also worth knowing that there is an official rating for how well hoods filter the grease, from A (>95%) to G (> or = to 45%). You may have to dig to find it - some manufacturers don't seem keen to make it easy to find in their literature.

 

 

 

 

[Marvin]

On 01/04/2024 at 20:57, ProDave said:

Recirculating cooker hood with carbon filters and MVHR extract vent nearby but not directly coupled.  Boost the MVHR rate while cooking if you want to.

that is exactly what we have!