Kitchen extractor vents and air tightness

[JohnMo]

33 minutes ago, G and J said:

don’t want a passive house - I want a passive smoker house

Just paint the ceiling near the sofa a slightly darker shade of brown. Now you are finished. Here to help 🚭🙂

[G and J]

35 minutes ago, JohnMo said:

Just paint the ceiling near the sofa a slightly darker shade of brown. Now you are finished. Here to help 🚭🙂

When, as an adult, having moved away from the smokehouse that formed me, I helped decorate my parents living room - I started by washing the ceiling.  I could not believe what was coming off.  Perhaps that’s why I’m now a fresh air freak (who subconsciously likes brown).  

[Renegade105]

@ G and J.  😂 that had me in stitches.

 

I’m used to dealing with nuclear dust, asbestos, molecular pollution such as NOx and all within a regulated environment where standards and testing matter hence why I chirped into the discussion.

 

its perfectly normal to get this push pack sometimes as I get it from my builders!

 

Typical comments I’ve had are: what’s the point in an air tight house, buildings need to breathe…ASHP will never work, how will you get hot water…MVHR..well that’s obviously a rich person con…..£100 roll of tape…are you insane….VOC’s….they don’t do anything…PM1 particles, that’s fake…NOx …my diesel is eco…electric cars…total scam…Solar? Never gonna work in this country…Wood fiber insulation…what a con….ICF…I’ve obviously lost it now,  triple glazing (show off), and finally the kitchen extractor 😬.

 

list just goes on.

 

 

 

[Renegade105]

10 hours ago, JohnMo said:

Grease filter goes in dishwasher. Carbon filter goes in the oven to be regenerated.

 

As said before we hardly use the extractor at all and we find zero need except for really smelly stuff.

 

Our kitchen MVHR filter sock (after 6 months installed - top is the outside the duct side, bottom is inside, showing dust ect from the room.

 

 

 

Why do we need to question the norm? Where is your evidence that a normal house (with MVHR or other suitable ventilation system) suffers from poor IAQ. Most houses don't even ventilate correctly and suffer mould, which I suspect is way more hazardous to health - than an extract on recirculation with decent grease and carbon filter, positioned at the correct height for effective performance, so you don't need to run the fan at full speed.

 

Everyone is free to do what ever they feel is correct for them. Personally think everything is getting OOT, I have said my view, so will leave it there.

https://passivehouseplus.ie/magazine/insight/hell-s-kitchen-why-cooking-can-destroy-indoor-air-quality
 

A simple example worth reading.

[JohnMo]

21 minutes ago, Renegade105 said:

’m used to dealing with nuclear dust, asbestos, molecular pollution such as NOx and all within a regulated environment where standards and testing matter hence why I chirped into the discussion

So tell us about a normal (well maybe not that normal) house that is pretty airtight, has MVHR, triple glazing, ASHP, also made of ICF, and how the hob and using it. actually requires a ducted extract. What advantages we get to IAQ overall and for the 30 mins a day you may spend cooking? 

 

Most kitchen cooking hoods are set way to high from the hob to be effective, either at extracting or recirculating. So in most situations the bad stuff just bypasses the hood anyway.

 

Main difference from anything commercial, is the fact no one spends that much time actually cooking every day. So circumstances, cooking temperatures are not compatible. Understand the need in a commercial kitchen, but not sure I follow the thread in a residential property.

[Kelvin]

We’ve discussed this before on here. ‘Most folk’ don’t even bother running the extractor fan at all as it’s too noisy. If they do then how many run them for the recommended 10 minutes after cooking? They also don’t clean them regularly enough or replace the filters often enough. Induction hobs are the healthiest (as in least harmful) cooking hob. We fry infrequently (once a week to make omelettes), don’t have a toaster, and I’ll often open the door beside the kitchen if I am going to fry anything for longer. We do have a Sunday roast every week which likely does raise the indoor air pollution. It’s my intention to fit an air quality  sensor just to see how bad it gets. It was one of negatives about building an open plan house. 

[Renegade105]

My final input into this thread then.

 

1) I’m not sure I can comment on if an extractor is even required or not. Apart from building control, I suppose if someone doesn’t even cook, then it’s not a big issue. Each to their own which is fine.
 

2) finally, MVHR have very coarse filters that leak a lot..they don’t have a HEPA filter so all the harmful PM1 and 0.1 (mainly those 0.1-0.3 microns particles) just get dumped into the rest of your house, so you dilute it within the envelope of the home. As you will likely have an airtight house with a low Air Change per Hour (currently mostly set at around 0.3 ACH, it will take officially around 3.3 Hours for all of those nasties from the 10 mins of cooking to leave your home..and that’s not taking into account mixing and stalling of air currents within rooms. 
 

3) I have a final thought, if I had a petrol generator and fired it up in my house for 1minute a day and had the exhaust go into my MVHR, is that ok? I mean I can turn my generator on outside and leave it running for an hour so what’s the bumig deal if it’s inside and connected to my fancy MVHR?

Edited July 28, 2024 by Renegade105

[JohnMo]

22 minutes ago, Renegade105 said:

finally, MVHR have very coarse filters that leak a lot..they don’t have a HEPA filter so all the harmful PM1 and 0.1 (mainly those 0.1-0.3 microns particles) just get dumped into the rest of your house

That's not how MVHR works.

 

Extract air only goes outside, it goes via a heat exchanger, air going out and air coming in, are on different sides of a heat exchanger and never mix. Air taken from the kitchen ends up outside and cannot go via other rooms or be distributed around the house.

 

 

[Kelvin]

44 minutes ago, Renegade105 said:

 

 

2) finally, MVHR have very coarse filters that leak a lot..they don’t have a HEPA filter so all the harmful PM1 and 0.1 (mainly those 0.1-0.3 microns particles) just get dumped into the rest of your house, so you dilute it within the envelope of the home. As you will likely have an airtight house with a low Air Change per Hour (currently mostly set at around 0.3 ACH, it will take officially around 3.3 Hours for all of those nasties from the 10 mins of cooking to leave your home..and that’s not taking into account mixing and stalling of air currents within rooms. 
 

 

MVHR units don’t work like that. Both the extract air and input air are on opposite sides of the unit and never mix. I cooked fish the other night and if what you say was true I’d be able to smell it in the other rooms in the house which wasn’t the case. 

[G and J]

14 minutes ago, Kelvin said:

I’d be able to smell it in the other rooms in the house

Oh.  You mean I won’t be able to continue enjoying the aroma of curry night for several days after.  I’m going off this MVHR malarkey….. 😉

[Renegade105]

Yes well I said that for dramatic effect but in all honesty open up your MVHR’s and tell me for sure you don’t have any crossing of air streams…especially as the heat enhangers start to build up.

 

do you know how they test to make sure there is no crossing? Do you know if they test as the cells get a bit blocked?

 

Sorry to question it all.. it it’s what I have found out upon questioning myself.

[Kelvin]

If there was cross leakage of air the smelly fish cooking would be all round the house. I do have my doubts about the IAQ hence why I want to monitor it. 

[ProDave]

I am guilty of the cooker hood too high.  If I had fitted it at the manufacturers recommended height, I would bang my head on it whenever I lean over to stir something in a pan.  and I am not exactly tall.

 

If you are worried about smells from cooking around the house, spare a thought for a previous house I owned where every Sunday I could smell next doors cabbage cooking!!!!

[JohnMo]

1 hour ago, Renegade105 said:

Yes well I said that for dramatic effect but in all honesty open up your MVHR’s and tell me for sure you don’t have any crossing of air streams…especially as the heat enhangers start to build up.

 

do you know how they test to make sure there is no crossing? Do you know if they test as the cells get a bit blocked?

 

Sorry to question it all.. it it’s what I have found out upon questioning myself.

Sorry have you been anywhere near an MVHR unit? Have you tried to remove the heat exchanger, they are a really tight fit. Why to ensure there is no bypass between sides. Not sure how anything would bypass the between inlet and outlet. 

 

Testing for a bit blocked, is called annual maintenance. Removing the HE to flush through and remove debris etc.

[joe90]

18 minutes ago, JohnMo said:

Not sure how anything would bypass the between inlet and outlet. 

An MVHR runs at very little air pressure.

[G and J]

2 hours ago, ProDave said:

I am guilty of the cooker hood too high.  If I had fitted it at the manufacturers recommended height, I would bang my head on it whenever I lean over to stir something in a pan.  and I am not exactly tall.

 

If you are worried about smells from cooking around the house, spare a thought for a previous house I owned where every Sunday I could smell next doors cabbage cooking!!!!

As someone who also bears the scars from looking in pans and forgetting cooker hoods…..

 

Odd methinks that pretty much every kitchen design I’ve ever seen has open areas either side of the hob.  Thinking of the shape of a basic fume cupboard wouldn’t we be better served with the hob boxed in?  Got to be wide enough for handles but surely that would help.

[joe90]

12 minutes ago, G and J said:

As someone who also bears the scars from looking in pans and forgetting cooker hoods…..

 

Odd methinks that pretty much every kitchen design I’ve ever seen has open areas either side of the hob.  Thinking of the shape of a basic fume cupboard wouldn’t we be better served with the hob boxed in?  Got to be wide enough for handles but surely that would help.

I am glad I am short!!! I have seen cookers placed in fireplaces (with the beam/arch raised almost to the ceiling) but I don’t like that. Frankly if the fan is powerful enough it should pull stuff away from the hob.

[dpmiller]

34 minutes ago, joe90 said:

Frankly if the fan is powerful enough it should pull stuff away from the hob.

 

having spent quite a number of years installing and commissioning fumecupboards and BSCs, the airflow required to achieve containment at even quite a small aperture size is large. Conversely the velocity required to allow good capture within a carbon filter is... very low.

 

eg. a schools portable fumehood requires a sash opening of perhaps only 250x600mm (say) so that a low face velocity of 0.3m/s give reasonable containment and time for the filter to adsorb. Vs a ducted fumecupboard  that will be around 1m/s average face velocity to contain within a sash opening of 450x1200mm.

That's a lot of air...

[Renegade105]

3 minutes ago, dpmiller said:

 

having spent quite a number of years installing and commissioning fumecupboards and BSCs, the airflow required to achieve containment at even quite a small aperture size is large. Conversely the velocity required to allow good capture within a carbon filter is... very low.

 

eg. a schools portable fumehood requires a sash opening of perhaps only 250x600mm (say) so that a low face velocity of 0.3m/s give reasonable containment and time for the filter to adsorb. Vs a ducted fumecupboard  that will be around 1m/s average face velocity to contain within a sash opening of 450x1200mm.

That's a lot of air...

Totally agree

[saveasteading]

For a commercial kitchen the fan is huge and very, very noisy. Far more proportionally to cooker size than for most domestic fans and kitchens.  

I suspect that even the next level up for a domestic use would be unacceptably loud in the home environment. 

But why not an additional  extract into the wall behind the hob?

 

 

[G and J]

So, to do the job properly would require industrial vent plant.  Not going to happen. If it’s not worth the piddling extract airflow I’d achieve with an externally venting cooker hood then I might as well just muddle through with a recirculating cooker hood and save myself a cold utility room., relying in the MVHR air change to remove stinky smells.  Simples.