Kitchen extractor vents and air tightness

[Kelvin]

On 13/04/2024 at 14:39, Kelvin said:

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

@saveasteading the two removable grease filters are in this caddy. The four replaceable carbon filters are in the second picture with two either side. The third picture shows the grease filter caddy/holder in place. Excuse the dust. 
 

[saveasteading]

18 minutes ago, Kelvin said:

Excuse the dust. 

Not a speckle finish option instead of black?

Useful pics, thanks.

That must be quite  noisy fan to attract the air over there when it wants to rise.

[Kelvin]

😂 yes, it’s a speckled finish.   
 

It is very effective with steam even at a low speed which is quiet.  At full pelt it’s noisy but much the same as a cooker hood. You can configure it to come on automatically or manually. It also runs for a variable period of time after you’ve finished cooking. In the installation manual it mentioned that you can replace the carbon filters with acoustic filters. 

 

 

[LnP]

15 hours ago, Kelvin said:

😂 yes, it’s a speckled finish.   
 

It is very effective with steam even at a low speed which is quiet.  At full pelt it’s noisy but much the same as a cooker hood. You can configure it to come on automatically or manually. It also runs for a variable period of time after you’ve finished cooking. In the installation manual it mentioned that you can replace the carbon filters with acoustic filters. 

 

 

Very helpful thanks!

[Kelvin]

6 minutes ago, LnP said:

Very helpful thanks!

For completeness it extracts to a duct that attaches to the back of the hob and runs down behind and underneath the cabinet. This was a fiddly thing to put together. A bit like the scene from Apollo 13 where they have to make a CO₂ filter out of bits that don’t quite fit. The duct doesn’t come with the hob though so you need to buy that separately and they do different types to suit different installations. 

[Renegade105]

When deciding on an extractor fan in an airtight house, I think your answer is guided by what your priority is.

 

1) IAQ- indoor air quality, both particulates, grease and molecular pollution (go for external vent)

2) Heat loss- (go for a recirculating hood) 

3) MVHR- Forget about using that to clean up the air, the ones you have can't even deal with a firework display or your neighbours log burner 5 streets away, but that's another topic all together.

 

In my opinion, recirculating fans aren't very effective. Yes as the previous post alluded to, pulling steam might work quite well, great, but water vapour isn't a concern if IAQ is your priority. If you care about removing the particles generating when cooking, then the filter and carbon wont do that as they're too small and too coarse. The worry here is you don't actually see the pollutants coming off when you're cooking, you only see the really large particles that aren't particularly harmful as your cilia and hairs lining your respiratory tract can deal with them. Its the tiny particulates that cross your BBB (blood brain barrier), the ones that easily are absorbed through your lungs that you need to watch for, and you have no chance filtering out the molecular pollution, unfortunately the carbon needs a long contact time to work...a thin bed of carbon wont do.

 

Did you know none of the kitchen extractors are really regulated in any way. Apart from some distance above the hood and some European energy limits on the fan, its pretty much do whatever you like.

 

In the end, I believe your health should come first, that means losing your warmed expensive air and for that you get a slightly colder home but you and your family are hopefully alive for longer to enjoy said cold house for longer.

 

Keep it simple.

 

In my opinion, an extractor hood, and a remote fan away from the user so noise doesn't limit how fast you run it when its required. This means a lot of the time a custom hood, and for that you need quite a large duct too. Remember to wire up a light switch and fan controller near the user in the kitchen, and make the wife promise to open the window if she wants to cook anything.

 

A chef is in the most harmful zone , directly above/in front of the pollutant source, so you have better create a good negative pressure zone there to scavenge away the harmful stuff away from them, just like you would if you were soldering, there's really not much difference.

 

Just my 2cents to anyone considering their new home or refurb.

 

 

 

[JohnMo]

9 hours ago, Renegade105 said:

Keep it simple.

 

In my opinion, an extractor hood, and a remote fan away from the user so noise doesn't limit how fast you run it when its required. This means a lot of the time a custom hood, a1gnd for that you need quite a large duct too.

Sorry how is that "keep it simple" a thing but simple.

 

9 hours ago, Renegade105 said:

believe your health should come first,

Easy answer - Keep it simple - don't fry everything. Then you don't generate the pollutants.

 

[Renegade105]

I can do better then that…don’t cook at all that way you don’t have any pollutants.

 

beleive it or not, even induction jobs create pollutants…heat provides the enthalpy change required to create chemical reactions too..just saying. 
 

I know this is a bit of a tricky subject, and as I said I am just giving my 2 cents, especially for people who use the kitchen a fair bit.

 

[G and J]

We fry very little and still over time there is trace evidence of grease build up on our stainless steel cooker hood, so I take it as a given that there are nasties to be ejected/captured.

 

We are not having a hob in our kitchen area as it is part of the big living area.  Instead a hob will be used in our utility room, one wall of which is external and has a narrow and rarely used alley next to it, so perfect for dumping stinkies.

 

So my thinking is maybe wall mounted fan ducted to collector above hob.  But when this runs does it unbalance the MVHR?  The direct air woodburner is in another room but will it blow back if one opens the door to load wood when the extractor is running?  Do I need an auto opening inlet also in the utility room to balance things?  Will the extra holes in my otherwise nicely air tight house undermine all my careful design/taping/etc?

 

Yours truly, Worried of Suffolk.

[Mr Punter]

10 hours ago, Renegade105 said:

In my opinion, an extractor hood, and a remote fan away from the user so noise doesn't limit how fast you run it when its required. This means a lot of the time a custom hood, and for that you need quite a large duct too. Remember to wire up a light switch and fan controller near the user in the kitchen, and make the wife promise to open the window if she wants to cook anything.

 

That is what I have.  I used a chimney type extractor, took out the motor and connected to the ducting to an inline fan sited in a cupboard on the roof terrace.

[JohnMo]

This what Passivhaus say on the subject 

 

05_extractor_hoods_guideline.pdf

[Renegade105]

Consider these points and again base it on what’s important.

 

1) where in those guidelines does it really discuss IAQ, or even test it..shouldn’t guidelines be based on that?

2) filter lifetime are 1-3 months..so what happens at the end of 1-3 months? Are filters 100% blocked? How would you know if you need to change 1 or 3 months? Would you be happy buying a car with a fuel gauge that says refill at 1-3 months? 
 

we need to start questioning the norm guys..it all stinks.

 

[Renegade105]

And finally..carbon filters have a dwell time to work..and that is how carbon filters work.

 

carbon coated media (which is what you can buy) are saturated very quickly,,and they don’t operate in high humidity..something to consider when admiring the steam doing a 180 degree turn.

[Renegade105]

Hi.

 

yes you can do a motorised inlet valve to allow balancing….or open a window?

 

 

[G and J]

So I need:

 

an in-line fan.

 

two mains operated dampers, preferably return to closed if power is removed for simplicity.

 

one of these vents to the alley above head height, ducted via the auto-damper (tm) to the collector above the hob via the inline fan.

 

the other inlets at knee height in the alley and feeds ducts which outlet into the room at kickboard level maybe.  
 

Hmmm, still much opportunity for imbalance , but it mimics opening a window and that’s ok according to the PH guys.  Just wear a big coat when cooking in winter….

[G and J]

and then if I add a second fan and heat exchanger I will have invented the assisted airflow energy retention system.

 

This time next year Rodders, we’ll be miwionaires….

 

Maybe not…..  😕 

[Renegade105]

I think usually for the extract vent flaps would suffice however a motorised one would be better. Just a bit more complicated and expensive.

 

for the inlet, check out iris dampers..have a better control of the flow however I have seen that you might need a fan in any case for this make up air circuit.

 

seriously a window might be so much easier if possible. You can even get motorised window openers for max feel levels.

[Renegade105]

Don’t supply to your plinth, you will get cold toes.

[JohnMo]

1 hour ago, Renegade105 said:

filter lifetime are 1-3 months..so what happens at the end of 1-3 months? Are filters 100% blocked? How would you know if you need to change 1 or 3 months? Would you be happy buying a car with a fuel gauge that says refill at 1-3 months

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.

 

 

 

1 hour ago, Renegade105 said:

we need to start questioning the norm guys..it all stinks

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.

[G and J]

I think the final answer will be to simply putting a big standard recirculating cooker hood in, together with a grease filter on the MVHR extract vent for that room.  However I do like to work through the options to hopefully make good, informed decisions.

 

The emotionals are difficult here for me.  I’m a fresh air freak and currently live in a well insulated wind tunnel, so major purge type ideas resonate even if they are not really needed.

[dpmiller]

2 hours ago, JohnMo said:

Carbon filter goes in the oven to be regenerated.

 

does that not create smoke that needs :ahem: extracted?

[JohnMo]

8 minutes ago, dpmiller said:

 

does that not create smoke that needs :ahem: extracted?

Not that I noticed. As said we barely use the cooker hood, so regen are few and far between.

[G and J]

11 minutes ago, dpmiller said:

 

does that not create smoke that needs :ahem: extracted?

You might be thinking of my baking skills.  In a moment of inspiration I realised I should plumb my oven directly into the MVHR.  😕 

[JohnMo]

11 minutes ago, G and J said:

You might be thinking of my baking skills.  In a moment of inspiration I realised I should plumb my oven directly into the MVHR.  😕 

Perhaps you could heat the whole house from the oven? 😜 

[G and J]

2 minutes ago, JohnMo said:

Perhaps you could heat the whole house from the oven? 😜 

Good plan.  I like the gently warming background smell of smoke.  
 

As a child in the 60’s I was a three packet a day passive smoker so I guess it brings back fond memories.  Well, memories anyway.  
 

Actually by Jove that’s it.  I don’t want a passive house - I want a passive smoker house - everything needs to be various hues of brown.  Our design is finally complete!