Externally ducted cooker hood with MVHR

[Mark Hanson]

Hi, I am installing a whole house MVHR but I not impressed with the idea of using a recirculating cooker hood, especially when cooking strong smelling foods such as currys etc. Recirculating hoods only work to a point and the thought of spreading pungent cooking smells through the whole house is a no no..

I have been looking at a couple of options to give me a separate external vented Cooker hood. I option is to build a motorised airtight damper into the round ducting network. The damper is opened as the fan is turned on and subsequently closes when extractor is turned off. 

Another Interesting idea I have seen is the Luxair automatic airtight vent which opens when there is a pressure of above 150Pa, I.e fan is on speed 1, then closes to give a airtight seal again.

If I used either option I would turn off MVHR and kitchen extract only for cooking period then turn MVHR back on. 

General daily living such as boiling veg and steam from kettle i would just use MVHR ventilation.

Has any one used these solutions along with their MVHR, or come up with other solutions other than cooking curry out in the garden

 

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F381900534260      (motorised damper link)

 

https://luxairhoods.com/kitchen-extractor-hoods-ducting-and-vents/Airtight-Ducting-System-Kits

 

[Jeremy Harris]

We have MVHR.  I can say with confidence that even with no cooker hood we get no cooking smells outside the kitchen, ever.  What smells are created when cooking dissipate quickly as the air gets changed via the MVHR.  If we feel there may be a smell problem we just hit the boost button to clear the smell more quickly, but most of the time we don't bother.  Right now there's cauliflower and broccoli being cooked in the kitchen, and the door to the kitchen is partially open and around 6 feet from where I'm sitting.  There is no smell here at all, absolutely nothing, and the MVHR isn't even on boost.

 

I did put provision in the ceiling to fit a hood, both wiring and a bit of thick plywood behind the plasterboard as a strong point, but I never got around to installing one, as it seems it's not needed.  Came as a bit of a surprise, TBH, as in our old house we were plagued with cooking smells permeating the whole house, even with an extractor hood above the hob, that was ducted directly outside.

[Ed Davies]

48 minutes ago, Mark Hanson said:

and the thought of spreading pungent cooking smells through the whole house is a no no..

 

Why would cooking smells be spread through the whole house if you have an extract vent in the kitchen, which you would, of course?

 

49 minutes ago, Mark Hanson said:

If I used either option I would turn off MVHR and kitchen extract only for cooking period then turn MVHR back on. 

 

Would it make sense to turn off the extract side of the MVHR but leave the supply side running? Perhaps even boost the supply side. Do MVHR controller allow that?

[JFDIY]

I looked around a lot on this subject, downloaded a load of suppliers info and commissioning manuals and the only company I could find who'd got their head around it was vent-axia. Depending on the unit (not all models do it), you can set up a cooker mode, the documentation suggests it needs to link to their hood, but it can be wired into a switch.

When you switch cooker mode you the unit bypasses the heat exchanger to prevent fouling, and ramps up the extract to 100% and supply at 30% are default settings, but fully user configurable.

 

I've just installed a kinetic plus B, and intend to have a couple of grease filters above hob and some valves that open to bypass any restrictors in extract ducting in the kitchen, so the extra extract is above hob and oven not around whole house.

 

[MJNewton]

1 hour ago, Mark Hanson said:

Hi, I am installing a whole house MVHR but I not impressed with the idea of using a recirculating cooker hood, especially when cooking strong smelling foods such as currys etc. Recirculating hoods only work to a point and the thought of spreading pungent cooking smells through the whole house is a no no..

 

I might've misunderstood what you're saying, but picking up on this last point note that the supply and extract sides of an MVHR system are separate and so any smells picked up by the latter don't pass to the former. This is one of the main reasons the intake and exhaust terminals are always sited far apart. 

[Ed Davies]

2 hours ago, JFDIY said:

When you switch cooker mode you the unit bypasses the heat exchanger to prevent fouling, and ramps up the extract to 100% and supply at 30% are default settings, but fully user configurable.

 

Interesting. Rather the opposite of what I had in mind: perhaps supply to 100% and extract to 30% would be better if you're switching on a separate extractor but if it's configurable to do that that'd be OK. Having a completely separate kitchen extract path might be simpler than valves and bypasses.

 

I don't quite see the logic of reducing supply to 30%, though. Doesn't that just depressurise the house so the other 70% is made up from random leakage?

 

A bit theoretical for me as, for most of the cooking I do, I'm pretty sure that a recirculating hood will be sufficient.

[ProDave]

Same as above. No cooker hood yet, mainly because we have not yet seen an island cooker hood that we like yet. The cable and fixing points are there for it.

 

Our kitchen is part of the largest ground floor room, what is often called a "family room" by some people.  So it has an MVHR inlet an one end and an mvhr extract at the kitchen end.  I have just this weekend got around to balancing the mvhr system and made sure the inlet and outlet rates for that room are balanced.

 

Like others cooking smells don't seem to spread, and I continue to delight in the good air quality throughout the whole house.

 

Until you have lived in a house with mvhr, it is hard to understand just how well it works at keeping the house air nice and fresh.

[JFDIY]

3 hours ago, Ed Davies said:

Interesting. Rather the opposite of what I had in mind: perhaps supply to 100% and extract to 30% would be better if you're switching on a separate extractor but if it's configurable to do that that'd be OK.

 

Had a bit of a play with the settings, seems you can set the inlet to any figure you like (100% If desired), but the commissioning manual states the extract must be higher than boost rate, I tried it lower and it accepted the figure without any warning on display. I don't currently have the cooker mode switch in place so couldn't try for real to see if it defaulted to boost extract by over-ruling the set-point.

 

So yes, you could have a separate extractor unit to the mvhr and try and compensate by increasing inlet flow. It would however be cold air input to the house though as the summer bypass is opened on the cooker hood function.

[Adsibob]

On 17/11/2019 at 15:38, ProDave said:

Same as above. No cooker hood yet, mainly because we have not yet seen an island cooker hood that we like yet. The cable and fixing points are there for it.

 

Our kitchen is part of the largest ground floor room, what is often called a "family room" by some people.  So it has an MVHR inlet an one end and an mvhr extract at the kitchen end.  I have just this weekend got around to balancing the mvhr system and made sure the inlet and outlet rates for that room are balanced.

 

Like others cooking smells don't seem to spread, and I continue to delight in the good air quality throughout the whole house.

 

Until you have lived in a house with mvhr, it is hard to understand just how well it works at keeping the house air nice and fresh.

@ProDave did you ever get around to installing a cooker hood, or do you continue to just rely on the MVHR?

[ProDave]

5 minutes ago, Adsibob said:

@ProDave did you ever get around to installing a cooker hood, or do you continue to just rely on the MVHR?

Yes, an island hood from Howdens, recirculating. I don't seem to haver taken a photograph of it.

 

 

[saveasteading]

9 minutes ago, ProDave said:

an island hood from Howdens, recirculating.

I was taught that we first make the building airtight, then add ventilation, which is controlled unlike draughts.

I think our chefs will require an extract fan, but surely they are available with electrified shutters.