Cooker hood and ventilation problems in flat

[benssson]

Hi all,

We live in a small flat with a open plan kitchen and living area. The problem is that when cooking the room gets quite smelly, smoky and hot. We currently have a re-circulating cooker hood and also a round ceiling vent attached to a central continuous ventilation MEV (which also vents the bathroom). We've replaced the hood filters and turn on the vent boost which helps a bit but not much.

At first I thought all we had to do was install a extracting cooker hood but reading http://www.nuaire.co.uk/blog/residential/the-cookerhood-conundrum/ this seems like a bad idea. Is that right?

What other options do we have?
- Install an extracting cooker hood but have its exhaust Y'd with the MEV's vent and use a damper to avoid blowback?
- Or should we buy a more powerful MEV? Our current MEV is a Titon WCME100 which apparently has a maximum capacity of 325 m3/h.
- Or can we put another another extractor fan in-line to the Kitchen's vent to boost just the kitchen's extraction? I.e kitchen vent -> inline extractor -> MEV. Is this even possible?
- Something else??

I'd be grateful for any help.

Chu

 

[JohnD]

A recirculating cooker hood makes an attractive kitchen ornament but serves no useful purpose.

Extracting fumes and steam directly above the hood is more efficient than extracting in some other part of the room.

An extractor will, by causing suction, prevent the fumes from drifting into other rooms.

If your hood can be vented straight through the wall, that will whisk away cooking fumes best, provided you remember to turn it on before you start cooking.

Your other extractor will be useful for keeping the bathroom well-ventilated. You will need trickle vents or some other means of ventilation so that fresh air can get into your flat to remove the stale moist air that is removed. These vents will be more effective if they are not in the room with the extractor

The ventilator in your link appears to be the sort that does not cause suction, and I have found this type to be relatively ineffective in kitchens and bathrooms as it mixes the air in the room and does not prevent steam and smells from drifting around the home. However if it is ducted so that the incoming air blows into, say, the hall, it may be OK.

 

[benssson]

If your hood can be vented straight through the wall, that will whisk away cooking fumes best, provided you remember to turn it on before you start cooking.

Thanks. the other side if the wall the cooker is on is party to the communal hall so we can't vent straight out unfortunately . The outside wall is about 6m across the room. We're not allowed to make any holes on the exterior wall according to our lease so that was why I was thinking of reusing the existing MEV's exhaust ducting.

 

[JohnD]

OK. You can share ducts, but will need a one-way flap/valve on both the fans.

 

[benssson]

OK. You can share ducts, but will need a one-way flap/valve on both the fans.

Thanks. presumably with the one-way flap/valve I won't have the problems with the hood interfering with the MEV as mentioned in the Nuaire link? will the long duct run (>6m with at least 1 turn) be a problem?

Also, I had another thought - could I install hood with no fan and connect it up to our MEV to just let the MEV do the extraction directly?

 

[JohnD]

a cooker hood, on high speed, is usually pretty powerful.

I don't know how your ducts run but I would be happier with the fan blowing its fumes outside.

 

[ban-all-sheds]

At first I thought all we had to do was install a extracting cooker hood but reading http://www.nuaire.co.uk/blog/residential/the-cookerhood-conundrum/ this seems like a bad idea. Is that right?

If you are (un?)fortunate enough to live in a tightly sealed property, yes.

Yes they have lower running costs, and lower CO2 emissions, but those benefits come at a significant price in day-to-day practicality.

 

[benssson]

At first I thought all we had to do was install a extracting cooker hood but reading http://www.nuaire.co.uk/blog/residential/the-cookerhood-conundrum/ this seems like a bad idea. Is that right?

If you are (un?)fortunate enough to live in a tightly sealed property, yes.

Yes they have lower running costs, and lower CO2 emissions, but those benefits come at a significant price in day-to-day practicality.

Yeh, its pretty air tight. wouldn't the valve/damper mitigate the problem of having an extracting hood?

 

[benssson]

OK. You can share ducts, but will need a one-way flap/valve on both the fans.

Why do I need it on both fans? wouldn't it be enough just on the hood?

 

[Aragorn84]

Presumably because theres a possibility that the hood can create positive pressure in the "intake" ducting to the MEV unit, which would mean that air from the cooker hood could travel back down the intake duct and into the bathroom for example.

 

[ericmark]

Be it a cooker hood or tumble drier there is likely either grease of fluff neither is a good idea in a heat recovery unit.

Second in the main the heat recovery unit does not cause a depression in the room so no problem with open flues. The cooker hood or tumble drier can't be used where there is an open flue unless there is something in place to ensure replacement air.

I have failed to understand why there is more smell when cooking with gas than with electric maybe lack of control with gas? Or may be there is so much exhaust gas produced that the hood can't cope? But I have noticed in my father-in-laws house cooking smells linger longer than in mine. Same design house.

It could also be cooking methods? We use microwave pressure cookers and standard pressure cookers and also closed door grilling with oven fan running and deep fat fiyer plus standard microwave cooking. No cooker hood just velox windows.

It could also be down to the heat recovery unit. The older units had two fans one in and one out the more modern units are using a single extract fan and rely on the depression in the room to draw the air back in. As to which is best design I don't know but the fan could be recirculating the smells before the hood can absorb them.

The point I am making is there are many factors and for some one in the room it may become obvious but remote it's very hard to tell. Yes I will smell food as my wife removes it from the oven but normally only minutes before we eat.

We moved to closed door grilling because of the smoke alarm but so much easier you turn the food just once. Clearly not an option with gas ovens.

Go to a commercial kitchen using gas and the extractors sound like a jet plane but where they use induction the fans are much slower no where near as much air moved. As to if this is because gas is very inefficient and much more heat goes into kitchen rather than the food or it's to remove smells I don't know.

 

[Taylortwocities]

Presumably because theres a possibility that the hood can create positive pressure in the "intake" ducting to the MEV unit, which would mean that air from the cooker hood could travel back down the intake duct and into the bathroom for example.

More than a possibility. The cooker hood will be way more powerful than the MEV unit. That means that the kitchen smells and steam etc will get pumped back through the MEV and into all the rooms that the MEV serves. And you do not want that. It could also stall/reverse the MEV motor, which will die.

So you would need two backdraft flaps. One to stop the situation as above, and one to stop air from the MEV (bathroom, etc) being pushed into the kitchen. And you do not want that, either.

 

[benssson]

Thanks everyone for the help!

So, the plan is to get a extracting cooker hood connected to a backdraft flap and then join the MEV's exhaust duct with a Y piece.

Where do I put the backdraft flap for MEV? do I put two for in MEV intake side (one for the kitchen and one for the bathroom) or just one for at its exhaust?

will backdraft flaps suffice or do I need a electric dampers?

Thanks again everyone!

 

[JohnD]

if you post a diagram showing the route of the ducts we might know.

 

[benssson]

Here's the floorpan without the proposed hood

Floorpan without Hood

• benssson
• 27 Feb 2015
• 1

and here's what I'm proposing.

Floorpan with Hood

• benssson
• 27 Feb 2015
• 1

Hope those images make sense. Note the ducting number of turns/lengths/etc are quite from memory so they're not accurate.