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Having work done to my kitchen including having the fireplace opened up so i can put the cooker in there.
Just thinking about extraction above the hob. Will getting a standard flue liner dropped down through the remaining chimney work or should i install a hood on re-circulation and a charcoal filter?
Advice from anyone who's done this kind of conversion is appreciated
No, but just realised this is an option for us. Awaiting replies with interest!
I don't know the correct answer according to Building Regs etc. or the cooker manufacturers, but the extraction duct will inevitably require cleaning at some point. How frequently that is needed will depend upon the efficacy of any filters and the extent and type of cooking, e.g. steaming or boiling vs. frying, but even if it did not need it for some years, I would want it designed and installed to make cleaning (and also inspecting the duct to see if it needed cleaning) as easy as possible.
Just horizontally core drill a vent to the outside, will be a very short run so extraction will be very good. That's what I've done in the same situation.
I can't help thinking that the chimney might become damp as they aren't designed for relatively cold air which might be fatty/smelly, they are for very hot sooty air which will travel upwards very fast. Not an expert but that's my thinking.
Would there be any issue with fats/grease going up the chimney from the kitchen, which might build up over time and a naked flame from an open fire or wood-burning stove ?
You definitely want external extraction rather than recirculated. If you can go horizontally through the wall then that would be better.
The chimney doesn't sit on an external wall and I'm not sure next door would be happy with me if I vented into their kitchen. Going external horizontally isn't a goer unfortunately due to its position
The chimney won't have to deal with any fires though
If it's a two or three storey house, then I would try to avoid having a duct run the the full height of the chimney. At some point it will need to be cleaned, and you may find that extremely difficult/expensive. Unless they are very short, kitchen extract ducts are supposed to have access hatches in them which allow them to be inspected and cleaned, but I presume your planned install will not include making maybe three or more holes in the chimney masonry to allow such hatches to be installed.
I would also be concerned about the quality and specification of the ducting and the joins: it's not that unusual to see grease, oil and fat leaking through the joins of commercial kitchen ducting, even though you would expect it to be to a high specification.
In your shoes I would be investigating whether the top end recirculating systems would be acceptable (which I suspect will be very expensive German brands, given that they are the leaders in MHRV buildings, and recirculating systems will probably be used in their most energy efficient homes to reduce heat loss).
How about a downdraft extraction system instead? You could duct at low level to an external wall
Using flat mega duct against wall behind base units