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Building regs and kitchen extraction

(16 Posts)
Pigleychez Thu 08-Sep-16 22:20:37

Starting a new kitchen extension soon and started planning the new kitchen today. Been looking at options for cooker hoods ( downdraft, pendant etc) and reading about the requirements from Building regs.

The Issue we have is that the hob is planned to be on the island and its looking like the island will be just under where the roof is valuted from the extension so a ceiling or traditional hood isnt going to be possible.

Just wondering what others have one for ventilation in thier extensions?

OnePlanOnHouzz Fri 09-Sep-16 17:45:39

If you have a vaulted ceiling then it sounds like a possibility of putting the entire kitchen on a raised step -so giving you a void to put the duct out of.

PigletJohn Fri 09-Sep-16 18:32:57

If you don't have an extracting cooker hood, you can use an extractor fan. But it must be more powerful because of course it is not extracting the steam and fumes at source. The power (cubic metres per hour) required is calculated according the size of the room. So open-plan will need a very powerful one.

Consider if you can use a ceiling hood and a duct. Examples.
Elica make a good range, but their website is awful, so ask them to send you their glossy brochure.

Powerful fans are of large diameter, they can turn relatively slowly and be quieter than small fans.

there is a guide to fan power calculator here

PigletJohn Fri 09-Sep-16 18:36:43


if it is not built yet, perhaps you could put a duct in the space between the ceiling and the room.

PigletJohn Fri 09-Sep-16 18:37:03

ceiling and the roof

Shurelyshomemistake Fri 09-Sep-16 20:07:47

Or downdraft and duct under floor?

Depending on space and how much cookinv you do ... i'd be tempted to do whatever was cheapest/ least unsightly to get it past BR. We barely use ours and I wish wd could'vd saved £1000 and not bothered!

Pigleychez Fri 09-Sep-16 20:24:13

Extension is due to start in March. Gussing we will need to contact the builders to see about the different possibilites.

Shurely- We too barely use ours.. The back door is always open for the dog anyway!

Piglet- Anything on the ceiling is an issue as its a vaulted roof with skylights.

Im guessing a fan on the outside wall will be easiest. Can you get nice looking fans??

PigletJohn Fri 09-Sep-16 21:32:18

You could vent it through the roof like a chimney, but get the roofer to do it. Anyons else making holes in a roof may cause leaks.

If you go for a wall fan it might well be a 12-inch.

Try the calculator tool and it will suggest a few suitable ones.

Pradaqueen Sat 10-Sep-16 16:12:57

Retractable worktop mounted extractor? Expensive but might solve the issue?

PigletJohn Sat 10-Sep-16 17:15:38

best way is to capture it above the hob. If you can't do that, the steam and cooking fumes will tend to rise towards the ceiling, so the high extractor will be more efficient at capturing and expelling them.

If you have a large wall fan it need not be obtrusive, especially when it is above the height of your wall cabinets.

Kharvey12 Thu 01-Dec-16 21:57:53

i am also just getting a kitchen extension done, thing is that the room is quite large open plan (8m wide, 7m deep for the entire open plan area) so how do they classify exactly what space you need for the extractor hood/fan to clear? Is it the whole thing or do they take a subset of the room?

I think i might be a bit stuffed to get something with the right capacity. Big velux over where the hob will be and UFH already gone in under screed so cant duct under the floor or upwards... eeek. Looked at the calculator PigletJohn posted and it said no fan existed that could do the job (537l/sec)...

I think we are stuck with a recirculating downdraft extractor, I know they are not widely advised due to not actually extracting smells etc but we do have 4 lovely big opening velux windows in the roof to let all that out... HOw do we pass building regs? I had no idea it was even part of building regs until today and now having a panic.


namechangedtoday15 Thu 01-Dec-16 22:15:49

We've just had a large extension. We have an extractor fan on an outside wall. We have a bank of tall units (not quite to the ceiling) and then it drops down to base units where the hob is. We have the extractor fan above the tall bank of units (on the wall rather than the ceiling). It is relatively effective but we hardly use it, we have a window on the other side of the hob and just open that.

It passed building regs anyway.

bojorojo Thu 01-Dec-16 23:14:56

I have a kitchen in a large glass orangery and the house is open plan. The only solution that is likely to work with an island hob, and I have one, is the extractor to be mounted in the island which rises up when you want to use it. You have to design the island to accommodate it because it sinks into a void. Any other solution is plumb ugly. Vent out under the floor. I have opening roof lights and large external doors.

Having said that, an extractor in a large space is just not needed. We actually don't have one. No problems in 5 years of use. Building inspector just asked where it was going and never came back to check. It was in the design and the wiring plan. We just didn't buy it. The kitchen is part of an area that is about 18m X 10m.

Kharvey12 Fri 02-Dec-16 16:21:06

it's an island hob with no wall to duct along sad

johnd2 Sun 04-Dec-16 14:19:04

>500l/s is crazy, that would clear all the air out of an average 3 bed house in a few minutes! Even 100l/s I'd have thought would be plenty.

Tatey25 Sun 11-Dec-16 10:03:00

As Piglet John says, you could use an extractor fan. You probably need at least 12 air changes/hr. to calculate the fan Ventilation rate (l/s) = air-change rate (12) × room volume (m3) × 1000 (l/m3)/3600 (s/hr)

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