Extractor fan ducting

pledgeX

Can anyone recommend a reasonable ducting kit for a cooker hood extractor fan? The majority of reviews I've seen are not positive.

The hood itself recommends 150mm, or 125mm diameter at a minimum. I'd rather use the 150mm option to ensure best performance.

Most of the 150mm kits I've seen actually use a pipe that require a 160/170mm hole though. Due to the route it needs to take this extra couple of centimeters could be problematic.

The ducting route itself is nice and short. Either 300mm, or 600mm total length of ducting, depending on which route we take.

retepetsir

Any chance of using adapters to convert over to the rectangular style? I found this easier to run above cupboards, etc.

Like this - http://www.screwfix.com/p/manrose-rectangular-flat-channel-white-100mm/14118

Jonesya

Have a look at Megaduct 220 - it's a large capacity rectangular ductwork so you can go from 150mm circular, up into rectangular that's easier to box in. For the wall outlet, you can use a double air-brick, rather than a circular cutout. If you get a kit, consider a back-draft damper.

You might get away, depending on the hood and air flow, with the smaller rectangular ductwork Supertube 125.

Available from various suppliers, these were reasonably priced when I bought some several years back:

Megaduct kit:
https://www.bes.co.uk/products/181a.asp

Individual duct parts with the dimension info:
https://www.bes.co.uk/products/180.asp

thescouselander

I had exactly the same issue with our cooker hood as I couldn't find a way to drill a big enough hole through the brickwork of the house. In the end I went with standard 120mm circular ducting but I used the solid rather than the flexible sort to help with airflow.

It all works fine and installation was a lot easier than going for the 150 mm pipe.

pledgeX

Thanks for the advice folks.

I picked up a 150mm rectangular kit from Wickes so I could take a closer look at it. The plate that sits on the outside of the house looks like this:



This looks like it'll be a lot easier to fit than a 150mm circular kit but I've got a couple of questions:

1) It's exactly the same size as a brick, which sounds good in theory as I can just remove a brick and replace it with this. However, the external fascia only has a 1cm 'rim' around it so if I were to screw through this to attach it to the wall, it'd go into the mortar which isn't going to hold. How would I fix it to the wall?

2) There's no back draft damping so the air can just blow in from the outside. Most of the back draft stuff I've seen is for the circular vents. Also a lot of the back draft kits I've seen involve flaps which people have complained about being loud and flapping in the wind. The vents in the air brick angle downwards and the neighbours connecting wall is only a 2m away so it's unlikely that the wind will blow directly into it. Would you still recommend a back draft kit?

flashg67

I've never bothered with back draft damping but the couple I've fitted haven't been particularly exposed. What about looking for a suitably sized cowl which will give some protection, but not restrict the flow?

albert_s

125mm round will have better airflow than 150mm rectangular,
if you can, use round, even go a size down,
use solid wall rather than flexible, if you need to use flexible use metal rather than plastic, and use insulated if you have the space,
keep bends to a minimum, remember, 2x45 bends are better than 1x90, even if the 2x45s are right next to each other,
an outlet the size of one airbrick is nowhere near enough surface area for a 125mm round, never mind a 150mm duct, even a rectangular one,

wrightk

pledgeX wrote: »

Thanks for the advice folks.

I picked up a 150mm rectangular kit from Wickes so I could take a closer look at it. The plate that sits on the outside of the house looks like this:



This looks like it'll be a lot easier to fit than a 150mm circular kit but I've got a couple of questions:

1) It's exactly the same size as a brick, which sounds good in theory as I can just remove a brick and replace it with this. However, the external fascia only has a 1cm 'rim' around it so if I were to screw through this to attach it to the wall, it'd go into the mortar which isn't going to hold. How would I fix it to the wall?

2) There's no back draft damping so the air can just blow in from the outside. Most of the back draft stuff I've seen is for the circular vents. Also a lot of the back draft kits I've seen involve flaps which people have complained about being loud and flapping in the wind. The vents in the air brick angle downwards and the neighbours connecting wall is only a 2m away so it's unlikely that the wind will blow directly into it. Would you still recommend a back draft kit?

I would definately recommend NOT buying a backdraft kit. If it is the flap type, they are useless. The inline (in duct) ones are slightly better but that involves buying the whole kit to essentially just buy a piece of plastic that sits inside the tube (which you cannot buy on their own)

I would also consider your options more carefully. As others have suggested a round duct will be better and you will have far more options with regards to grills internal and external. Even if you have to borrow or hire a core drill for the day. Round rigid ducting costs about £2, then you simply insert this through your nicely core'd hole,attach the grills internal and external to the tubing (just slots in) and the grills then attach to surrounding wall