How to terminate cooker hood ducting

Question

I have a probably stupid question about assembling ventilation pipe for a cooker hood.

I want to vent my cooker hood through the eaves rather than go through the roof as I suspect it's cheaper, less effort and less visually disruptive.

This is in a relatively modern extension of a circa 190 year old traditional stone and slate property.

I could core through the bricks, but I thought that was a more difficult job with the most scope for damage.

The hood has max flowrate at 386m^3/h so a bit of research suggests I can get away with 5"/125mm (or equivalent flat channel).

It's a tight squeeze, so I was thinking of using some flat channel to exit the eaves, which look like:

I was looking at the Manrose catalogue and I can't work out what I need to terminate the flat channel? Can you just cut a hole, use one of the grilles and place the flat channel up against it? Not sure how it connects - if indeed it does.

I know there are 'airbricks' that look like a 'connectable' thing, but I don't have much vertical leeway - just 6cm at the outside edge.

A am thinking of using a flexible or 45 degree flat channel connector at the left hand side is what I was thinking, just not sure if it has to go through an airbrick or can just poke into the 2cm wood of the eave (at number 9 above).

Hope that makes sense - I wish I had a selection of parts to 'play' with to see how these could fit together.

I have a toolstation, wickes, b&q and screwfix handy.

Thanks for any pointers!

Answer 1

Trouble is, the air is laden with moisture and will billow up around the outlet (whatever you use). This might cause staining, and even eventual rot.

Some of the roof tile vents are very neat and small these days (making assumptions here re. your tile type!) and run the pipe up to that? Best long term option.

Also, I'd try to run an insulated pipe (or surround the flat pipe with fiberglass) between the ceiling and the vent. Otherwise the hot air can condense on the sides of the cold pipe in the attic and run back.

If you must fit a plastic vent terminal, make sure it's well sealed to the eaves material to stop moisture laden air getting back into the attic (difficult if there are strip vents for the attic in the soffit or fascia board).

You could consider fitting the vent into a square of metal or plastic to protect the eaves material. I've used white perspex for this in the past.

Update In light of the better photos and your note about being willing to drill a hole. I'll amend my advice. Go for the core drill. It's always preferable to installing in the eaves or the roof for future maintenance reasons. Plus it's usually the shortest distance from the unit to the vent which is best.

Plus, a vent in a plastic pipe fitted through a solid wall is virtually maintenance free by comparison.

You're unlikely to run into a problem drilling a core hole through old brickwork. You'll need to hire a large special drill and corresponding core bit for best results. You can chain stitch a hole using a regular SDS drill bit and then chop out the core but this is likely to damage the wall and/or plasterwork internally.

Core drills form extremely neat holes. But you must have a stable platform to drill from. The drills are large and the large size of the core bit means you need to be able to hold the drill very securely as they can snatch a little, especially if you're not holding it properly.

Pick up your vent parts first, especially the plastic 'drain' pipe which will go through the wall. Core bits come in various close sizes; 100mm 115mm 127mm etc. etc.