Island Kitchen hood duct

[xavb]

Hi,

We're installing an island kitchen hood, and have a few questions on the ducting:
I hear its recommended to Not use flexible ducting, but a smooth duct. - Does it make a big difference to the airflow?

The duct goes as follows: 1. straight up 2. right angle 3. right angle again. 4. chimney. - Between 3 and 4. the duct 'goes back down' a bit into the chimney, because its 5 cm lower= is this a big hinder on airflow?

cheers,
xav

 

[Alarm]

Think about it, each bend detracts. Then it has to go up a chimney?
How long is the run?
You might need a jet engine for a decent air volume removal

 

[xavb]

its pretty long :S
straight up: 1 to 2 = 40cm
90 bend: 2 to 3 = 25cm
90 bend: 3 to 4 = 110cm

it has to be this way, hence i've been emphasizing on using smooth ducts to the kitchen dude.
plus he's doing it in a way that from 3 to 4 its slopes back down 5cm to the chimney hole in the wall.

i'm no pro which is why a kitchen dude's doing it. but i'm wondering if these 2 factors 1. smooth duct instead of flexi. and 2. that it shouldn't slope back down. make much difference or whether i'm just being compulsive?

cheers,
Xav

 

[xavb]

its pretty long :S
straight up: 1 to 2 = 40cm
90 bend: 2 to 3 = 25cm
90 bend: 3 to 4 = 110cm

it has to be this way, hence i've been emphasizing on using smooth ducts to the kitchen dude.
plus he's doing it in a way that from 3 to 4 its slopes back down 5cm to the chimney hole in the wall.

i'm no pro which is why a kitchen dude's doing it. but i'm wondering if these 2 factors 1. smooth duct instead of flexi. and 2. that it shouldn't slope back down. make much difference or whether i'm just being compulsive?

cheers,
Xav