Hi

I've got a rangehood with external inline motor and it has 200mm flexible wire ducting.

I am venting it out the eaves however the eaves cavity is very narrow.

I have a 320 x 95 approx rectangular gap the exhaust part of the ducting needs to pass through before reaching the vent in the eaves.

I can't actually reach the gap physically (this is with me lying down on boards inside the attic and reaching my arms out as far as they go)

My thought was to bend about a 1m length of 250 mm ducting into a rectangular 305 x 90 shape pass it through the narrow area and then pull it out a 250mm hole in the soffit and attach a 250mm round vent. 

I thought it was better to upsize to 250mm for the squeeze as the 200mm will loose a lot of cross sectional area when you change it to a rectange. (Area of 305 x 90 = 270 cm2 which is not too far of the 200mm round diameter area of 315 cm2).

My question is:

- What kind of exit vent is best for an eave?

- What direction should the louvres face? (ie do they point towards or away from the house)

- Am I likely to need a damper valve to stop air going the wrong way (I live in a windy area), I could always retrofit this later on.  Normally with a wall facing grill the little louvres can fall down with gravity to prevent the wind going through, but I'm not sure if such a setup exists for an upside grill on the soffit / eaves.

- Where is the best place to buy vents at public prices? I'd need 1m of 250mm vent , a 250 to 200 reducer and the 250 mm external vent cover with fascia.