High temperature stir frying and deep frying is minimally greasy, if
you use a good high temperature oil. However, when you add the food
ingredients to a stir fry there will be some rapid boiling in oil and
that causes steam with some oil carried along with it. At least it
is not burned oil.

Maximum grease load results from grilling (we do that outdoors) and the
European technique of searing a hunk of meat before pot roasting. Oh,
and any paste fried in oil; that generates a lot of oily steam and it
is a key technique in some Indian and Mexican dishes.

JoeSpareBedroom wrote:
Can you imagine lying on your back in your crawlspace, trying to disassemble
and clean filthy, greasy ducts?

Yes. And I would much rather do it under the house than under the roof!

I used to live in a house with a downdraft cooktop (oven was on a wall)
and it was only fairly effective. Certainly better than an underpowered
recirculating hood. But we have a standard range: cooktop over oven.
Short of a total remodel of the kitchen, the range will have to stay
where it is, on an inside wall. On the whole, I am favoring a straight
vertical vent through the roof, with a high-power "Chinese" style fan.
Can I get a closing cap? Or would the fan be strong enough to lift a
hinged cap without too much compromise of the exhaust? How drafty are
these through-the-roof vents?

To vent a hood down, I would have to open the wall cavity, and maybe
also build a box out from the wall, so the range would protrude out of
the counter by a few inches. And the outlet would be at knee height
right beside our entrance.

Good brainstorming here!

Una