In message , Huge
writes
On 2017-11-23, Clive Arthur wrote:
I need a grille on an exterior wall for a 150mm cooker hood extractor.

The choice is louvred, gravity or cowled.

Which is best?

IME, gravity. Otherwise you get a howling gale back through the hood when
it's switched off.

Hmm.. they also clatter on gusty days:-(



--
Tim Lamb