roof vent for kitchen exhaust
Hi, I'm installing a replacement kitchen exhaust (Neff - max 630m3/h) above my gas hob in a house. I have two questions:
(1) can I use PVC ducting or is galvanized steel recommended?
(2) Is there a specific roof vent that I need to purchase for this type of application in order to minimize any disruption to the air flow? Will a standard vent work or do I need a roof cowl? Right now, I have what looks to be a standard roof vent but I wonder if it's affecting the air flow and don't want to change it if I don't have to.
Many thanks in advance for any advice.