My house has two bathrooms and a kitchen all along one side of the house, each side by side. Each room has an exhaust vent, none of which are insulated. I live in Ontario which I believe (not sure by code) the ducting in the attic should be insulated on the outside.
FIRST VENT QUESTION (MAIN BATHROOM)
So I am preparing to insulate my main bathroom duct (in the middle of the spare bathroom and kitchen) because I believe this is required as there is a bathtub and shower in this room. I bought a Broan metal bathroom vent that says its for 3" and 4" round ducts. I just replaced it on my roof today as the current vent had no connection for round duct, however the 4" round duct I have fits extremely loose. See attached pictures.
How can I positively connect the duct to ensure no water leaks down into the attic? Is there anyway to get the duct in there tight? Maybe another fitting or attachment... I was potentially thinking of buying a 5" duct and putting an adapter 5" to 4" transition to connect to my fan as it would fit tighter.
SECOND VENT QUESTION (SPARE BATHROOM)
As much as I want to insulate the spare bathroom vent, its hard to get at, and there is only a toilet and sink in that room, so very little if any moisture is generated in that room. This is more used more for removing scents, and rarely.
If this is the case, does this vent need insulation?
THIRD VENT QUESTION (KITCHEN STOVE)
The kitchen vent is a 3-1/4 x 10 rectangular vent. Currently it was an immediate transition in the wall right to a 4" round duct. I read on the internet that when transitioning that you should keep the areas similar to reduce the pressure loss which can prevent issues. This means I would require approximately a 7" round duct. This size will not fit where the vent is located as its close to a rafter.
I don't plan on moving this vent as of right now so I was wondering if keeping the 4" round duct is okay? (The length to the vent is only about 2-3 feet at a maximum)