Stove exhaust vent leaking cold air into house

I have a cooktop exhaust vent that is routed to the outside of the house. On the outside of the house there is a vent with a flat on it. Unfortunately the flat on the vent never closes - letting cold air in throughout the winter months.
Where do I find a replacement vent( I didn't see it at the home deopt)? Is this a job for a hvac guy?
TIA
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thats also why fart fans are such a bad idea
Mark
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dk wrote:

There are better vent caps that stay closed with exhaust is off.
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My Home Depot has several shapes and sizes, right by the bath fans. Most have spring loaded dampers built in.
If you don't feel confident doing this, an HVAC guy or skilled handyman should be able to do it for you.
JK
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dk wrote:

An HVAC guy will use a bit of toilet paper to gauge the extent of the problem, then you'll know what you're dealing with.
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FWIW, our Broan range vent has flappers on the onside over the stove and on the outside wall outlet. The outside flap assembly was in stock at Lowes where we bought it. A little hard for the clerk to find, until we gave him the part number from the installation instructions.
Joe
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