Kitchen extractor letting in cold air

Hi, I have discovered that our kitchen extractor hood is letting cold air into our kitchen. I found this out by measuring the temperature at the fan inlet.
What is the best solution for this problem? The outlet outside is a straight out pipe. I think it ought to be replaced with a gravity flap. The current outlet is cemented in and I am unsure about removing it without opening up the extractor.

I had this issue with a bathroom extract fan. I fixed it by getting a butterfly duct valve and fitting it just inside the wall.

The duct was flexi type so it was relatively easy to cut and re-fix.

in-line back draught shutter is effective and comes in metal and plastic versions. I fitted plastic version that gets a bit noisy on windy days

Mine is a metal one with springs holding the leaves in place. I’ve never noticed any noise from it. Being metal it is also cocooned in insulation.

Could you please provide an example of the valve? A link would be useful.

I bought mine 5 years ago and no longer have the details, so I searched online for “one way duct valve” and found this similar but plastic product.
100mm In-line Extractor Fan Vent Back Draught Shutter With One Spring…

Realising that the open shutters would interfere with airflow I bought one for a larger duct size and a pair of step down/step up cones to fit it in place.

Thanks for that. More specific searches for a manufacturer (manrose) got me to
The prices were about half of amazon plus delivery.

Manrose 1230 100mm in –Line back draught shutter ME1365973
The Manrose 1230 is a 100mm/ 4” circular in-line back draught shutter, which can be mounted onto the spigot of fans or in-line within the ducting. The 1230 can be installed to prevent cold air from being blown/drawn back into the room, reducing heat loss and energy consumption.
Power discount and

Klimapartner RKI 100 - 4 Inch Backdraught Shutter Insertable Vent with Rubber Seal
by Klimapartner

1 Like