Insulation of vapor extractor (chimney effect) with wool?

Hello, we had exactly the same problem back then (15 years ago). We also installed a check valve in the pipe. This has actually solved the problem effectively to this day. Best regards, Steffi.

Hello, we had exactly the same problem back then (15 years ago). We also installed a check valve in the pipe. This has actually effectively solved the problem to this day. Best regards, Steffi.

Thank you, we will do the same accordingly!

You write that you have a ventilation system. If the two fans do not run synchronously, it is possible that the air has chosen the path of least resistance.

Hello,

I would install the check valve as high up as possible. Otherwise, you have a relatively long "cold" pipe in your house.

Regards,

Alex

Update: Non-return valve has been installed. Problem actually solved. I installed the valve directly on the ceiling of the 1st floor; the pipe is insulated upwards.