ᐅ Insulating a Kitchen Exhaust (Chimney Effect) with Mineral Wool?

Hello, I would like to ask for a brief collection of ideas regarding the following issue:

We had a ducted exhaust hood installed, which vents the air through the roof. The kitchen is now installed, and it appears more and more that a chimney effect is occurring, meaning that cold outside air is entering the living space as if through an open window.

There are supposedly check valves, but the duct can only be accessed by removing the hood (which is difficult).

I had the idea of inserting insulation material (wool). This is technically possible. Is this feasible, or can anyone advise against it?

Any other ideas?

Maybe take a look at the Berbel wall box sometime? Adding insulation inside the duct seems counterproductive to me... you might as well switch from exhaust air to recirculated air directly.

The air outlet is located on the roof, so there is no wall vent box present.

Cut open the pipe in the attic and install a non-return valve if one is not already present. Under no circumstances should insulation be placed inside the pipe, as this would prevent the extractor hood from functioning properly.

You write that there are supposedly check valves, so you are not exactly sure? Maybe take a look, even though it’s not very pleasant to do.

As a rule, warm air should rise and escape upwards, not cold air coming inside. Do you have negative pressure in the apartment?

Does the cold air only come in when it’s windy? What does the pipe look like at the top, is there something like a windbreak or similar?

Hello Garfunkel,

There is currently no backdraft damper installed. I meant that such dampers are available on the market. A wind barrier is installed on the roof, so wind itself is not the issue. It is rather a constant, cold airflow coming downward. Negative pressure inside the living space is quite possible due to the ventilation systems.

I think we have no choice but to remove the exhaust hood and install a damper.