The effectiveness of ducts largely depends on their intended use. In private homes in Norway, where ducts primarily serve airflow without additional heating, introducing heat can pose a problem. This is because it can lead to temperature differences that result in unwanted moisture, potentially causing damage to your home.

In private home settings in Norway, ventilation systems often feature inlets positioned high on the wall or in the roof. If warm air is introduced, it tends to circulate near the ceiling, failing to adequately warm the room or refresh the air. The system is designed to allow cooler air to enter, which naturally descends, while the warmer air rises and exits through the roof vents.

However, systems designed solely for ventilation and lacking heating capabilities typically have insufficient airflow. The ventilation fan isn’t powerful enough to adequately circulate and replace the air.

In contrast, commercial buildings are more likely to incorporate systems that combine both airflow and heating features for more comprehensive climate control.

I would be careful with adding heat from miners in the ventilation system. At least check your setup.