Most exhaust fans operate at about 50-60% of the manufacturer’s stated airflow. The manufacturers are not lying.

Convective looping happens when a difference in pressure is caused by a temperature change across a wall, with air constantly moving in a loop from hot to cold.

The top part of the window never sees the sunshine and therefore never supplies solar gain.

Why don’t we rely on windows for ventilation?

It’s a thing called ‘control’. Just as we have ‘control’ layers for our building envelope, we also want ‘controlled’ mechanical ventilation for our building.

…the photo reminded me of growing up on the farm and my father complaining about ‘highly educated do-gooders coming in and inventing new problems that don’t exist and making existing problems worse’.