Why were medieval kitchens in the courtyard?

Answer 1

The chimney was invented in the 12th century, and because chimneys were expensive, few buildings of the later middle ages had them. The way smoke was vented from fires used to heat buildings was to allow it to escape through holes in the roof or under the gables. So most cooking was done outside unless the weather was bad. In castles and monasteries, there was usually a separate building with very large open windows for cooking in bad weather, and the courtyard was a logical place for both cooking outside and the kitchen.