Why do riads feel humid, especially at night?
The short answer
The courtyard fountain that cools the riad during the day keeps running at night. Thick walls absorb and release moisture. Limited air exchange traps humidity in ground-floor rooms after dark.
The courtyard fountain runs continuously, adding moisture to the air. The orange trees transpire. The earth walls — pisé and tadelakt — absorb moisture during hot dry daytime hours and release it at night when temperatures drop and relative humidity climbs.
Thick walls and small openings mean limited air exchange. The courtyard that functions as a cooling chimney during the day becomes a moisture trap at night, when the convection loop weakens and humid air settles into ground-floor rooms.
Riad architecture trades humidity management for temperature management. Modern riads with mechanical ventilation handle both. Older ones make you choose.