I live in Fez medina in a traditional house. It is old, maybe 300 or so years old, give or take based on the history of the neighborhood. My house is a single family house that belonged to a merchant. He may have been a grocer but I am not really sure and the house was in the same family for at least 100 years, but probably longer. My house isn't a riad, it's probably not even a dar, it's most likely a dwira. It's a cool house and I feel very fortunate to live in it.
A riad has an interior garden and is quite large. Some riads were constructed solely for social functions and others had multiple families living in them. I have seen some with the garden area outside in an area surrounded by the house proper and others where the garden is in a central courtyard within the house, usually with a fountain in the center of all. A dar is a courtyard house without a garden and again, multiple families shared it and the space is quite large and the roof is open. The multiple families might have been various wives of a single man, or brothers sharing a family house or other dependent family members living in a house owned by a single resident family. A dwira is a small house, sometimes for servants, and sometimes for one family only. It is built on the same principle as the big houses with the salons and courtyards and open roof, but small.
A lot of tourists comment on their experiences in the traditional houses because they are not at all like the Western or modern style houses most people live in today. The first thing you need to know about a courtyard house is that all the rooms and most windows open into the center of the house. There are some windows to the outside, but when you are thinking about medieval, fortified cities, big windows were not popular options. Muslim culture is centrally focused, too, into the heart of the family and the home is private space. In other words, you aren't showing off your goods in a picture window on the front of your house. It can feel a bit strange at first walking into a house that may feel closed off.
Another feature of a traditional house is lack of privacy. Since most rooms and windows open onto the courtyard, you can hear and see most of everything happening in all areas of the house. Even some of the very large houses have very little privacy. Acoustics are strange too. Sometimes rooms can be on opposite corners of the house, yet you can hear every word back and forth. In a collective culture where the family spends a great deal of time together and guests may be coming and going or staying for long periods, it is the perfect house. I often said I wish I had known about these houses when my children were small. If you haven't experienced this, it's a good way to get a feel for what it's like to be in Moroccan family. Other guests in the house might not be your friends or family, but you are living together and sharing a lot!
The old houses can be dark and there is no really effective way to heat them, although many places are installing AC units in the walls, and some times people complain they are damp. I read somewhere that French colonialists thought the medina was unhealthy and that was one of the reasons they remained in the new cities outside. The construction of a traditional house is usually limestone and sand bricks and wood beams. The house should breathe and adapt to the climate - cool in summer, warm in winter. Some of the repairs and additions done in recent times involve cement and other modern building materials that don't work the same way or upset the natural balance. Other things, like modern plumbing installations, also affect the house. For the most part, a well-built and maintained house that is properly ventilated should be comfortable most of the time.
Another interesting feature of medina houses is their interconnectedness. Every house shares a wall with another or even several others. Sometimes the floors of one house enter between floors of another house. You can stand up on the roof and look down into the maze of rooftops and satellite dishes and be hard-pressed to figure out where the streets are. There is a big house behind mine and I still don't know what street it is on or how to get there from my house.
So if you haven't experienced a traditional house yet, try it. I love the open roof concept and can't imagine being without now. Just wait until you see a full moon shining into the courtyard at night, sparkling on the fountain and bathing everything in a silver glow. That alone is worth it!