A "velomobile" is a cycle with a fairing, typically for weather protection; in many velomobiles, the fairing is also aerodynamic.
The Milan 4.2 and 1+ models are designed for carrying cargo, including a not-pedaling passenger. This gives a much larger inside volume than most velomobiles. The track is wider to allow reasonable cornering despite the longer wheelbase. Together this gives more frontal area and more skin drag than standard Milan models. But, the Milan 4.2 aerodynamics are still much better than most "cargo" velomobiles, and the weight penalty is estimated as around 5 kgs compared to a standard Milan model.
Although the Milan cargo models are not designed specifically as a housebike, Helge Herrmann (of Raderwork, which builds Milans) notes that one use of a cargo velomobile is as a motorhome -- that is, instead of bringing a tent, use the velomobile's weather protection both when riding and when stopped. A conventional velomobile is not long enough inside to lie down, but the Milan cargo models are long enough inside a person can plausibly lie down.