Oh yes, I can imagine that. And it will stay that way until May. Even when it is warm outside, it takes some time until the building heats up - needs at least 15C at night and 23C in the day. More and more of the recently built apartments are connected to district heating or gas lines, though.
The difference between Tunisia and Western Europe is: Europeans go in winter out for walks and get back home to warm up - Tunisians go out and sit in the sun to recover from the cold night, hehe (been there, done that...). If you got such an apartment, be sure to have a warming bottle with you and a functioning full bath with hot water ... you will need it, both.