Question: I slept in a sukka as a teenager though now that I’m married with children, I am reluctant to leave them alone at night. Is that a good enough excuse to sleep in the house?
Answer: The Shulchan Aruch (OC 639:2) writes that while one is allowed to eat a snack outside of a sukka, the halachos of sleeping are stricter, and one shouldn’t even take a short nap outside of a sukka.
Nonetheless, the Rema justifies the practice of many who don’t sleep in their sukka. Firstly, he reasons, the sukka may be too cold to sleep in. One who is particularly uncomfortable (mitztaer) is exempt from sleeping in a sukka. The Mordechai (Sukka 741) wrote that in his time (13th Century, Germany) most people didn’t sleep in the sukka due to the cold weather. The Mishna Berura (639:17), however, understands this to refer to someone who doesn’t have pillows and blankets to keep them warm. Seemingly, one who does have would not be exempt from sleeping there.
Additionally, the Rema writes that if one’s wife can’t sleep together with him in the sukka, he is exempt. The Taz (OC 639:9) and Shulchan Aruch Harav (OC 639:9) explain that as sleeping alone can ruin one’s simchas Yom Tov, it would be better not to sleep in the sukka (See Mishna Berura 639:18).
The Rema (OC 660:4) cautions against building a sukka that is unfit to live in, due to it not being safe or comfortable, writing that such a sukka wouldn’t be kosher. The Mishna Berura (640:18) points out that if it’s just the climate that makes it difficult, though the sukka is otherwise sound, it is kosher as one could take extra blankets in and sleep there comfortably.
Rabbeinu Manoach (Sefer Hamenucha, Sukka 3:6) writes that even those who don’t sleep in the sukka at night, should try to do so when napping during the day, especially as many of the above reasons aren’t relevant.
In conclusion, the acharonim allow one to sleep outside of the sukka if one is concerned about leaving their family, though one should try, where possible, to take naps in one’s sukka.