Q. Re- question 576 on reciting Kidush Levanah inside the house. Isn’t there another reason to avoid becoming tomeh if under a roof?

A. Indeed besides the reason quoted in the Mishna Berura (426: 21), that we are engaged in receiving the presence of the Shechina and it is customary to leave one’s home to welcome the presence of kings, Maharil quoted in Mogen Avrohom (426: 14) mentions that the reason not to recite Kidush Levono under a roof is to avoid tumah.

Poskim ponder if there is a practical difference between the reason presented by the Maharil and the one mentioned in the Mishna Berura. They suggest that the difference is whether one is allowed to recite Kidush Levono under a tree in the street. In such a case Tuma still applies since a tree is an ohel, but as far as going out to receive the Shechina, you did after all leave your home to receive the King (Yaskil Avdi 8: 38: 3, Simchas Olom 58)

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a