Q. We were short one for a minyan in our backyard. Since one neighbor was sick in bed, he approached the window were we could see him. If the widow is open, but it has a screen (for insect protection), could we count him for the minyan?
A. Shulchan Aruch (O.H. 55: 14) rules that one standing on the back-outside of a shul, and there is a window between them, even if it is several floors high and even if it is not wide four, and shows his face to them from there, he can be counted with them to the minyan of ten. Mishna Berura (52) maintains that on the onset one should try if possible to join completely the minyan. Kaf Hachaim (ibid. 76). asserts that a glass window is considered a mechitza or interposition, since it can so be used to separate from unclean materials, others disagree (Kol Hatorah p. 241).
Horav Shlomo Miller’s Shlit’a opinion is that even if the window is closed as long as the ailing neighbor can be seen through the glass, he can be part of the minyan for reciting kaddish and a short amida as quoted on question 2638. namely: “Since in halacha a minyan of people on adjoining porches is unclear, one should not daven Chazaras Ha’shatz or kriyas Hatorah since it is a safek bracha l’vatalah. Therefore, this minyan should only be formed at mincha, with a short Shmonei Esrei in order to say kaddish and Kedusha.
One should also be careful that either everyone should see the Chazan, or the Chazan should be able to see everyone. 
On question 2655 we mentioned that the Rov added permission to daven maariv also.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a.