Q. My sukka is indoors and it is covered by a number of horizontal windows that open each individually.
The size of the opening of each window is 55cm. by 2 meters (the beam structure separating the widows is 25cm.) Do I have to open at least two windows to have a shiur sukka, or is it enough with one?
A. There are different opinions as how large is the shiur of a tefach. Some Poskim maintain that a tefach is 11 cm. (Levushei Mordechai Y.D. 1: 152, quoting Chasam Sofer.) Many consider that a tefach is 10 cm. (Darkey Teshuvo Y.D. 53: 34, Beis Yisroel p. 156, T'nubois Boruch p. 42, Taharas Yom Tov - Brochos 22, et. al.). Igrois Moishe (O.H. 1: 136) opines that it is 9 cm. However, Shiurei Torah (3: 25) by Rav Chaim Noeh, Darkey Teshuvo (Y.D. 53: 34 ) and others, reckon that a tefach is 8.cm. While Chazon Ish is said to have regarded a tefach as being 10.16 cm. (Shiurin Shel Torah p. 3)
Horav Shlomo Miller's opinion is that the minimum size for a suka, held to be as seven by seven tefachim, means in the shape of a square, where each side is at least seven tefachim, not the total area as would be in a rectangle, similar to the window in your question. Therefore, the width of the window being only 55 cm. does not meet any of the above shiurin and you would have to open at least two windows. The Rov Shlit"a added that inside house sukos may have other issues in regards to the mechitzos, and should be inspected by a competent Rabbi.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a.
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