Case: The plaintiff (=pl) and the defendants (=def) are neighbors on the same floor of an apartment building. There was an area of air space in between their apartments that was used by both of them to extend their apartments. Def put a window in their extension’s wall, from which one can see into pl’s kitchen. They claim that pl gave them permission to do so, but pl denies it and began complaining during the window’s construction. Def conjecture that pl gave permission when she was not fully aware of its ramifications. They also point out that pl’s kitchen can also be seen from a window that existed from the original construction of the building. Def made the window non-transparent and is willing to make the window unable to be opened. However, pl says that having the window so close to her kitchen makes her uneasy, and that once a window exists, it is hard to stop it from being opened.

Ruling: [We saw last time that the situation comes under the category of hezek re’iya (damaging levels of invasion of privacy). Now we must look at the question of whether permission was given in a binding manner and/or what remedies need to be done.]
Poskim write at length about whether, to establish mechilla (relinquishing of rights) of protection from damages between neighbors, one needs three years of use without protest and the claim of explicit permission or whether a single usage without the owner’s protest suffices. We will only discuss particulars that relate to the issue at hand.
There is a machloket whether mechilla works regarding hezek re’iya. The Ramban says that the affront is so severe that mechilla does not work because the damaged person can later say: "I thought I could handle it, but it is worse than I imagined." Another reason that the mechilla might not work is that it is prohibited to look into another’s property. However, the Shulchan Aruch (Choshen Mishpat 154:7) rules that mechilla does work for hezek re’iya. On the other hand, the mechilla can only work when the mochel is aware of the extent of the damage (Ramban, Bava Batra 59; S’ma 153:3). The Netivot Hamishpat (153:3) adds that he must have experienced the matter several times without responding until beit din is convinced that he relinquished rights. Signing on building plans is certainly binding because people do so only after considering the matter carefully.
In our case, def admitted that they do not think that pl understood the significance of the planned window so that even if we accept their version that she did agree, it would be considered a mechila b’ta’ut (based on a mistake).
However, perhaps if the window is non-transparent, it should not be a problem. The Avkat Rochel (123) says that indeed such a window takes away the problem of hezek re’iya, and we do not have to be concerned that at some time in the future it will break. In general, possible future problems are not considered damage in the present. So too, as long as def make the window unable to be opened, they removed the damage, even if we can understand pl’s concern that the arrangement can be reversed.