NOT True.... window glass will work for even 1000 w bulbs. As long as you have air going them single strength glass is fine. It's better to get double strength glass only for the fact that it takes a beating better then single does by far. Many times with single strength glass when you are changing out a burned out bulb and the glass is still warm it will break while you slide it in or out. The double strength glass is much thicker and stronger and just as easy to find.

But to answer your original question yes even single strength glass will work and you know the down side of it as well.