Wireless broadband was always marginal here (at least one
mile from the tower, with trees in the line of sight ) and became
impossible the day the windows were replaced with modern
"Energy Star" units, double-pane sealed units filled with gas
(either argon or krypton, I forget which.) I could not be sure of
the cause, but managed to reach an ISP engineer. One of his
suggestions was to try the directional wireless modem at an open
window, i.e. no glass -- which immediately provided a satisfactory
signal. I have instructions for various tests thus will quantify the
difference if I can.
The engineer said he had never heard of either window structure
(aluminum here with steel magnets that hold the fly screens in place)
or gas-filled sealed panes obstructing wireless signals. Has anyone else?