i do not know much about any thing outher than the glass, glass frame
bar's, butal, spacers in the channel but here are some things i can
tell you about (renual by anderson and anderson) their windows are
supplyed from cardnil plants and i know cardnil warrenty's the butal
on their windows to not break a seal for 20 years if you dont konw
what that mean's i will define it.


There is butal on the window fram to hold the glass on and seal the
gasses inside that make them more efficant. their is menny different
kinds of coatings for the glass and different tempors and the real
expensive glass, Laminated glass (2 or 3 peaces of glass abrazed
togather) outher wise knows and safty glass.