The Best Window, Part Deux

Ok I remembered a couple things missing from part one...two other important aspects that are related to the subject of the glass package.  One is the glazing bead. This is the finishing touch the factory puts around the perimeter of the glass that does several things 1) it "hides" the edges of the glass as it rests on setting blocks so it does not sit in water in wet conditions 2) it form fits to keep dirt, dust, etc. from accumulating, and 3) it gives slight pressure against the glass.  Some glazing beads are merely plastic and not the same quality as the vinyl.  I've seen these turn chalky, cup and bow, and disintegrate after a few years.  The best kind is called a dual durometer glazing bead which is made of two materials, vinyl (the same quality as the window) and rubber which acts as a seal against the glass.  This does a really good job of keeping dirt out from between the glass and the bead.  I can't tell you how bad it looks from the inside looking out when a lot of dirt gets in there.  Plus you can't get in there to clean it out without removing the bead which is impossible for the average homeowner to do.  

The second thing I need to mention is the structural metal reinforcement inside the vinyl in the meeting rail.  Always look to see a cutaway of the meeting rail.  All reputable manufacturers have this sample along with a "corner cut" of the main frame, usually in some type of demo kit.  The reinforcement varies greatly amongst manufacturers.  Some use very little, and some use a lot.  Some use glavanized steel, but the best is aluminum reinforcement due to it being lightweight, strong, and it does not rust.  The metal reinforcement is the main structual member of a window and on a single hung it literally supports the weight of the glass.  Plus look to see if the screws of the cam locks screw into this metal, not just into vinyl.  I've seen a few that do not and therefore are not very secure.

In a double pane window, the sealed insulated glass unit, or SIG, is where the rubber meets the road.  It is eighty percent of the window, you have to look though it, and it needs to be thermally efficient.  Luckily for you the technology of the SIG is significantly better now than, say 15 years ago, when you'd be lucky to get 12 years before there would be a seal failure.  You've seen or heard of this before as it is called moisture or "condensation between the glass".  I went to a house once that had it so bad it looked like shower door glass!  That's why the Seal is very important of a Sealed Insulated Glass Unit.  Caps on purpose. Sorry.  Anyway I could give you a history lesson of the evolution of spacer systems but instead I'll just recommend the best spacer to look for...Superspacer by Edgetech.  Google it, make sure the window you are looking at has it, and get it.  The best spacer system out there for a variety of reasons.    

The airspace, or gap between the panes, has varied over the years.  At one time it was only 1/4" or so.  Then they went big, like over 1 1/8" overall.  The P. G. & E utility/monopoly did a study once showing a parabolic that peaked right at a 1/2" airspace. In this publication they still recommend this. Today most manufacturers offer exactly that.  I do recommend argon gas fill too, especially combined with superspacer, as it has a very low U-factor.  In addition it is quieter and lasts a long time (100 years in testing).  If a salesman says the argon leaks out he's telling the truth...if its not superspacer!  

Lastly, glass thickness itself varies.  Most common is single strength (about 1/16"), then double strength (1/8"), and even triple (3/16") and 1/4" thicknesses.  A good SIG package, in my "expert opinion", would be double strength glass, with a half inch argon-filled airspace sealed with superspacer.  

Look for a heady discussion next time regarding...wait for it....spectrally selective low emissivity glass.  What fun ;)