Replies

1. 
   geob21 | Sep 24, 2002 03:00am | #1

   First - I wouldn't point and putty in insulated units.

   That said there are other things to check. The size of the insulated units dictates their thickness and will varie along with the glass thickness. This is confusing  I'll try to explain. If you have a large piece but can only have 1/2" thickness using 1/8" glass may result in the panes touching in the middle giving a beautiful rainbow effect.

   Take the sizes to a couple of local glass shops and see what they suggest.

   Also make sure the frames and operators will be able to handle the added weight.

2. 
   IronHelix | Sep 24, 2002 02:11pm | #2

   I've had experience in retro-fitting IG panels to existing single glaze sash.........casement, awning, picture and double hung. 

   The router cut can be tricky due to the depth of the glazing rabbet from the top of the sash rail. The length of the shaft on the bit is often too short, or when extended to make the cutter the off center oscillations cause the bit to fly out of a 1/4"collet. Lastly the control of the router is difficult when perched on the top edge of a casements narrower rail.  Careful planning and added jigs and supports are often required, which is worthwhile if doing several windows..............but for only one or two the cost usually drives the customer to other options.

   If you surmount the routing problem, clean the corners to square with a sharp chisel.  The glazing channel should be a minimum of 1/4" deeper than the thickness of the IG that you have ordered.  When ordering  IG you may spec the thickness from about 7/16"  and on up!  The thickness of each sheet of glass used to make the IG is controlled by the manufactured and is determined by the size ( length x width) as to when the single strength sheet is replaced by double strength (1/8") or greater for picture window applications.

   When you install the IG panel in the routed sash use the sealant/glazing material specified by the IG panel manufacturer in order to avoid the glazing material from degrading the edge sealant of the IG.  Larger IG panels will require glazing cushions and mechanical keepers, as the glazing sealant in itself may not have enough strength to hold the IG in position. 

   An exterior wood trim for glazing is an option and will often cover the metal IG divider bar and sealant edge that is visible from the outside, or a wide bead of colored glazing material will also cover.  When installing wood glazing trim be aware of trapping water between the glass and the trim, thus leading to rot in the frame.

   There are lots of "ifs" and "buts" to this question you have posed..........specifics are available as encountered.     As always "CP" is the final say.

   Good Luck..............................Iron Helix

   ps..............CP is "Carpenter's Prerogative"

1. 
   Pilarone | Sep 24, 2002 04:37pm | #3

   Iron Helix,

   Thanks for the tips!