Undersize replacement IGU's? Do or Don't?
New to the board and want to thank everyone for their advice in advance.
I am replacing 18 IG's in my 10 yr old Simonton Dimension One PVC clad Casement and picture windows.
All IG's are 3/4" and all are inside mount with pvc stops.
Spoke to a Simonton tech and they suggested undersizing the replacement IG's 1/8" on the width(leaving 1/16" on the left and right) and 1/16" on the height due to their tight mfg tolerances and that the frames sashs are 10 yrs old.
Rep said better to be slightly "too small" (1/16") than too large due to over shimming and PVC expansion.
My glazier is not worried about the casements but said the picture windows(transoms that are 18.5H x 66"W may be a problem if the original installer over shimmed.
Long to short....which is more dangerous? Going with original mfg IG sizing or baking off am 1/8" on the width and 1/16" on the height?
BTW the replacement IG's are direct from Cardinal IG...3.1mm Low E 366/Argon/XL Edge Spacer......
Any opinions greatly appreciated as I have to order the IG's tomorrow