To understand more about the additional U Value please go to either Sliding Sash or Casement Windows and
produce a window with glass in your normal way. Then look to the U Value and click on Info.
The document that pops up will explain about the Calculated Value, the Model A value and the Model B value.
Sashes only types SOB, S0C and SOD will no longer show a U Value.
This has now been corrected.
This has now been corrected..