Offset units, also referred to as step-glazed units, have the edge of one glass ply extend beyond the edge of the other glass ply on one or more sides of the glass unit. Offset units may be specified for functional or aesthetic reasons. Examples include corner conditions or operable windows. Offset laminated glass units are not available.
Types of Offset Insulating Units
Offset units are defined by the number of offset edges and which ply is offset. Viracon can provide offset insulating units with 1, 2 or 3 edges offset. For the offset, the exterior ply must be larger than the interior ply. This is referred to as an exterior offset.
Viracon does not fabricate staggered insulating units where both glass plies are the same size and assembled so they are offset from one another.
Designs incorporating offset insulating units can be complex so the following items must be considered.
- Quotes: To ensure the offset units can be manufactured by Viracon for a given application, all requests must be reviewed and approved prior to receiving a quote.
- Offset Distance: The standard offset distance is less than or equal to 3/4” (19 mm). Offsets greater than 3” are not available.
- Heat Treatment: All glass plies must be heat strengthened (HS) or fully tempered (FT) in an offset insulating unit. It is recommended that all fully tempered glass also be heat soaked.
- Edge Deletion: The deletion will be continuous from the offset glass edge to the spacer with 95% of the coating removed.
- Sightline: An increased sightline may be required for offset insulating units due to shear load on secondary sealant from the outboard glass ply dead load. Viracon will calculate the sightline for all offsets.
Silicone Fill Options
The secondary seal in Viracon’s insulating units is silicone. There are three fill options available for offset insulating units.
- Normal Fill: The silicone edge may vary and have a rounded appearance at the corners.
- Buttered Fill: A silicone layer is applied to the surface of the offset lite.
- 90° Fill: A custom fill where the offset lite is masked to achieve a uniform silicone edge. All requests for 90° fill offsets must be reviewed and approved prior to receiving a quote.