Warm-edge spacer (IGU)
Warm-edge spacer is the low-conductivity bar at the perimeter of an IGU, replacing older aluminium spacers. Eliminates cold-edge bridge and perimeter condensation.
Ask Chalkline about this →A warm-edge spacer is the low-conductivity perimeter bar inside an insulated glass unit (IGU) that separates and seals the two (or three, for triple-glazing) panes of glass. It replaces the older aluminium spacer that for decades was the IGU industry default. Aluminium is highly conductive; an aluminium spacer creates a thermal bridge around the edge of the IGU, causing the perimeter centimetre or two of the inner glass surface to run noticeably colder than the centre of the pane. The cold edge causes perimeter condensation on the inside of the window in winter (the classic 1-inch-wide misting band around each glass pane), wastes heat, and degrades the unit’s overall thermal performance.
Warm-edge spacers solve this by using a much less conductive material for the spacer:
| Spacer type | Material | Thermal conductivity (typical) | Performance penalty |
|---|---|---|---|
| Aluminium spacer (legacy) | Extruded aluminium | High (~205 W/m·K) | Cold-edge bridge, perimeter condensation |
| Stainless steel | Thin stainless | Moderate (~16 W/m·K) | Modest improvement |
| Polymer “TGI” | Plastic with metal foil vapour barrier | Low (~0.3 W/m·K) | Strong warm-edge performance |
| Silicone foam (“Super Spacer”) | Silicone with structural reinforcement | Very low (~0.14 W/m·K) | Best warm-edge performance |
Key brand examples on Australian residential:
- Edgetech Super Spacer: silicone foam, premium warm-edge.
- Technoform TGI: polymer/foil hybrid, common on mid-range.
- Cardinal X-Y: composite spacer for triple glazing.
Performance impact:
- A warm-edge spacer typically reduces the IGU’s edge-condensation susceptibility by 30 to 60% (i.e. the perimeter glass surface stays warmer by 1-3°C in winter).
- The improvement is mostly visible in cool climates (NCC zones 6, 7, 8) where the edge thermal bridge is most noticeable.
- The whole-window U-value benefit is typically 5-10% improvement over the same IGU with aluminium spacer.
Cost and supply:
- Warm-edge IGU adds ~10-20% premium over aluminium-spacer equivalent.
- Australian volume manufacturers offer it as standard on mid-to-high-spec lines (Viridian, Capral premium, AWS ThermalHEART).
- Lead time same as the underlying IGU.
Builder takeaway:
- For NCC 2022 / 2025 climate zone 6, 7, 8 residential, specify warm-edge spacer as part of the IGU spec. The energy report and WERS rating reflect the spacer choice.
- Aluminium-spacer IGUs in cool-climate residential will produce visible perimeter condensation that the occupant will complain about; the call-back is not worth the cost saving at spec.
- Verify on delivery: the IGU certificate names the spacer type. Some suppliers substitute aluminium-spacer for warm-edge if not strictly specified.
Also known as: TGI spacer; Super Spacer (brand-specific, often generalised); low-conductivity spacer; thermally improved spacer.
Category: Materials.
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Last updated: 2026-05-16. Verified: 2026-05-16. Quarterly review for currency.