Roof Glazing / Overhead Units
Safety-compliant sealed units for rooflights, skylights and overhead applications. Inner pane MUST be laminated. Solar control and self-cleaning coating options from Pilkington and Saint-Gobain.
Most Popular Rooflight Build
28.0mm all-toughened build — 4mm toughened outer + 20mm argon-filled cavity + 4mm toughened inner (Low-E, warm edge). U-value 1.0. Laminated-inner builds available where the specification calls for them. Add Pilkington Activ for self-cleaning or Suncool for solar control — or choose Activ Blue / Rooflite for a tinted self-cleaning conservatory roof.Roof Glazing — Overhead Safety
Overhead safety guidance calls for a laminated inner (lower) pane — our standard specification — to prevent glass fallout onto occupants below. The outer pane MUST be toughened — we manufacture every overhead unit with a toughened outer as standard for impact resistance against hail, debris and maintenance loads. We also manufacture fully toughened units (toughened both sides) where the project specification or risk assessment allows — common for garden rooms, canopies and smaller panes. Solar control coatings (Pilkington Suncool, SGG Cool-Lite) are essential for south-facing rooflights. Self-cleaning coatings (Pilkington Activ, SGG Bioclean) recommended for hard-to-access installations. For conservatory roofs we also supply Pilkington Activ Blue and Rooflite roof glass — blue-tinted self-cleaning units that combine solar control with a cooler, glare-reduced light, keeping the room usable on bright days.
See how the pitch sheds rain and the laminated inner pane performs overhead:
Configurations
How to read the codes: T6 = 6mm toughened glass · the middle number = cavity width in mm · 6.8L = 6.8mm laminated glass. Example: T6-16-6.8L is a 6mm toughened outer pane, 16mm argon-filled gap, and 6.8mm laminated inner pane.
| Configuration | Thickness | U-Value | g-value | Light | Application |
|---|---|---|---|---|---|
| Lighter 4mm build — 4mm toughened outer + 6.4mm laminated inner code: T4-16-6.4L Low-E Argon | 26.4mm | 1.0 | 0.63 | 80% | Smaller residential rooflights |
| Laminated-inner build — 6mm toughened outer + 6.8mm laminated inner code: T6-16-6.8L Low-E Argon | 28.8mm | 1.0 | 0.61 | 78% | Where a laminated inner is specified |
| ★ Most popular build — all-toughened 4+20+4 — 4mm toughened both sides, 20mm cavity code: T4-20-T4 Low-E Argon | 28.0mm | 1.0 | 0.63 | 80% | Most rooflights — where spec allows |
| All-toughened 6mm — 6mm toughened both sides code: T6-16-T6 Low-E Argon | 28.0mm | 1.0 | 0.61 | 78% | Larger panes — where spec allows |
| Triple glazed — three panes, Passivhaus performance code: T6-12-4-12-6.8L TGU | 40.8mm | 0.7 | 0.50 | 72% | Passivhaus rooflights |
Coated outer pane — add to any build: Suncool 66/33 or 50/25 solar control (cuts solar gain to a third or a quarter), Pilkington Activ self-cleaning, or Activ Blue / Rooflite Blue tinted self-cleaning for conservatory roofs.
Mandatory Requirements
- Laminated inner pane as standard — toughened-both-sides units also manufactured where the specification or risk assessment allows
- Outer pane MUST be toughened — supplied as standard on every CSU overhead unit
- Minimum slope 5° for self-draining
- Solar control STRONGLY recommended for south-facing
Gas Fill — Air as Standard, Argon Optional
CSU sealed units are air-filled as standard. Argon gas fill (minimum 90% concentration) is available as an optional upgrade. Argon has 34% lower thermal conductivity than air (0.018 vs 0.026 W/mK), improving thermal insulation by approximately 15%. Argon is an inert, non-toxic, odourless gas that makes up 0.93% of Earth’s atmosphere — it is inert and environmentally neutral. Krypton gas is available by special order for slim-cavity heritage applications where maximum performance is needed in a narrow gap.
| Property | Dry Air | Argon (Optional) | Krypton (Special) |
|---|---|---|---|
| Thermal Conductivity | 0.026 W/mK | 0.018 W/mK | 0.010 W/mK |
| U-Value Benefit | Reference | ~15% better | ~25% better |
| Optimal Cavity | 12-16mm | 16-20mm | 10-12mm |
| Depletion Rate | N/A | <1% per year | <1% per year |
| Relative Cost | 1× | ~1.2× (included free) | ~50× (premium) |
Spacer Bar Options — Warm Edge vs Aluminium
The spacer bar separates glass panes and creates the sealed cavity. Traditional aluminium spacers conduct heat rapidly (160 W/mK), creating a cold thermal bridge at the unit edge that causes condensation and heat loss. Warm edge spacers use low-conductivity materials, reducing this bridge by up to 94%. CSU recommends Swisspacer Ultimate or Super Spacer TriSeal for all projects.
| Spacer | Material | Conductivity | Psi Value | Edge Temp vs Alu | Colours |
|---|---|---|---|---|---|
| Aluminium | Aluminium alloy | 160.0 W/mK | 0.080 W/mK | Baseline (cold) | Silver, White, Black, Brown, Grey |
| Swisspacer Ultimate | Composite polymer | 0.19 W/mK | 0.030 W/mK | +3-4°C warmer | Black, White, Brown, Grey, Oak +15 |
| Super Spacer TriSeal | Silicone foam | 0.17 W/mK | 0.028 W/mK | +3-4°C warmer | Black, Grey |
| Thermix TX.N Plus | Stainless + plastic | 0.60 W/mK | 0.040 W/mK | +2-3°C warmer | Silver / Black |
| TGI Spacer | Stainless + polymer | 0.90 W/mK | 0.050 W/mK | +1-2°C warmer | Silver |
Warm edge improves Uw by 0.1-0.2 W/m²K, eliminates edge condensation, and can improve WER by one full band. Available in widths: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24mm.
What Overhead Units Weigh
Overhead specs pair a toughened outer with a laminated inner, so they run heavier than a wall unit of the same size — and every kilogram has to go up to roof level:
| Spec | Weight/m² | 600×900 | 1000×1200 | 1500×2000 |
|---|---|---|---|---|
| T6-16-6.8L rooflight DGU | 31 kg/m² | 16.7 kg | 37.2 kg | 93 kg |
| T6-20-10.8L rooflight DGU | 41 kg/m² | 22.1 kg | 49.2 kg | 123 kg |
| 10.8mm laminated (canopy) | 26 kg/m² | 14.0 kg | 31.2 kg | 78 kg |
| 13.5mm laminated (canopy) | 32 kg/m² | 17.3 kg | 38.4 kg | 96 kg |
Weights matter twice overhead: for the lift, and for what the kerb or frame must carry. Check any size on the glass weight calculator.
Site Care for Overhead Glazing
Roof access means lifting gear — book it once and use it for both offloading and fitting. Suction handling covers units to 60 kg; above that it’s mechanical only.
- Store upright on A-frames under weatherproof cover — even walk-on-rated units never lie flat in storage. The laminated edge does the structural work overhead, so it stays protected until the unit is bedded.
- Glaze within 28 days and above 5°C — a sheeted-over rooflight opening shouldn’t wait longer than that.
Lead time depends on the laminate and any walk-on rating — confirmed with your quote.
Related Products & Glass Types
Common Questions
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