- TYPE: Triple Glazing
Triple Glazed Window Unit - Standard
- Estimated lead time: 6 weeks
- Energy Rating (A–G): —
- Building Reg Compliance: Part L 2021 Compliant
- Warranty Period: 15 years
- Installation Required: Yes
Building Regulations require toughened glass for doors. This will be automatically applied.
Safety glass that holds together when broken - required for overhead glazing
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1200×1400mm Pilkington K Glass
Description
Triple Glazed Window Unit — Residential Casement Windows
The casement window — side-hung or top-hung — is the most common window type in UK homes. Our Triple Glazed Window Unit is engineered to fit the frame profiles used by leading casement window manufacturers, delivering U-values from 0.7 to 0.9 W/m²K in the most popular window format.
Whether you're replacing failed sealed units in existing casement frames or specifying new windows for a renovation, our triple-glazed units drop straight into most modern uPVC, aluminium, and timber casement systems. The result: a step-change in thermal and acoustic performance without changing your window style.
Specification
Our standard triple-glazed window units are available in 28mm, 32mm, and 36mm overall thickness to suit different frame systems. All units include Low-E coating and argon gas fill as standard.
- U-value: 0.7–0.9 W/m²K (depending on build-up)
- Thickness options: 28mm, 32mm, 36mm
- Low-E coating: Included as standard
- Gas fill: Argon (90%+)
- Glass options: Clear, obscure, tinted, solar control
Compatible with most modern window frame systems including uPVC, aluminium, timber, and composite. Custom sizes manufactured to order.
Manufactured to BS EN 1279 at our Bristol facility. FENSA registered, 10-year warranty, nationwide delivery.
Use our glass configurator to specify your frame system, dimensions, and glass preferences for instant pricing.
Material
Glass Composition
Three panes of 4mm float glass with Low-E coating and argon gas fill as standard. The overall thickness depends on cavity width: 28mm (8mm cavities), 32mm (10mm cavities), or 36mm (12mm cavities). Wider cavities deliver better thermal and acoustic performance.
Low-E coating position: soft-coat on surface 5 (28mm single-coating option) or surfaces 3 and 5 (32mm and 36mm double-coating option). Double coating delivers the lowest U-values.
Warm-edge or aluminium spacer bars available. Warm-edge spacers are recommended for living spaces where edge condensation would be noticeable — they maintain a warmer inner-pane perimeter temperature, reducing moisture risk.
Care
Cleaning & Maintenance
Your triple glazed window unit requires minimal ongoing maintenance to deliver decades of reliable performance. Regular cleaning keeps glass looking its best and helps identify any issues early.
Routine Cleaning
Clean both faces of the sealed unit using warm water with a small amount of washing-up liquid and a soft, lint-free cloth or sponge. Avoid abrasive cleaners, scouring pads, or razor blades, which can damage coatings and seals. Rinse thoroughly with clean water and dry with a chamois or microfibre cloth to prevent water spots.
Seal & Spacer Bar Inspection
Inspect the perimeter seal every 6–12 months. Look for cracking, peeling, or gaps in the secondary sealant (typically black polysulphide or silicone). If you notice internal condensation between the panes, this indicates seal failure — contact Pane Relief for a warranty assessment.
Frame & Drainage
Keep drainage slots in the window frame clear of debris. Blocked drainage channels allow water to pool against the sealed unit edge, which accelerates seal degradation. A pipe cleaner or compressed air clears most blockages.
Installation
Installation Guide
Correct installation is critical to the long-term performance of your triple glazed window unit. These guidelines cover standard rebated-frame glazing — always refer to the frame manufacturer's instructions for system-specific requirements.
Preparation
Inspect the unit on delivery. Check for chips, cracks, or seal damage before removing protective film. Verify dimensions match the frame rebate with 3–5mm clearance on all sides. Ensure the frame rebate is clean, dry, and free from old putty or sealant residue.
Setting Blocks & Packers
Place two setting blocks (minimum 50mm wide) at the quarter points of the bottom rail — approximately 50mm from each corner. Use 5mm flat packers for side and top clearance. Setting blocks must be load-bearing nylon or HDPE, not timber, which can swell and crack the glass.
Glazing & Sealing
Apply a continuous bead of neutral-cure silicone sealant to the back of the glazing bead before pressing into position. Do not use acid-cure silicone, which attacks the spacer bar sealant. Ensure the glazing bead is fully seated with no gaps — water ingress behind the bead is the most common cause of premature seal failure.
Drainage
Verify that frame drainage slots (minimum two per unit, positioned at the lowest point of the rebate) are clear and functional. The sealed unit must never sit in standing water.
Window-Specific Notes
Verify frame compatibility before ordering — check the frame manufacturer's maximum glazing thickness specification. Most modern triple-glazing frame profiles accept 28–44mm, but older frames designed for double glazing may only accommodate 24–28mm. For sash windows, check the balance system weight rating against the triple-glazed unit weight (approximately 30% heavier than double glazing of the same dimensions).
Warranty
10-Year Manufacturer's Warranty
Every triple glazed window unit from Pane Relief is backed by our comprehensive 10-year manufacturer's warranty, covering seal integrity, gas retention, and coating performance. Our BS EN 1279-certified manufacturing process ensures each unit meets the highest quality standards.
The warranty covers: internal condensation caused by seal failure, visible coating degradation, and argon or krypton gas leakage beyond acceptable levels. Normal wear, external condensation (a sign the unit is working efficiently), and damage from incorrect installation or handling are excluded.
To make a claim, contact our Bristol team with your order reference and date of purchase. We aim to inspect and resolve all warranty claims within 14 working days. For installations carried out by FENSA-registered installers, we can process claims directly — no third-party paperwork required.
Shipping & Returns
- Free shipping on orders over £250
- Standard delivery within 2–5 business days
- Easy 30-day returns
- Return items in original condition for a full refund
Standard delivery within 2–5 business days
Return items in original condition for a full refund
Need a Custom Size?
Use our glass configurator to specify exact dimensions, gas fills, coatings, and more — with instant trade pricing.
Frequently Asked Questions
Everything you need to know about this product before ordering.
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Our insulated glass units achieve U-values as low as 1.0 W/m²K with argon gas fill and low-emissivity coatings. The exact U-value depends on your chosen glass specification, spacer bar type, and gas fill. We can provide a detailed thermal calculation for your specific configuration on request.
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Yes, we manufacture bespoke units to your exact specifications. Simply provide the width, height, and glass configuration you need. There is no minimum order quantity for custom sizes, and we can accommodate most non-standard shapes including arched, circular, and raked units.
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Standard units ship within 2–3 weeks from order confirmation. Custom specifications such as toughened, laminated, or triple-glazed units may take 3–4 weeks depending on glass availability. We will confirm the exact lead time when we process your order.
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We supply direct to trade — our units are designed for professional installation by qualified glaziers and window fitters. Each unit ships with fitting instructions and gasket recommendations. If you need installation support, we can recommend approved installers in your area.
How to Replace a Sealed Unit
Follow these steps for a professional sealed unit replacement. Always wear protective gloves and eyewear when handling glass.
Measure the Opening
Measure the width and height of the glass (not the frame) in at least three places. Take the smallest measurement and deduct 2mm for clearance. This gives you your order size.
Remove the Beading
Starting with the longest bead, insert a stiff putty knife or glazing chisel into the gap between bead and frame. Gently lever outward. For uPVC, the bead will unclip. For timber, carefully prise the pinned bead away.
Remove the Old Unit
Using suction cups, carefully lift the failed sealed unit out of the frame. Tilt the top edge toward you first, then lift clear. Have a second person assist with larger units.
Clean the Frame Rebate
Remove any old sealant, dirt, or glazing tape from the rebate using a scraper and white spirit. The rebate must be clean and dry for the new unit to sit properly and for sealant to adhere.
Position the Packers
Place setting blocks at the quarter and three-quarter points along the bottom of the frame. These support the weight of the glass and ensure even distribution. Use 5mm packers for standard units.
Insert the New Sealed Unit
Lower the new unit into the frame, resting it on the packers. Push the unit back into the rebate until it sits square. Check that the gap is even all around — adjust packers if needed.
Refit the Beading
Starting with the shortest bead, press each one firmly back into position. For uPVC, tap with a rubber mallet until it clicks home. For timber, pin back in place. Ensure all beads are flush with the frame.
Check & Finish
Use a spirit level to confirm the unit is sitting level. Check all four edges for even gaps. Clean the glass with a soft cloth. The new unit should operate smoothly within the window.
Not confident doing this yourself? We offer professional installation across Bristol and the South West.
Need Help? Contact UsTrade Support
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