- TYPE: Triple Glazing
Triple-Glazed Passive House IGU
- Estimated lead time: 34 weeks
- Energy Rating (A–G): A
- Building Reg Compliance: 445
- Warranty Period: 25 years
- Installation Required: Yes
Building Regulations require toughened glass for doors. This will be automatically applied.
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1200×1400mm Pilkington K Glass
Description
Triple-Glazed Passive House IGU — Ultra-Low Energy Certified Glazing
Engineered for Passivhaus-certified builds and ultra-low energy construction, this triple-glazed insulated glass unit delivers a centre-pane U-value of 0.5 W/m²K or better — the gold standard in thermal performance. If you're building to Passive House standards, this is the sealed unit your project demands.
Pane Relief manufactures these premium IGUs at our Bristol facility using three panes of high-clarity float glass with triple soft-coat Low-E coatings and krypton gas fill. The warm-edge spacer bar (ψ ≤ 0.030 W/mK) virtually eliminates thermal bridging at the glass edge — a critical detail that separates genuine Passive House glazing from standard triple units.
Why Passive House Glazing Matters
Passive House certification requires the entire building envelope to meet stringent thermal targets. Standard triple glazing with U-values of 0.7–0.9 W/m²K won't qualify. Our Passive House IGU closes the gap between wall insulation and glazing performance, ensuring windows aren't the weak link in your thermal envelope.
- Centre-pane U-value: ≤0.5 W/m²K
- Overall thickness: 44–52mm depending on configuration
- Gas fill: Krypton (superior to argon for thinner cavities)
- Warm-edge spacer: ψ ≤ 0.030 W/mK
- Light transmittance: ~60% (excellent for triple Low-E)
- Solar factor (g-value): ~0.35
Every unit is manufactured to BS EN 1279 and can be supplied with test certificates for your Passive House certifier. We work directly with PHI-certified designers and can provide ψ-value calculations for specific frame combinations on request.
As a FENSA-registered manufacturer based in Bristol, we offer nationwide UK delivery with fully insured transit packaging rated for Passive House-grade glass. All units carry our 10-year manufacturer's warranty.
Use our glass configurator to specify your exact dimensions, glass combination, and spacer bar requirements — you'll receive an instant quote tailored to your Passive House project.
Material
Glass Composition
This Passive House IGU uses three panes of premium float glass — typically 4mm-4mm-4mm — separated by two gas-filled cavities. Each cavity is filled with krypton gas at 90%+ concentration, chosen over argon because krypton delivers 40% lower thermal conductivity in the narrower cavities required for Passive House frame compatibility.
Three separate soft-coat Low-E layers are applied to surfaces 2, 3, and 5 (counting from outside). This triple-coating configuration reflects long-wave infrared radiation back into the building while allowing visible light to pass through — achieving the sub-0.5 U-value without resorting to tinted or reflective glass.
The warm-edge spacer bar is constructed from composite materials with a thermal conductivity of ≤0.030 W/mK, compared to ~160 W/mK for traditional aluminium spacers. This eliminates the cold edge band that causes internal condensation at the glass perimeter — a visible sign of thermal bridging that Passive House assessors flag as a defect.
Primary seal: polyisobutylene (PIB). Secondary seal: two-part polysulphide or structural silicone depending on frame system requirements. Desiccant-filled spacer bars absorb residual moisture within the cavity.
Care
Cleaning & Maintenance
Your Passive House IGU 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.
Condensation — External
External condensation (on the outer face of the glass) is common with high-performance units — it indicates the glass is insulating so effectively that the outer pane drops below the dew point. This is a sign your unit is working correctly and requires no action. It typically clears within an hour of sunrise.
Installation
Installation Guide
Correct installation is critical to the long-term performance of your Passive House IGU. 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.
Passive House-Specific Notes
Ensure the frame installation follows PHI-certified thermal bridge-free details. The warm-edge spacer must align with the insulation plane of the wall build-up. Use vapour-permeable tape on the external face and airtightness tape on the internal face — not expanding foam alone, which does not provide a reliable air barrier.
Record the unit serial numbers for your Passive House certification file. We supply a certificate of conformity with every order that includes U-value, g-value, and ψ-spacer data in the format required by PHPP (Passive House Planning Package).
Warranty
10-Year Manufacturer's Warranty
Every Passive House IGU 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
Technical Specifications
Performance data you can rely on
Thermal Performance
Safety & Compliance
| Property | Value | |
|---|---|---|
| Thermal Performance | ||
| Energy Rating | {"scale_min":"1.0","scale_max":"10.0","value":"7.0"} | |
| Safety & Compliance | ||
| Certification | BSI | |
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.
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