{"product_id":"28mm-safety-toughened-double-glazed-unit","title":"28mm Safety Toughened Double Glazed Unit (BS EN 12150)","description":"\n\u003cp class=\"pr-flagship__lede\"\u003e\u003cstrong\u003eSafety glass where it's legally required\u003c\/strong\u003e. A 28mm sealed unit with both panes toughened to BS EN 12150 (Class 1(C)1 impact rating) is the unit Approved Document N of the Building Regulations mandates in \"critical locations\" — areas where human impact on glass is a foreseeable risk.\u003c\/p\u003e\n\n\u003cp\u003e\"Critical location\" is defined in Approved Document N as: glazing at low level (≤ 800mm above floor in walls, ≤ 1500mm in doors), glazing within 300mm of a door edge, glazing in bathrooms or shower enclosures, and glazing in any other location where a person could foreseeably impact the pane. In domestic settings, this typically means: French doors, sidelights, low-level windows in living rooms, conservatory side-panels, and bathroom\/en-suite windows.\u003c\/p\u003e\n\n\u003ch2\u003eTechnical specification\u003c\/h2\u003e\n\u003ctable class=\"pr-spec-table\"\u003e\n  \u003ctr\u003e\n\u003cth\u003eOverall thickness\u003c\/th\u003e\n\u003ctd\u003e28mm\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eBuild-up\u003c\/th\u003e\n\u003ctd\u003e4mm toughened \/ 20mm argon cavity \/ 4mm toughened\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eToughening standard\u003c\/th\u003e\n\u003ctd\u003eBS EN 12150-1 (heat treatment) + BS EN 12600 (impact)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eImpact classification\u003c\/th\u003e\n\u003ctd\u003eClass 1(C)1 (pendulum drop, fall height 1200mm, no penetration)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eBreak pattern\u003c\/th\u003e\n\u003ctd\u003eGranular (small blunt cubes, low laceration risk)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eGas fill\u003c\/th\u003e\n\u003ctd\u003e90% argon\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eU-value (centre-pane, uncoated)\u003c\/th\u003e\n\u003ctd\u003e1.4 W\/m²K\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eU-value (with low-E upgrade)\u003c\/th\u003e\n\u003ctd\u003e1.1 W\/m²K — configurable\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eLight transmittance\u003c\/th\u003e\n\u003ctd\u003e~80%\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eStandards\u003c\/th\u003e\n\u003ctd\u003eBS EN 1279, BS EN 12150, BS EN 12600, BS 6206 (legacy reference)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eWhere the law requires this unit\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFrench doors and patio doors\u003c\/strong\u003e — full-height glazing in entrance\/garden doors must be Class 1(C)1 or laminated equivalent.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDoor sidelights within 300mm of the door edge, up to 1500mm above floor level\u003c\/strong\u003e — Approved Document N, diagram 1.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLow-level windows ≤ 800mm above floor\u003c\/strong\u003e — common in 1990s+ open-plan living rooms with full-height fenestration.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBathroom, en-suite, and wet-room glazing\u003c\/strong\u003e — any location where wet-floor slips toward a window are foreseeable.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eShower enclosures and bath screens\u003c\/strong\u003e — although usually monolithic toughened, sealed-unit specifications occasionally appear in external bathroom windows.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eConservatory side panels and roof bars\u003c\/strong\u003e — overhead glazing (roof) usually requires laminated, not toughened, for fragmentation safety; side panels typically require toughened.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe full safety-glazing decision tree (toughened vs laminated vs heat-strengthened) is on the \u003ca href=\"\/pages\/safety-security-glass\"\u003e\u003cstrong\u003esafety \u0026amp; security glass topical page\u003c\/strong\u003e\u003c\/a\u003e — including the laminated alternative for overhead applications, and the anti-bandit P-rated upgrade path.\u003c\/p\u003e\n\n\u003ch2\u003eToughened vs laminated — which to specify\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eToughened\u003c\/strong\u003e (this flagship): heat-treated glass, breaks into small granular cubes. Strong, impact-resistant, low laceration risk. Cannot be cut or drilled after toughening. Risk: spontaneous breakage from nickel-sulphide inclusion (rare — ~1 in 8 tonnes; mitigable via heat-soak testing for high-risk applications).\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eLaminated\u003c\/strong\u003e: two glass plies with PVB interlayer. On impact, breaks but the interlayer holds the fragments in place. Mandated for overhead glazing (BS 5516), security applications, and where fall-from-height is a risk. Higher cost, slightly lower light transmittance.\u003c\/p\u003e\n\n\u003cp\u003eFor most residential critical locations, toughened is the cost-optimal correct spec. For roof glazing, balconies, balustrades, and security-priority entrances, laminated or heat-soaked-toughened is the right call. The configurator surfaces both options with live pricing.\u003c\/p\u003e\n\n\u003ch2\u003eStock sizes and pricing\u003c\/h2\u003e\n\u003cp\u003eFive UK-standard stock sizes below. Dispatch 5-7 working days (toughening adds ~3 working days vs the standard clear unit). Custom sizes via the \u003ca href=\"\/pages\/configure\"\u003e\u003cstrong\u003econfigurator\u003c\/strong\u003e\u003c\/a\u003e. Trade accounts see tiered pricing.\u003c\/p\u003e\n\n\u003ch2\u003eCertification and standards\u003c\/h2\u003e\n\u003cp\u003eEvery unit carries a permanent BS EN 12150 \/ Kitemark stamp etched in one corner — usually 30mm from the edge, visible in the rebate after fitting. Heat-soak testing (BS EN 14179) is available as an order option for high-risk applications (overhead, large-span, balustrade-adjacent) where spontaneous breakage risk warrants the additional process step.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently asked questions\u003c\/h2\u003e\n\u003ch3\u003eHow do I know if my window is a \"critical location\"?\u003c\/h3\u003e\n\u003cp\u003eMeasure the lowest edge of the pane above the floor. If ≤ 800mm in a wall or ≤ 1500mm in a door (or within 300mm of a door edge), it's critical and needs safety glass. Building Control inspectors will check this on any building-regs-notifiable replacement. \u003ca href=\"\/pages\/safety-security-glass\"\u003eThe topical page\u003c\/a\u003e walks the full Approved Document N decision tree.\u003c\/p\u003e\n\n\u003ch3\u003eCan I tell toughened from regular glass after fitting?\u003c\/h3\u003e\n\u003cp\u003eYes — every toughened pane carries a permanent etched stamp (\"TOUGHENED \/ BS EN 12150 \/ [manufacturer]\") in one corner, usually visible 20-30mm in from the edge inside the rebate or at the corner. Hold a phone torch at a low angle to find it. No stamp = not toughened.\u003c\/p\u003e\n\n\u003ch3\u003eWhy does toughened cost more?\u003c\/h3\u003e\n\u003cp\u003eProcess: regular float glass is cut to size, edge-polished, then heated to ~620°C and rapidly cooled. The differential cooling creates surface compression and central tension — this is what makes it 4-5× stronger than annealed glass. Once toughened, it cannot be cut, drilled, or notched. So all sizing must be exact at the toughening stage, with zero scrap recovery. Premium is typically 15-25%.\u003c\/p\u003e\n\n\u003ch3\u003eCan toughened be combined with low-E?\u003c\/h3\u003e\n\u003cp\u003eYes — but the low-E coating must be hard-coat (Pilkington K) because soft-coat planitherm doesn't survive the 620°C toughening temperature. Configure with \"hard-coat low-E\" for the A-rated + safety stack.\u003c\/p\u003e\n\n\u003ch3\u003eIs toughened secure against intruders?\u003c\/h3\u003e\n\u003cp\u003eNot the right tool. Toughened breaks in one impact event (granular shower) — once broken, there's no residual barrier. For security, specify laminated (BS EN 14449) or anti-bandit P-rated (BS EN 356) glass. The \u003ca href=\"\/pages\/safety-security-glass\"\u003esafety topical page\u003c\/a\u003e covers the security upgrade path.\u003c\/p\u003e\n\n\u003ch3\u003eSpontaneous breakage — should I worry?\u003c\/h3\u003e\n\u003cp\u003eFor most residential applications: no. Nickel-sulphide inclusions causing spontaneous breakage occur at roughly 1 per 8 tonnes of float feedstock. For large-span overhead glazing, balustrades, and high-value retail facades, specify heat-soak-tested (BS EN 14179) toughened — adds ~£8\/m² and reduces NiS risk by \u0026gt;99%.\u003c\/p\u003e\n","brand":"Pane Relief","offers":[{"title":"600 × 400 mm","offer_id":61851583545674,"sku":"DG28-TGH-600x400","price":45.0,"currency_code":"GBP","in_stock":true},{"title":"800 × 600 mm","offer_id":61851583578442,"sku":"DG28-TGH-800x600","price":54.0,"currency_code":"GBP","in_stock":true},{"title":"1000 × 800 mm","offer_id":61851583611210,"sku":"DG28-TGH-1000x800","price":90.0,"currency_code":"GBP","in_stock":true},{"title":"1200 × 1000 mm","offer_id":61851583643978,"sku":"DG28-TGH-1200x1000","price":135.0,"currency_code":"GBP","in_stock":true},{"title":"1500 × 1200 mm","offer_id":61851583676746,"sku":"DG28-TGH-1500x1200","price":203.0,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0895\/3515\/2458\/files\/double-glazed-sealed-unit-igu-product-cutaway_3d8bad1a-08fe-466b-958b-b22c444b99f1.webp?v=1778952477","url":"https:\/\/panerelief.co.uk\/products\/28mm-safety-toughened-double-glazed-unit","provider":"Pane Relief","version":"1.0","type":"link"}