{"product_id":"14mm-slim-krypton-conservation-double-glazed-unit","title":"14mm Slim Krypton Double Glazed Unit (Conservation)","description":"\n\u003cp class=\"pr-flagship__lede\"\u003e\u003cstrong\u003eHeritage-aperture double glazing where rebate depth is the constraint\u003c\/strong\u003e. A 14mm slim krypton-filled sealed unit (4mm clear \/ 6mm krypton cavity with soft-coat low-E \/ 4mm clear) is the conservation-officer-friendly double-glazing spec — engineered for Georgian and Victorian timber sashes, listed-building consents, and conservation-area replacement where a 24mm or 28mm unit will not fit the original rebate.\u003c\/p\u003e\n\n\u003cp\u003eSlim double-glazed units exist for one reason: the original glazing rebate in a pre-1920s timber sash was cut for 4mm single glazing — typically 8-12mm deep. A standard 24mm modern unit simply will not seat in that rebate without re-cutting the sash (which most listed-building consents prohibit) or fitting bulky surface-mounted secondary glazing (which conservation officers usually reject on sightline grounds). Slim units squeeze a true argon-or-krypton-filled IGU into a 14mm overall depth — sometimes less — and let original joinery stay intact.\u003c\/p\u003e\n\n\u003ch2\u003eWhy krypton, not argon, in this build\u003c\/h2\u003e\n\u003cp\u003eCavity gas performance is a function of cavity depth. In a 16mm cavity (the standard 24mm unit) argon is optimal — krypton offers no further U-value benefit and costs five times more. Below 10mm, argon's convective performance degrades and krypton becomes the better insulator. At a 6mm cavity (this unit), krypton drops centre-pane U-value from ~2.0 (argon) to ~1.6 (krypton) — a meaningful 20% improvement at a cavity depth where every fraction of a watt matters.\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\u003e14mm (nominal — tolerance ±0.5mm)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eBuild-up\u003c\/th\u003e\n\u003ctd\u003e4mm clear \/ 6mm krypton cavity \/ 4mm clear with Planitherm Total+ soft-coat (face 3)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eGas fill\u003c\/th\u003e\n\u003ctd\u003e≥90% krypton (BS EN 1279-3 verified)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eSpacer bar\u003c\/th\u003e\n\u003ctd\u003eWarm-edge composite, black slim-profile (typ. 5-6mm)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eU-value (centre-pane)\u003c\/th\u003e\n\u003ctd\u003e1.6 W\/m²K\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eU-value (whole window, sash + glass)\u003c\/th\u003e\n\u003ctd\u003e~1.9-2.1 W\/m²K depending on frame\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eg-value\u003c\/th\u003e\n\u003ctd\u003e0.63\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eLight transmittance\u003c\/th\u003e\n\u003ctd\u003e~78%\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eSightline \/ cavity-edge appearance\u003c\/th\u003e\n\u003ctd\u003e~12-15mm visible from outside (matches single-glazed sightline within heritage tolerance)\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003ctr\u003e\n\u003cth\u003eStandards\u003c\/th\u003e\n\u003ctd\u003eBS EN 1279 (parts 1-6), BS EN 673 (U-value), Historic England slim-DG guidance compatible\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eWhere this unit is the right call\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eListed buildings (Grade II, II*, I)\u003c\/strong\u003e where the conservation officer has accepted slim double glazing as a \"like-for-like\" replacement of failed single glazing.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eConservation area consents\u003c\/strong\u003e in cities like Bath, Edinburgh, Brighton, and Oxford where original sash sightlines are protected.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eGeorgian, Regency, and Victorian timber sashes\u003c\/strong\u003e with original glazing rebates 8-14mm deep — fits without re-rebating.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHeritage shopfronts and ecclesiastical glazing\u003c\/strong\u003e where leaded-light, crown-glass, or stained-glass aesthetics must be preserved at the sightline.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eProperties in Article 4 direction areas\u003c\/strong\u003e where windows are subject to planning control and full-thickness DG would breach consent conditions.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eSlim double glazing's tradeoffs, conservation-officer evidence-pack templates, and the case for slim Krypton over secondary glazing are covered in depth on the \u003ca href=\"\/pages\/slim-double-glazing\"\u003e\u003cstrong\u003eslim double glazing topical page\u003c\/strong\u003e\u003c\/a\u003e — including a checklist for evidencing slim DG to a conservation officer.\u003c\/p\u003e\n\n\u003ch2\u003eStock sizes and pricing\u003c\/h2\u003e\n\u003cp\u003eFive UK-standard stock sizes are listed below. Each is dispatched 10-14 working days from order (slim-cavity krypton manufacturing is a specialist process — longer lead time than standard 24mm DG). Custom sizes — including arched-top, raked, leaded-effect overlay, and conservation-bar-compatible variants — are priced via the \u003ca href=\"\/pages\/configure\"\u003e\u003cstrong\u003eonline glass configurator\u003c\/strong\u003e\u003c\/a\u003e.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eNote on listed-building consent:\u003c\/strong\u003e these units are manufactured to a specification accepted by most UK conservation officers under \"minimal intervention\" principles, but consent is always property-specific. We can supply a technical pack (cavity-depth diagram, gas-retention test data, BS EN 1279 DoP) for inclusion in your application — request via \u003ca href=\"\/pages\/contact-us\"\u003eour contact form\u003c\/a\u003e at order.\u003c\/p\u003e\n\n\u003ch2\u003eCertification and standards\u003c\/h2\u003e\n\u003cp\u003eUKCA-marked, BS EN 1279 compliant across all six parts. Krypton gas fill is verified per BS EN 1279-3 at initial fill ≥90% with annual loss \u0026lt;1% under EN-1279-2 accelerated weathering. Slim-cavity construction adds a 6th-part test for capillary water ingress at the warm-edge interface — every batch carries a hydrostatic pressure cycle stamp.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently asked questions\u003c\/h2\u003e\n\u003ch3\u003eWill a conservation officer accept this?\u003c\/h3\u003e\n\u003cp\u003eUsually yes — slim DG is now widely accepted across UK local authorities under Historic England's \u003cem\u003eEnergy Efficiency and Historic Buildings\u003c\/em\u003e guidance (2018). Acceptance is property-specific: officers in Bath and Edinburgh are typically more conservative than rural authorities. The case is strongest when (a) the original single-glazed unit has failed, (b) the slim unit matches the original sightline within 2-3mm, and (c) you submit a manufacturer's spec sheet showing BS EN 1279 compliance. Pre-submission consultation with the officer is recommended.\u003c\/p\u003e\n\n\u003ch3\u003eHow does this compare to secondary glazing?\u003c\/h3\u003e\n\u003cp\u003eSecondary glazing adds an internal pane in a separate frame, leaving the original glazing intact. It performs well thermally (U ~1.8 W\/m²K combined) and excellently acoustically (Rw up to 45 dB). But it's visible, adds maintenance complexity, and many conservation officers consider it less sympathetic than slim DG. Slim DG replaces the failed unit at the existing sightline. The right call depends on the property and the officer.\u003c\/p\u003e\n\n\u003ch3\u003eWhat's the cavity depth tolerance?\u003c\/h3\u003e\n\u003cp\u003e6mm nominal ± 0.5mm. Edge-seal compression during sealing introduces a small reduction. For a 14mm overall unit, this means the sash rebate needs at least 14.5mm depth with 2-3mm of clearance for fitting putty or beading — total 17mm minimum.\u003c\/p\u003e\n\n\u003ch3\u003eKrypton retention — does it leak out?\u003c\/h3\u003e\n\u003cp\u003eIndustry standard is \u0026lt;1% per year under EN-1279-2 accelerated weathering. Over 25 years that's \u0026lt;22% total loss — at 78% krypton + 22% air, centre-pane U-value rises from 1.6 to ~1.7 W\/m²K. The warm-edge spacer's gas-permeation barrier is the critical component; warranty is 10 years on krypton retention to 80% of initial fill.\u003c\/p\u003e\n\n\u003ch3\u003eCan I add laminated panes for acoustic or security?\u003c\/h3\u003e\n\u003cp\u003eYes via configurator — 6.4mm acoustic laminated outer with 4mm clear inner adds about 2mm to overall thickness (16mm total). This is the recommended combo for slim DG in conservation areas backing onto noisy streets. Rw improves to ~36-38 dB while preserving the heritage sightline.\u003c\/p\u003e\n\n\u003ch3\u003eWhat's the price premium vs standard 24mm DG?\u003c\/h3\u003e\n\u003cp\u003eRoughly 40-50%. Krypton fill alone is ~5× the cost of argon; the slim-cavity manufacturing process adds further premium because edge-seal tolerances are tighter and yield rates are lower. The configurator surfaces the live per-m² rate so you can compare against the standard 24mm A-rated double.\u003c\/p\u003e\n\n\u003ch3\u003eWarranty?\u003c\/h3\u003e\n\u003cp\u003e10 years on edge-seal integrity (BS EN 1279-2). 10 years on krypton retention to ≥80% of initial fill. 5 years on the Planitherm soft-coat (Saint-Gobain batch certification). Listed-building installations are warranted on the same terms — installation must be by a competent person familiar with heritage joinery.\u003c\/p\u003e\n","brand":"Pane Relief","offers":[{"title":"600 × 400 mm","offer_id":61853203857738,"sku":"DG14-SLIMKR-600x400","price":45.0,"currency_code":"GBP","in_stock":true},{"title":"800 × 600 mm","offer_id":61853203890506,"sku":"DG14-SLIMKR-800x600","price":72.0,"currency_code":"GBP","in_stock":true},{"title":"1000 × 800 mm","offer_id":61853203923274,"sku":"DG14-SLIMKR-1000x800","price":119.0,"currency_code":"GBP","in_stock":true},{"title":"1200 × 1000 mm","offer_id":61853203956042,"sku":"DG14-SLIMKR-1200x1000","price":179.0,"currency_code":"GBP","in_stock":true},{"title":"1500 × 1200 mm","offer_id":61853203988810,"sku":"DG14-SLIMKR-1500x1200","price":268.0,"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_51f79282-bd42-42e4-98b1-9e82f9e659e8.webp?v=1779007266","url":"https:\/\/panerelief.co.uk\/products\/14mm-slim-krypton-conservation-double-glazed-unit","provider":"Pane Relief","version":"1.0","type":"link"}