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Double and triple glazing

Sealed units, specified from outside to inside

Build a replacement or new sealed-unit request with separate pane, cavity, spacer and decoration choices. Match the finished unit depth to the frame.

Product guide

Sealed units, specified from outside to inside

Build a replacement or new sealed-unit request with separate pane, cavity, spacer and decoration choices. Match the finished unit depth to the frame.

A modest glazed window with a garden view.
AI-generated illustration. Appearance varies by specification; this is not an exact product sample.

Double-glazed sealed units, triple glazing and replacement insulating glass units

A sealed glass unit combines separate panes, sealed cavities, spacer bars and edge seals. Double glazing has one cavity and triple glazing has two. When replacing a misted unit, the overall depth, finished dimensions, edge detail and frame compatibility matter as well as the number of panes.

Specify the unit from outside to inside. A weather-facing pane may carry a solar-control or self-cleaning function, while another pane may provide low-emissivity coating, privacy, safety or acoustic performance. Coating position and processing need to match the complete build.

Warm-edge spacers, gas fills, obscure patterns, leaded designs, Georgian bars and pet-flap openings are separate specification choices. Slimline heritage units and shaped or stepped units need their own construction review. A generic U-value does not describe every possible combination.

Sealed units, specified from outside to inside for your project

Common enquiry briefs include replace a misted unit, new window or door, conservatory or rooflight, slimline / heritage. Describe the intended use and the supporting construction so the supplier can assess the complete specification. Different applications can need different glass processing, fixings and installation details.

Glass size, cavity and total depth

They are three separate measurements. For example, 4 / 16 / 4 has a 16 mm gap and a 24 mm nominal overall depth.

Design each face

Place appearance and weather-facing functions on the appropriate pane, and confirm coating positions with the fabricator.

Plan decoration early

Bars, leading, patterns, holes and stepped edges need a drawing and may change the manufacturing route.

What to include in a made-to-measure quote

Compare quotes using the same dimensions, quantities, finish, glass construction and installation scope. If you have a drawing or an existing specification, include its reference and identify which details still need advice.

  • Number of panes: Double glazing has one cavity; triple glazing has two.
  • Outer pane: Outside-facing glass. Options vary by processor and the complete build.
  • Inner pane: Room-facing glass; confirm safety processing and the coating surface with the supplier.
  • Middle pane if triple: Choose not applicable for a double unit.
  • Cavity / spacer width: This is the gap, not the total unit thickness. For triple units, record unequal gaps in the notes.
  • Spacer type and colour: Some suppliers restrict warm-edge bars in very narrow cavities.
  • Cavity gas: Gas choice and performance depend on the complete sealed build.
  • Special features: Add pattern names, bar layouts, steps and hole details in your notes. Supplier drawings are required for fabrication.

Cut-to-size dimensions, edges and fabrication

Measure the finished glass only when the fitting allowances and support details are known. Otherwise identify the opening or existing panel you measured and request a survey. Give each different size its own basket line, with its quantity and drawing reference.

Holes, cut-outs, shaped edges and interfaces with hardware should be settled before manufacture. The finished glass construction and any coatings must suit the intended environment. A screen preview or concept photograph cannot replace a sample, survey or product-specific installation drawing.

Supplier checks before manufacture

  • Measure the finished glass unit, not just the visible opening. Confirm fitting clearances with the installer.
  • Total depth is all panes plus all cavities; glazing beads, edge seals and sightline also need to fit.
  • Slimline, roof, shaped and pet-flap builds require supplier confirmation; no generic U-value is promised.

Requesting comparable glass quotes

Save the choices you know and ask for help with the rest. The quote basket records a specification request rather than placing a manufacturing order. A firm quote needs an agreed final build, dimensions, delivery arrangements and any installation or design work.

When comparing proposals, check that glass-only supply and supply with fitting cover the same scope. Ask who provides measurement, drawings, supports, compatible hardware, lifting access and finishing work. Keep the final approved specification with the order.

Sources and further reading

Configure your glass ↓Help me chooseSee the research

Guided specification · Save multiple sizes · Supplier-confirmed quotes

Planning privacy that changes at the touch of a switch? Explore smart switchable glass →

Choose how to specify your sealed units

Need supplier advice?

Use the guided specification. Leave uncertain choices for advice and request a supplier-confirmed price.

Build a quote request ↓

Know the exact pane make-up?

The detailed builder gives indicative estimates for supported combinations. Final price and suitability require supplier confirmation.

Go to the detailed estimator ↓

These are separate forms. Choices are not transferred automatically. Add the same requirement once to avoid duplicate quote lines.

Your glass, step by step

Build your specification

Choose what you know. Leave the rest for a supplier to advise. Add different sizes as separate basket lines.

No account needed to configure
1. Your project

1What are you making?

2. Glass and performance

2Choose the details

Examples and guidanceSealed-unit panes, cavities and edge seal

Double glazing has one cavity; triple glazing has two.

Insulating glass unit sectionTwo separate panes around a sealed cavity; a perimeter spacer and edge seal sit between the panes at the bottom edge.Number of panesIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An insulating glass unit has separate glass panes around one or more sealed cavities. At the perimeter, a spacer maintains separation, with the specified edge-seal system closing the unit. The cavity contains the specified dry air or gas.

A double-glazed unit has two panes and one cavity; a triple-glazed unit has three panes and two cavities. Specify pane types and treatments, cavity widths, spacer, gas and seal compatibility separately.

Examples you may seeA 4 / 16 / 4 example totals 24 mm: 4 mm pane, 16 mm cavity, 4 mm pane.A laminated pane within a sealed unit has its own bonded make-up in addition to the unit cavity.Available choices: Help me choose; Double glazing; Triple glazing.Current choice: Help me choose. This is your request for the supplier to confirm.Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

Double glazing has one cavity; triple glazing has two.

Examples and guidanceSealed-unit panes, cavities and edge seal

Outside-facing glass. Options vary by processor and the complete build.

Insulating glass unit sectionTwo separate panes around a sealed cavity; a perimeter spacer and edge seal sit between the panes at the bottom edge.Outer paneIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An insulating glass unit has separate glass panes around one or more sealed cavities. At the perimeter, a spacer maintains separation, with the specified edge-seal system closing the unit. The cavity contains the specified dry air or gas.

A double-glazed unit has two panes and one cavity; a triple-glazed unit has three panes and two cavities. Specify pane types and treatments, cavity widths, spacer, gas and seal compatibility separately.

Examples you may seeA 4 / 16 / 4 example totals 24 mm: 4 mm pane, 16 mm cavity, 4 mm pane.A laminated pane within a sealed unit has its own bonded make-up in addition to the unit cavity.Available choices: Help me choose; 4 mm clear; 6 mm clear; Toughened clear — thickness to confirm; Laminated safety; Acoustic laminate; Patterned / obscure; Self-cleaning; Solar-control coated.Current choice: Help me choose. This is your request for the supplier to confirm.Flow appearance example of an insulating-unit corner with a dark spacer and perimeter sealAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

Outside-facing glass. Options vary by processor and the complete build.

Examples and guidanceSealed-unit panes, cavities and edge seal

Room-facing glass; confirm safety processing and the coating surface with the supplier.

Insulating glass unit sectionTwo separate panes around a sealed cavity; a perimeter spacer and edge seal sit between the panes at the bottom edge.Inner paneIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An insulating glass unit has separate glass panes around one or more sealed cavities. At the perimeter, a spacer maintains separation, with the specified edge-seal system closing the unit. The cavity contains the specified dry air or gas.

A double-glazed unit has two panes and one cavity; a triple-glazed unit has three panes and two cavities. Specify pane types and treatments, cavity widths, spacer, gas and seal compatibility separately.

Examples you may seeA 4 / 16 / 4 example totals 24 mm: 4 mm pane, 16 mm cavity, 4 mm pane.A laminated pane within a sealed unit has its own bonded make-up in addition to the unit cavity.Available choices: Help me choose; 4 mm low-E soft coat; 6 mm low-E soft coat; Hard-coat low-E; Clear — no coating requested; Laminated / acoustic low-E.Current choice: Help me choose. This is your request for the supplier to confirm.Flow appearance example of an insulating-unit corner with a dark spacer and perimeter sealAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

Room-facing glass; confirm safety processing and the coating surface with the supplier.

Examples and guidanceSealed-unit panes, cavities and edge seal

Choose not applicable for a double unit.

Insulating glass unit sectionTwo separate panes around a sealed cavity; a perimeter spacer and edge seal sit between the panes at the bottom edge.Middle pane if tripleIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An insulating glass unit has separate glass panes around one or more sealed cavities. At the perimeter, a spacer maintains separation, with the specified edge-seal system closing the unit. The cavity contains the specified dry air or gas.

A double-glazed unit has two panes and one cavity; a triple-glazed unit has three panes and two cavities. Specify pane types and treatments, cavity widths, spacer, gas and seal compatibility separately.

Examples you may seeA 4 / 16 / 4 example totals 24 mm: 4 mm pane, 16 mm cavity, 4 mm pane.A laminated pane within a sealed unit has its own bonded make-up in addition to the unit cavity.Available choices: Help me choose; Not applicable — double unit; 4 mm clear; 4 mm low-E; Obscure / privacy; Specified in notes.Current choice: Help me choose. This is your request for the supplier to confirm.Flow appearance example of an insulating-unit corner with a dark spacer and perimeter sealAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

Choose not applicable for a double unit.

Examples and guidanceSealed cavity width and gas request

This is the gap, not the total unit thickness. For triple units, record unequal gaps in the notes.

Insulating glass unit sectionTwo separate panes around a sealed cavity; a perimeter spacer and edge seal sit between the panes at the bottom edge.Cavity / spacer widthIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

The cavity is the sealed separation between adjacent panes. Its width is not the thickness of either pane or the overall unit. Triple glazing has two cavity widths to specify, which may differ.

Dry air and argon requests describe the sealed fill. The manufacturer must confirm the actual fill and the resulting performance for the complete unit; a wider cavity does not automatically improve every performance measure.

Examples you may seeState both cavity widths for a triple-glazed unit.Keep each pane thickness separate when calculating the total glazing depth.Available choices: Help me choose; 4 mm — specialist slimline; 6 mm — specialist slimline; 8 mm; 10 mm; 12 mm; 14 mm; 16 mm; 18 mm; 20 mm; Unequal cavities — see notes.Current choice: Help me choose. This is your request for the supplier to confirm.Flow appearance example of an insulating-unit corner with a dark spacer and perimeter sealAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

This is the gap, not the total unit thickness. For triple units, record unequal gaps in the notes.

Examples and guidanceSealed-unit spacer and perimeter seals

Some suppliers restrict warm-edge bars in very narrow cavities.

Unit perimeter detailClose-up assembled unit edge: spacer at perimeter, cavity above, specified sealing system around the edge.Spacer type and colourIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

The spacer runs around the perimeter between panes. It sets the pane separation at the edge; the cavity extends across the viewing area. Desiccant and the specified seals form part of the manufactured unit’s edge system.

Spacer appearance and warm-edge options are separate from cavity width and gas selection. Confirm the proposed spacer dimensions, sightline and edge-seal compatibility with the frame and glazing materials.

Examples you may seeWarm-edge spacer request: confirm the actual spacer product and colour.Replacement unit: check visible sightline and frame coverage as well as total depth.Available choices: Help me choose; Warm edge — black; Warm edge — grey; Warm edge — white; Aluminium — silver; Aluminium — gold; Aluminium — bronze.Current choice: Help me choose. This is your request for the supplier to confirm.Flow appearance example of an insulating-unit corner with a dark spacer and perimeter sealAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

Some suppliers restrict warm-edge bars in very narrow cavities.

Examples and guidanceSealed cavity width and gas request

Gas choice and performance depend on the complete sealed build.

Insulating glass unit sectionTwo separate panes around a sealed cavity; a perimeter spacer and edge seal sit between the panes at the bottom edge.Cavity gasIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

The cavity is the sealed separation between adjacent panes. Its width is not the thickness of either pane or the overall unit. Triple glazing has two cavity widths to specify, which may differ.

Dry air and argon requests describe the sealed fill. The manufacturer must confirm the actual fill and the resulting performance for the complete unit; a wider cavity does not automatically improve every performance measure.

Examples you may seeState both cavity widths for a triple-glazed unit.Keep each pane thickness separate when calculating the total glazing depth.Available choices: Help me choose; Argon; Air; Krypton — specialist quote.Current choice: Help me choose. This is your request for the supplier to confirm.Flow appearance example of an insulating-unit corner with a dark spacer and perimeter sealAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

Gas choice and performance depend on the complete sealed build.

Examples and guidanceSealed-unit bars, patterns and special details

Add pattern names, bar layouts, steps and hole details in your notes. Supplier drawings are required for fabrication.

Fabrication drawing conceptsFront elevation concepts with hole centres and a decorative bevel. Confirm the hardware drawing and processing limits.Special featuresIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

Decorative bars, lead designs, patterns and prepared openings need an agreed drawing for the actual unit. Specify whether a detail is inside the cavity, on a surface or part of an approved glazing accessory.

A pet-flap opening or unusual edge detail must be manufactured as part of a supplier-confirmed construction with suitable edge sealing. Do not plan to cut or drill a completed sealed unit on site. Match the accessory model and frame coverage before ordering.

Examples you may seeBar layout: provide a dimensioned elevation and identify both viewing directions.Prepared opening: give the exact accessory model and ask the unit manufacturer to confirm feasibility.Available choices: Help me choose; Plain unit; Georgian bars; Leaded design; Duplex bars; Pet-flap hole; Stepped / shaped unit; Multiple features — see notes.Current choice: Help me choose. This is your request for the supplier to confirm.Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗

Add pattern names, bar layouts, steps and hole details in your notes. Supplier drawings are required for fabrication.

3. Sizes and fabrication notes

3Size and quantity

Enter finished glass sizes. If you only have opening sizes, ask for a survey or fitting allowance before ordering.

Examples and guidancePanel outline and drawing

Choose the finished outline. A rectangle needs width and height; a circle needs diameter. Bespoke shapes need enough dimensions, radii and datum references to define the outline.

Panel dimension referenceFinished rectangular panel width and height. Opening dimensions are a different reference.ShapeIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

A preview is an illustration; ask the supplier to confirm the manufacturing drawing or template.

Examples you may seeRectangle or square: finished width and height.Circle: diameter, with hole or cut-out positions separately documented.Available choices: Rectangle; Circle; Shaped / drawing to follow.Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: glass types (opens in a new tab) ↗
Examples and guidanceMeasurement units

1 cm equals 10 mm. Choose the units before entering sizes; keep drawing annotations in the same units.

Panel dimension referenceFinished rectangular panel width and height. Opening dimensions are a different reference.Measurement unitsIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

The form converts entered measurements to the existing millimetre specification fields.

Examples you may see120 cm = 1,200 mm.60 cm = 600 mm.Available choices: Millimetres (mm); Centimetres (cm).Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: glass types (opens in a new tab) ↗
Examples and guidanceFinished panel dimensions

Record the finished width and height of each distinct panel. For a circle use its diameter; shaped work needs a dimensioned drawing or agreed template.

Panel dimension referenceFinished rectangular panel width and height. Opening dimensions are a different reference.Width ( mm )Illustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An opening, frame and finished glass are different references. Request a survey when the finished manufacturing dimensions remain unknown.

Examples you may seeOne size per basket line; quantity records identical pieces.Check units and the dimension reference before confirming manufacture.Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: glass types (opens in a new tab) ↗
Examples and guidanceFinished panel dimensions

Record the finished width and height of each distinct panel. For a circle use its diameter; shaped work needs a dimensioned drawing or agreed template.

Panel dimension referenceFinished rectangular panel width and height. Opening dimensions are a different reference.Height ( mm )Illustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An opening, frame and finished glass are different references. Request a survey when the finished manufacturing dimensions remain unknown.

Examples you may seeOne size per basket line; quantity records identical pieces.Check units and the dimension reference before confirming manufacture.Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: glass types (opens in a new tab) ↗
Examples and guidanceQuantity of identical pieces

Quantity counts pieces with the same size and specification. Enter different sizes or constructions as separate basket lines so each requirement is retained.

Numbered specification scheduleA numbered schedule separates panel specification, hardware, delivery, fitting and approvals.QuantityIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

Examples you may seeThree identical panels: quantity 3.Two distinct sizes: separate lines.Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: glass types (opens in a new tab) ↗
Examples and guidanceSealed-unit panes, cavities and edge seal

An insulating glass unit has separate glass panes around one or more sealed cavities. At the perimeter, a spacer maintains separation, with the specified edge-seal system closing the unit. The cavity contains the specified dry air or gas.

Insulating glass unit sectionTwo separate panes around a sealed cavity; a perimeter spacer and edge seal sit between the panes at the bottom edge.Required total unit depth (mm)Illustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

A double-glazed unit has two panes and one cavity; a triple-glazed unit has three panes and two cavities. Specify pane types and treatments, cavity widths, spacer, gas and seal compatibility separately.

Examples you may seeA 4 / 16 / 4 example totals 24 mm: 4 mm pane, 16 mm cavity, 4 mm pane.A laminated pane within a sealed unit has its own bonded make-up in addition to the unit cavity.Flow appearance example of an insulating-unit corner with a dark spacer and perimeter sealAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: laminated and insulating glass constructions (opens in a new tab) ↗
Optional. Include every pane and cavity; match the frame and glazing beads.
Examples and guidanceDrawing references and unresolved details

Record drawing references, site conditions and requirements not captured in the choices. Identify anything that needs a survey or supplier confirmation before manufacture.

Numbered specification scheduleA numbered schedule separates panel specification, hardware, delivery, fitting and approvals.Project and fabrication notesIllustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

Examples you may seeNumber drawings and panel positions consistently.State access constraints and the requested work scope.Sealed units, specified from outside to inside: original Flow application conceptAI-generated product illustration from Google Flow; not an exact product sample, completed installation or proof of performance.Guardian: glass types (opens in a new tab) ↗

0/2000 characters. Share drawings and photos in the job conversation after submitting.

Detailed sealed-unit estimator

For supported pane combinations and indicative performance. This form starts separately from the guided enquiry above and does not import its choices. Specialist slimline cavities, decorative features, different middle panes and unequal cavities should remain in the guided specification for supplier pricing. Add each requirement once.

Open the detailed sealed-unit builder

01 · Unit type

02 · Glass panes

Outer Clear 4mm · Inner Laminated 6.8mm

Outer pane

Clear float

Toughened

Laminated safety

Acoustic

Low-iron

Inner pane

Clear float

Toughened

Laminated safety

Acoustic

Low-iron

Low-E coating position

One low-E coating is modelled (the validated engine tier). Two-coat builds are quoted verbatim by suppliers — add a note at checkout.

03 · Cavity, gas & spacer

Cavity width

1 × 16mm

Gas fill

the default — cheap and effective

Spacer bar

Spacer colour

Standard colours shown. Bespoke RAL-coded bars can be requested on specialist projects — add it as a note at checkout.

Warm-edge spacers lower the whole-window U-value (linear ψ 0.06 W/mK). Colour choice doesn't change performance.

04 · Unit size

Examples and guidanceFinished panel dimensions

Record the finished width and height of each distinct panel. For a circle use its diameter; shaped work needs a dimensioned drawing or agreed template.

Panel dimension referenceFinished rectangular panel width and height. Opening dimensions are a different reference.Width (mm)Illustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An opening, frame and finished glass are different references. Request a survey when the finished manufacturing dimensions remain unknown.

Examples you may seeOne size per basket line; quantity records identical pieces.Check units and the dimension reference before confirming manufacture.Guardian: glass types (opens in a new tab) ↗
Examples and guidanceFinished panel dimensions

Record the finished width and height of each distinct panel. For a circle use its diameter; shaped work needs a dimensioned drawing or agreed template.

Panel dimension referenceFinished rectangular panel width and height. Opening dimensions are a different reference.Height (mm)Illustrative schematic, not to scale or a fabrication / fixing specification.

What your choice means

An opening, frame and finished glass are different references. Request a survey when the finished manufacturing dimensions remain unknown.

Examples you may seeOne size per basket line; quantity records identical pieces.Check units and the dimension reference before confirming manufacture.Guardian: glass types (opens in a new tab) ↗
Overall sealed-unit depth 26.8mm — check your frame rebate (the slot the unit sits in) accepts it.Weight 25.8 kg/m²1000 × 1000 mm = 1 m² actual glass area

Before you choose

The decisions that matter

01

Glass size, cavity and total depth

They are three separate measurements. For example, 4 / 16 / 4 has a 16 mm gap and a 24 mm nominal overall depth.

02

Design each face

Place appearance and weather-facing functions on the appropriate pane, and confirm coating positions with the fabricator.

03

Plan decoration early

Bars, leading, patterns, holes and stepped edges need a drawing and may change the manufacturing route.

Ready for a useful supplier quote

  • Measure the finished glass unit, not just the visible opening. Confirm fitting clearances with the installer.
  • Total depth is all panes plus all cavities; glazing beads, edge seals and sightline also need to fit.
  • Slimline, roof, shaped and pet-flap builds require supplier confirmation; no generic U-value is promised.
Compare detailed pane make-ups and modelled performance →

Research behind these choices

Reviewed 23 October 2026. Manufacturer guidance and supplier ordering pages inform these design questions. Agree the final construction and project requirements with your supplier.

Useful questions

Can I get a quote before I know every detail?

Yes. Choose Help me choose where you need advice, or request a site measurement. Suppliers can review the brief; a firm manufacturing price needs an agreed final specification.

Does adding a panel place an order?

No. It saves a specification in your quote basket. Review the basket and provide your delivery details to request supplier quotes. Your configuration does not approve the product for installation.

What should I confirm for insulating glass units (igu / dgu / tgu)?

Measure the finished glass unit, not just the visible opening. Confirm fitting clearances with the installer. Total depth is all panes plus all cavities; glazing beads, edge seals and sightline also need to fit. Slimline, roof, shaped and pet-flap builds require supplier confirmation; no generic U-value is promised.

Compare related glass

Low-E coated glass →Solar control glass →Self-cleaning glass →Laminated glass →Heated double-glazed units →