Training Example: Double Glazing Units – Review the Data, Give Your Score & Compare to the Real AI Evaluation

Trusted UK Supplier & Installer
[H1] Double Glazing UnitsManufacture & Supplier

High-quality double glazing sealed units for homes and businesses across London and the UK. Competitively priced, built to last, delivered in 5–7 working days.

Standard
Low-E
Toughened
Triple Glazed
Acoustic
Obscure

10-Year Guarantee

UK-Wide Delivery

5–7 Day Turnaround

Rated Excellent

Call for a Free Quotation
020 8058 4360

Email Us Anytime
[email protected]

[IMG: 10 Year Warranty]

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Brilliant service, saved us a fortune
Sealed units arrived within the week and were a perfect fit. Saved a fortune compared to ripping out the whole window. Can't fault them at all – would definitely use again.

Our go-to supplier for trade
We've been using these guys for about two years now on all our renovation jobs. Consistent quality, decent prices, and they actually deliver when they say they will. The argon Low-E units are spot on.

Misted units sorted in a day
Our Victorian terrace had misted windows all over the house. They replaced all 12 sealed units in one day and didn't touch the original timber frames. Massive difference in warmth – wish we'd done it sooner.

Helpful team, got the sizes sorted
I measured up wrong initially (my own fault) and gave them the wrong dimensions. Rang up, spoke to a really helpful bloke who walked me through measuring properly. Replacement units arrived bang on size. Top marks.

Great value for landlords
I've got six flats and needed sealed units across most of them. The trade pricing was genuinely competitive and they handled the whole lot without any fuss. Already booked them for another property.

Good product, delivery slightly slow
The sealed units themselves are excellent quality – no complaints there at all. Delivery took a day longer than expected which was a bit annoying as I had a fitter booked. But the end result is great.

Bay window looks brand new
Had a large bay window with a blown unit that was driving me mad. They came out, measured up, and fitted the replacement sealed unit within the week. Looks like a brand new window. Absolutely chuffed.

Whole house done, really pleased
We had every window in the house done – 14 units in total. They quoted quickly, delivered on time, and the fitter was neat and professional. Noticeably warmer already and our energy bill has dropped.

Conservatory units replaced perfectly
The conservatory roof panels had all misted up and it looked awful. Got all the sealed units swapped out and it's like having a brand new conservatory. Really happy with the result and the price was reasonable.

Reliable supplier, been using them for years
As a trade installer I need a supplier I can rely on and these lot haven't let me down yet. Good communication, quality products, and they understand the trade side of things. Wouldn't go anywhere else now.

Argon fill made a huge difference
Went for the argon-filled Low-E units on the recommendation of their team and the difference is night and day. The front bedroom used to be freezing in winter – now it's the warmest room in the house. Worth every penny.

Good product, website could be easier
The actual double glazing unit is excellent and fits perfectly. Only reason for four stars is the website could be a bit easier to navigate when choosing options. But the product and service? No complaints.

Bathroom window sorted quickly
Had a misted bathroom window that had been bugging me for months. Rang up on Monday, unit was delivered Friday, and my local handyman fitted it in 20 minutes. Crystal clear again. Dead easy process.

Perfect for our period property
We needed slimline units for our Edwardian semi because the rebates are quite narrow. They recommended the right spec and the units fit perfectly into the original frames. The house looks exactly as it should – just much warmer.

Use them on every job now
I'm a builder and I've tried a few different sealed unit suppliers over the years. These are the ones I stick with. Fair trade prices, they don't mess you about on lead times, and the quality is consistently good.

No more condensation!
Our kitchen window always had condensation running down it every morning. Got the sealed unit replaced with a Low-E argon unit and it's completely gone. Should have done it ages ago. Quick and painless service too.

Quick turnaround, impressed
Ordered on a Tuesday, units arrived the following Monday. For bespoke sizes that's really quick. Fitted them myself – straightforward job. Glass quality is excellent and the seal looks solid. Very impressed overall.

Great product, tracking could be better
Units are really good quality and the price was fair. Had to chase up the delivery tracking a couple of times as it wasn't updating. Once they arrived though, perfect fit and they look great. Would still recommend.

Road noise practically gone
We live on a busy main road and the old single-pane windows were useless. Upgraded to their acoustic sealed units and the difference is unbelievable. Can finally have a proper night's sleep. Money well spent.

10 windows done, faultless
Had 10 sealed units replaced across the front and back of the house. Every single one was the correct size, delivered on the day they said, and fitted without any problems. Really professional outfit from start to finish.

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[H2] Double Glazing Units Built to Your Exact Specification

We specialise in manufacturing and supplying high-performance double glazing units for both residential and commercial properties across the United Kingdom. Whether you need sealed units for acoustic insulation, energy-efficient Low-E glazing, or toughened safety glass, every unit is precision-built at our London facility to meet BS EN 1279 standards. From single replacements to large-scale trade orders, we supply double glazing sealed units nationwide with fast, reliable delivery direct to your door.

[IMG: Double glazing sealed units packaged for UK-wide delivery]

Supply Only

We manufacture and deliver double glazing sealed units directly to your door. Standard and bespoke sizes, trade and retail, with UK-wide delivery.
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[IMG: Professional installer fitting double glazing sealed units]

Supply & Install

Full service – we measure, manufacture, deliver, and install your new sealed units. All work carried out by our qualified installers.
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[IMG: Emergency broken double glazing unit replacement service]

Emergency Replacements

Fast response for smashed or damaged sealed units. We offer a board-up and replacement service to secure your property quickly.
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[H2] How It Works

From enquiry to installation in five simple steps – with expert guidance and fast turnaround at every stage.

1
[H3] Get in Touch

Call, email, or fill in our quick online form with your requirements.

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2
[H3] Free Quote

Receive a detailed, no-obligation quote within 2 hours.

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3
[H3] Manufacture

Precision-built to BS EN 1279 standards using Pilkington glass.

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4
[H3] UK Delivery

Securely packaged and delivered to your door nationwide.

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5
[H3] Installation

Professional fitting backed by our 10-year warranty.

[H2] Our Double Glazing Unit Types

We supply a comprehensive range of double glazed sealed units to suit every requirement and budget.

[IMG: Low-E low emissivity double glazing sealed unit]

Low-E Glass Units

Energy-efficient low emissivity glass that reduces heat loss whilst allowing natural light in. Ideal for meeting Building Regulations Part L.
View Details

[IMG: Toughened safety glass double glazing unit to BS EN 12150]

Toughened Glass Units

BS EN 12150 compliant toughened safety glass, required for doors, low-level windows, and areas near baths or showers under UK regulations.
View Details

[IMG: Acoustic sound-reducing double glazing sealed unit]

Acoustic Glass Units

Specialist sound-reducing sealed units using asymmetric glass configurations to significantly reduce external noise – perfect for busy roads.
View Details

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[H2] Gas-Filled Sealed Units for Superior Insulation

The gas fill inside your sealed unit makes a significant difference to thermal performance. Argon gas is the most popular choice for UK homes, offering around 34% better insulation than air-filled units at an affordable price.
For heritage properties requiring slimline units, krypton gas delivers excellent performance in narrower cavities. We also offer xenon gas for specialist commercial applications.
All our gas-filled units are manufactured to BS EN 1279-3 standards with a minimum 90% gas fill level, ensuring long-lasting thermal efficiency and compliance with Building Regulations Part L.
Compare Gas Fills
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[IMG: Argon gas filled double glazing sealed unit]

[H2] Areas We Cover

We supply and install double glazing units across London and the entire United Kingdom.

[H3] London

All boroughs covered
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[H3] Manchester

Greater Manchester
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[H3] Birmingham

West Midlands
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[H3] Leeds

West Yorkshire
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[H3] Bristol

South West England
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[H3] Liverpool

Merseyside
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[H3] Sheffield

South Yorkshire
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[H3] Nottingham

East Midlands
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[H2] Frequently Asked Questions

How much do double glazing units cost?

Double glazing unit prices vary depending on size, glass type, and gas fill. Standard sealed units start from around £70 for smaller sizes (500×500mm). Low-E and toughened options cost more. Visit our cost guide for a full UK price breakdown, or get a free quote for exact pricing on your requirements.

How long does delivery take?

Standard sealed units are typically manufactured and delivered within 5–7 working days. Bespoke sizes, specialist glass types, or specific gas fills may take 10–14 working days. We deliver across the entire United Kingdom, with free delivery on orders over £300.

Do you supply trade?

Yes. We offer trade accounts with competitive bulk pricing, dedicated account management, priority manufacturing, and credit terms (subject to approval). Whether you're a builder, window installer, or property developer, we have a trade solution that works for you.

What gas fill do you recommend?

For most UK homes, argon gas is the best balance of performance and cost, improving insulation by around 34% compared to air-filled units. Krypton gas is ideal for slimline units in heritage or listed buildings where a narrow cavity is required. Visit our gas fills page for a full comparison.

Can I just replace the glass, not the frame?

In most cases, yes. If your window frames are in good condition – whether uPVC, aluminium, or timber – we can replace just the sealed glass unit without touching the frame. This is far more cost-effective than a full window replacement and typically takes under an hour per unit.

Do you install nationwide?

We supply double glazing units nationwide across the UK. Our installation service covers London, the South East, Midlands, and most major UK cities. For areas outside our installation network, we offer supply-only with UK-wide delivery. Check our areas we cover page for details.

[H2] Need Double Glazing Units? Get Your Free Quote Today

Whether you need supply only or full installation, we've got you covered across London and the UK.

Get a Quote
Call Us Now

[H2] Latest from Our Blog

Expert guides, tips, and advice on double glazing units, replacement, and energy efficiency.

[IMG: Finding replacement double glazing units near your location in the UK]

10 April 2026 · 8 min read
[H3] Replacement Double Glazing Units Near Me – How to Find the Right Supplier

Looking for replacement double glazing units near you? Here's how to find a trusted local supplier and get the best price.
Read More

[IMG: How to choose a double glazing unit supplier in the UK]

8 April 2026 · 9 min read
[H3] Double Glazing Unit Suppliers – What to Look For

How to choose a reliable double glazing unit supplier in the UK, including accreditations, lead times, and key questions to ask.
Read More

[IMG: Guide to buying double glazing sealed units online in the UK]

5 April 2026 · 10 min read
[H3] Buying Double Glazing Sealed Units Online – The Complete UK Guide

Everything you need to know about ordering sealed units online, from measuring to delivery and quality checks.
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Home›Products
[H1] Double Glazing Unit Types

A comprehensive range of sealed units to suit every requirement – from standard units to specialist acoustic, fire-rated, and self-cleaning glass.

Every sealed unit we manufacture is built to BS EN 1279 standards with your choice of gas fill – argon, krypton, or xenon. All units available for supply only or supply and installation across the UK.

[IMG: Standard double glazed sealed unit with clear float glass]

Standard Double Glazed Units

Our most popular and cost-effective option. Standard double glazed sealed units feature two panes of clear float glass separated by a warm-edge spacer bar, with an air or argon gas fill for improved thermal insulation. Available in a wide range of standard and bespoke sizes, manufactured to BS EN 1279 standards. Ideal for straightforward replacements and new installations where specialist glass is not required.
Get a Quote

[IMG: Triple glazed sealed unit with three panes and two gas-filled cavities]

Triple Glazed Units

Superior thermal and acoustic performance with three panes of glass and two gas-filled cavities. Triple glazed units achieve significantly lower U-values than standard double glazing, making them the ideal choice for new builds, Passivhaus projects, and energy-efficient refurbishments aiming to exceed Building Regulations Part L requirements. Available with Low-E coatings and argon or krypton gas fills for maximum efficiency. BFRC energy rated.
Get a Quote

[IMG: Toughened safety glass double glazing unit to BS EN 12150]

Toughened Safety Glass Units

Manufactured to BS EN 12150 standards, our toughened safety glass is up to five times stronger than standard annealed glass. When broken, it shatters into small, relatively harmless granules rather than dangerous shards. Required under UK Building Regulations for critical locations including doors, side panels, low-level glazing (sill height below 800mm), and areas adjacent to baths or showers. Each pane carries a permanent BS EN 12150 kitemark stamp.
Get a Quote

[IMG: Low-E low emissivity double glazing sealed unit]

Low-E (Low Emissivity) Glass Units

Low-E glass features a microscopically thin metallic coating that reflects radiant heat back into the room whilst allowing natural light to pass through. See our guide to glass types for a detailed comparison, dramatically reducing heat loss. We offer two types: soft-coat Low-E, applied in a vacuum process after manufacture, delivers the best thermal performance and must be used within a sealed unit; hard-coat Low-E, applied during manufacture, is slightly less efficient but more durable. Low-E units help meet Building Regulations Part L and improve your property's BFRC energy rating.
Get a Quote

[IMG: Acoustic sound-reducing double glazing sealed unit]

Acoustic / Sound-Reducing Units

Specialist acoustic sealed units designed to significantly reduce external noise ingress – ideal for properties near busy roads, flight paths, railways, and urban centres. Acoustic units use asymmetric glass configurations (for example, 6mm outer pane and 4mm inner pane) to disrupt sound wave transmission more effectively than symmetric setups. Depending on the configuration, noise reduction of up to 40 dB or more is achievable. Can be combined with argon gas fill and Low-E coatings for thermal performance alongside acoustic benefits.
Get a Quote

[IMG: Obscure patterned privacy glass double glazing unit]

Obscure / Patterned Glass Units

Privacy glass double glazing units available in all popular UK obscure patterns, including Stippolyte, Cotswold, Arctic, Contora, Digital, Flemish, and more. Obscure glass is rated on a scale of 1 (least obscure) to 5 (most obscure), allowing you to choose the right level of privacy for bathrooms, front doors, side panels, stairwells, and WCs. All patterns can be combined with toughened safety glass where required by Building Regulations. Manufactured to BS EN 1279 standards.
Get a Quote

[IMG: Self-cleaning double glazing unit with photocatalytic coating]

Self-Cleaning Glass Units

Low-maintenance double glazing units featuring a dual-action photocatalytic and hydrophilic coating on the outer pane. UV light breaks down organic dirt on the glass surface (photocatalytic action), and when it rains, water sheets evenly across the surface and rinses the loosened residue away (hydrophilic action). We supply units featuring Pilkington Activ self-cleaning technology – the UK's most trusted self-cleaning glass brand. Perfect for hard-to-reach windows, conservatory roofs, and skylights.
Get a Quote

[IMG: Georgian bar decorative double glazing unit with internal glazing bars]

Georgian Bar / Leaded Units

Decorative double glazing units that replicate the traditional appearance of period and heritage properties. We offer three bar styles: internal Georgian bars housed within the sealed unit cavity for a clean, low-maintenance finish; external Georgian bars applied to the glass surface for a more authentic look; and duplex bars combining both internal and external bars for the most convincing traditional appearance. Available in white, gold, woodgrain, and custom colours to match your existing frames.
Get a Quote

[IMG: Solar control double glazing unit for conservatories and south-facing rooms]

Solar Control Glass Units

Solar control double glazing units reduce excessive solar heat gain whilst maintaining high levels of natural daylight – solving the problem of overheating in conservatories, south-facing rooms, orangeries, and large glazed extensions. The spectrally selective coating reflects a proportion of the sun's infrared energy, keeping interiors cooler in summer without the need for blinds or air conditioning. Can be combined with Low-E coatings to retain heat during winter, delivering year-round comfort and compliance with Building Regulations Part L.
Get a Quote

[IMG: Fire-rated double glazing unit compliant with UK Building Regulations Part B]

Fire-Rated Glass Units

Fire-rated double glazing units designed to comply with UK Building Regulations Part B (fire safety). Available in two classifications: integrity-only (E) units prevent the passage of flames and hot gases for a specified period; integrity-plus-insulation (EI) units also limit heat transfer through the glass, protecting occupants on the non-fire side. Essential for communal areas, escape routes, boundary glazing, and compartment walls in both residential and commercial buildings. All units are tested and certified to the relevant BS EN standards.
Get a Quote

[H2] Enhance Your Units with Gas Fills

The gas fill inside your sealed unit has a significant impact on thermal performance. Upgrading from air to argon gas improves insulation by around 34%, while krypton gas is ideal for slimline units in heritage properties where cavity width is limited.
All our double glazing unit types can be specified with your choice of gas fill. Visit our dedicated gas fill options page to compare argon, krypton, and xenon, and find out which is right for your project.
Compare Gas Fill Options

[IMG: Cross-section showing argon gas fill inside a double glazing sealed unit]

[H2] Frequently Asked Questions

What types of double glazing units do you supply?

We supply a comprehensive range including standard sealed units, triple glazed, toughened safety glass, Low-E (low emissivity), acoustic/sound-reducing, obscure/patterned, self-cleaning, Georgian bar/leaded, solar control, and fire-rated glass units. All manufactured to BS EN 1279 standards with your choice of gas fill.

What is the difference between soft-coat and hard-coat Low-E glass?

Soft-coat Low-E glass has a microscopically thin metallic coating applied after manufacture in a vacuum process. It offers superior thermal performance but must be used within a sealed unit. Hard-coat Low-E glass has the coating fused to the surface during manufacture, making it more durable and suitable for single glazing or exposed applications, but it is slightly less thermally efficient than soft-coat.

Do I need toughened glass in my double glazing?

Under UK Building Regulations, toughened or safety glass is required in critical locations including doors, side panels adjacent to doors, windows with a sill height below 800mm, and glazing near baths or showers. All our toughened glass complies with BS EN 12150 and carries a permanent kitemark stamp.

How much noise do acoustic double glazing units reduce?

Acoustic double glazing units can reduce external noise by up to 40 dB or more, depending on the glass configuration. Asymmetric setups – using different thickness panes such as 6mm outer and 4mm inner – disrupt sound waves more effectively than standard symmetric units. We can recommend the best configuration for your specific noise environment.

What gas fill options are available for sealed units?

We offer argon, krypton, and xenon gas fills. Argon is the most popular choice for UK homes, improving insulation by around 34% over air. Krypton suits slimline units in heritage properties, and xenon offers the highest performance for specialist applications. Visit our gas fills page for a full comparison.

Can I combine different glass types in one unit?

Yes. We can combine glass types within a single sealed unit – for example, toughened Low-E glass, acoustic obscure glass, or self-cleaning solar control glass. Contact us to discuss the best configuration for your requirements.

[H2] Not Sure Which Unit Type You Need? We Can Help

Tell us about your project and our team will recommend the right glass type, gas fill, and specification for your requirements. Free, no-obligation quotes across the UK.

Get a Free Quote
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Home›Services
[H1] Double Glazing Unit Services

From supply only to full installation, replacement, and emergency repairs – professional double glazing services across the UK.

[IMG: Double glazing sealed units packaged and ready for UK-wide delivery]

[H2] Supply Only Double Glazing Units

We manufacture and deliver high-quality sealed units directly to your door – no installation required. Whether you're a homeowner tackling a DIY project, a trade professional, or a property developer, our supply-only service gives you access to precision-built double glazing units at competitive prices.
We offer both standard and bespoke sizes, manufactured to BS EN 1279 standards. Choose from a wide range of glass types including Low-E, toughened, acoustic, and decorative options, with your choice of gas fill – argon, krypton, or xenon.
All units are securely packaged and delivered by specialist glass couriers across the entire United Kingdom. Free delivery on orders over £150.
Get a Supply Only Quote

Can I order double glazing units for delivery only?

Yes. We offer a full supply-only service for trade and retail customers. We manufacture your sealed units to your exact specifications and deliver them safely to your door anywhere in the UK. Free delivery on orders over £150.

What sizes can you supply?

We supply standard and bespoke sizes. Standard units start from 300×300mm up to 3000×2500mm. For non-standard shapes, arched tops, or unusual dimensions, contact us for a custom quote. Use our measuring guide to ensure accurate measurements.

Do you offer trade accounts for supply only?

Yes. We offer trade accounts with competitive bulk pricing, priority manufacturing, dedicated account management, and credit terms subject to approval. Ideal for builders, glaziers, and property developers.

[H2] Supply & Install Double Glazing Units

Our full-service option takes care of everything – from the initial survey and measurement through to manufacturing, delivery, and professional installation. You don't need to lift a finger.
All our installers are fully qualified and accredited, meaning their work is carried out to comply with Building Regulations Part L. You'll receive a compliance certificate upon completion, which is essential for property sales and insurance documentation.
We carry out a free, no-obligation home survey to take precise measurements and recommend the best glass configuration and gas fill for your property. Every unit is manufactured to BS EN 1279 standards and installed to the highest quality requirements set by the GGF (Glass and Glazing Federation).
Book a Free Survey

[IMG: Professional installer fitting a new double glazing sealed unit into a window frame]

Are your installers accredited?

Yes. All our installers are fully qualified and their work is carried out to comply with Building Regulations. You receive a compliance certificate upon completion, which is important for property sales and compliance.

Do you handle Building Regulations compliance?

Yes. As qualified installers, we self-certify compliance with Building Regulations Part L (energy efficiency). You won't need to involve your local council's building control department.

How long does a supply and install job take?

Most residential installations are completed within one day. Larger projects or properties with many units may take 2–3 days. We'll confirm the timeline during your free survey and quote.

[IMG: Glazier replacing a failed misted double glazing sealed unit in a uPVC window frame]

[H2] Replacement Double Glazing Units

If your sealed units have failed, misted up, or cracked, you almost certainly don't need to replace the entire window. We specialise in like-for-like replacement of the sealed glass unit – your existing uPVC, aluminium, or timber frames stay exactly where they are.
Failed sealed units – often visible as misted sealed units with condensation trapped between the panes – are caused by a breakdown of the perimeter seal. The only permanent fix is a full unit replacement, and that's exactly what we do. See our replacement guide for everything you need to know.
We match your existing unit specification, including glass type, spacer bar colour, and gas fill. Use our measuring guide to get accurate dimensions, or book a free home survey and we'll measure for you.
Get a Replacement Quote

Do I need to replace the whole window if the glass has failed?

No. In most cases, we can replace just the sealed glass unit without touching the frame. If your uPVC, aluminium, or timber frames are in good condition, replacing only the glass unit is far more cost-effective than a full window replacement.

What causes double glazing units to mist up?

Misting occurs when the perimeter seal of the sealed unit breaks down, allowing moisture to enter the gap between the panes. This is known as seal failure. The only permanent solution is to replace the sealed unit. Visit our misted sealed units page for more information.

Can you replace just one pane in a double glazed unit?

No. Double glazing is a sealed unit – both panes are bonded together with a spacer bar and sealed perimeter. If one pane is damaged, the entire sealed unit must be replaced to restore the thermal and acoustic performance.

[H2] Emergency / Broken Unit Replacement

Broken or smashed double glazing is a security risk and needs to be dealt with urgently. Our emergency response service is designed to secure your property fast – we attend, board up the opening, and arrange a replacement sealed unit as quickly as possible.
We carry board-up materials on every emergency call-out, so your property is made safe and weatherproof on the first visit. The replacement sealed unit is then manufactured to your exact specifications and fitted as soon as it's ready – typically within 5–7 working days.
Our emergency service covers accidental damage, break-ins, storm damage, and vandalism. We work with all major insurance providers and can supply documentation for your claim.
Call Us Now

[IMG: Emergency board-up and replacement of a broken double glazing unit]

How quickly can you respond to an emergency?

We aim to attend emergency call-outs within 2–4 hours in London and the South East. For other UK areas, we typically respond within 24 hours. We carry board-up materials to secure your property immediately.

Do you board up broken windows before fitting the replacement?

Yes. If the replacement unit needs to be manufactured, we will board up the opening with a secure timber or polycarbonate panel to keep your property safe and weatherproof until the new unit is ready.

Is there a call-out charge for emergencies?

There is no separate call-out charge. Our emergency pricing includes the board-up, assessment, and a quote for the replacement sealed unit. We are transparent with our pricing – no hidden fees.

[IMG: Commercial double glazing installation on a modern office building in the UK]

[H2] Commercial Double Glazing

We provide professional double glazing services for commercial properties across the UK – including schools, offices, retail units, and landlord portfolios. Whether you need a single unit replaced or a full multi-site glazing programme, we have the capacity and experience to deliver.
Our commercial service includes bulk pricing, dedicated project management, phased delivery schedules, and consolidated invoicing. All units are manufactured to BS EN 1279 standards, and our installations comply with Building Regulations Part L and relevant fire safety requirements.
We work with facilities managers, property management companies, housing associations, and local authorities. Get in touch to discuss your project requirements and receive a bespoke commercial quotation.
Request a Commercial Quote

Do you offer double glazing for commercial properties?

Yes. We work with schools, offices, retail units, and landlord portfolios across the UK. We offer bulk pricing, project management, and can handle large-scale replacements and new installations.

Can you manage a multi-site glazing project?

Yes. We have experience managing multi-site commercial projects across the UK. We provide a dedicated project manager, phased delivery schedules, and consolidated invoicing for landlord and property management portfolios.

Do your commercial units meet Building Regulations?

All our sealed units are manufactured to BS EN 1279 standards and comply with Building Regulations Part L. We also supply units that meet Document E (acoustic) and Document N (safety) requirements as needed.

[H2] Need Double Glazing Units? Get Your Free Quote Today

Whether you need supply only, full installation, or an emergency replacement, we've got you covered across the UK.

Get a Quote
Call Us Now

Home›Gas Fills
[H1] Gas-Filled Double Glazing Units

How argon, krypton, and xenon gas fills affect thermal performance, energy ratings, and heating costs.

[H2] Why Gas Fill Matters in Double Glazing

Every double glazing sealed unit consists of two (or three) panes of glass separated by a cavity. What fills that cavity has a direct and measurable impact on how well the unit insulates your home. The principle is straightforward: gases that are denser and less conductive than ordinary air slow the transfer of heat from the warm interior pane to the cold exterior pane more effectively.
In a standard air-filled sealed unit, convection currents form inside the cavity as warm air rises on the interior side and falls on the exterior side, creating a loop that transfers heat outwards. By replacing air with a heavier, less conductive noble gas – such as argon, krypton, or xenon – these convection currents are suppressed, heat transfer is reduced, and the overall U-value of the unit drops significantly.
A lower U-value means better insulation. For context, Building Regulations Part L in England currently requires replacement windows to achieve a whole-window U-value of 1.4 W/m²K or lower. The gas fill inside your sealed unit is one of the easiest and most cost-effective ways to meet and exceed this standard.
Gas-filled units also contribute to a higher BFRC (British Fenestration Rating Council) energy rating – the A++ to E scale you'll see on window energy labels throughout the UK. The better the gas fill, the higher the rating, and the greater the energy savings over the lifetime of the unit.
In this guide, we'll walk through each gas option in detail – including argon, krypton, xenon, and standard air – so you can understand the differences in thermal performance, cost, cavity requirements, and best-use scenarios. Whether you're replacing misted units in a semi-detached house or specifying glazing for a listed building, the right gas fill choice can make a real difference to comfort and running costs.

[H2] Argon Gas – The UK's Most Popular Choice

Argon is by far the most widely used gas fill in UK double glazing. It accounts for the vast majority of gas-filled sealed units manufactured in Britain, and for good reason: it offers an excellent balance of thermal performance, availability, and cost.
With a thermal conductivity of just 0.016 W/mK – roughly 34% lower than air (0.025 W/mK) – argon significantly reduces heat transfer across the cavity. In practical terms, this means a standard 4-16-4 sealed unit (4mm glass, 16mm cavity, 4mm glass) filled with argon will typically achieve a centre-pane U-value of around 1.1 W/m²K when combined with a low-emissivity (Low-E) coating. The same unit filled with air would sit at approximately 1.4–1.5 W/m²K.
Argon performs optimally in a 16mm cavity. At this width, the gas provides maximum resistance to convective heat transfer. Narrower cavities (below 12mm) do not allow argon to perform at its best, as the gas movement is constrained before the benefit of reduced convection is fully realised. Wider cavities (above 20mm) can actually worsen performance, as the larger space allows convection currents to re-establish.
[H3] BS EN 1279-3 Certification

All reputable UK manufacturers, including ourselves, produce argon-filled units to BS EN 1279-3 – the European standard governing gas fill in insulating glass units. This standard requires a minimum 90% gas fill concentration at the point of manufacture, verified through regular third-party testing. The standard also prescribes gas retention rates over the expected service life of the unit, ensuring the gas concentration remains effective for 20 years or more.
[H3] Cost Considerations

Argon is abundantly available – it makes up roughly 0.93% of the Earth's atmosphere and is a by-product of oxygen and nitrogen production. This abundance keeps the cost low. Upgrading from an air-filled to an argon-filled sealed unit typically adds just £10–£30 per unit, making it one of the most cost-effective thermal upgrades available in glazing. For a full breakdown of pricing, visit our cost guide.
[H3] Who Should Choose Argon?

Argon is the right choice for the overwhelming majority of UK homeowners, landlords, and trade professionals. It is ideal for standard replacement sealed units, new-build glazing, and any application where a standard 16mm cavity width is feasible. If you're replacing misted units or upgrading from older air-filled glazing, argon should be your default choice – the performance improvement is substantial, and the cost premium is negligible.

[IMG: Argon gas filled double glazing unit with 16mm cavity for optimal thermal performance]

Argon gas filled sealed unit with a 16mm cavity – the UK's standard for energy-efficient glazing.

[H2] Krypton Gas – Superior Performance in Slimline Units

Krypton is a denser, rarer noble gas that offers significantly better thermal insulation than argon. With a thermal conductivity of 0.0095 W/mK – approximately 40% lower than argon and 62% lower than air – krypton is the preferred gas fill when you need maximum thermal performance in a restricted space.
Unlike argon, which requires a 16mm cavity to perform well, krypton achieves its optimal performance in a 10–12mm cavity. This makes it particularly valuable in situations where a standard-width sealed unit cannot be accommodated – most notably in heritage and listed buildings where the original window profiles are narrow, and planning regulations restrict how much the glazing depth can be increased.
[H3] When to Choose Krypton Over Argon

Krypton should be considered when:

Heritage or listed buildings – where Conservation Officers require slimline double glazing units that replicate the appearance of original single-glazed windows.
Slim-profile window systems – such as steel-framed windows or heritage aluminium systems with narrow rebates that cannot accommodate a 16mm+ cavity.
Triple glazing with limited overall depth – where two gas-filled cavities must fit within a tight overall unit thickness.
Maximum U-value performance – where Building Regulations or project specifications demand the lowest possible U-values and the additional cost is justified.

[H3] Cost and Availability

Krypton is significantly rarer than argon in the atmosphere (roughly 1 part per million compared to argon's 9,340 parts per million), which makes it 3–5 times more expensive as a gas fill. A krypton-filled sealed unit might add £50–£120 per unit over an air-filled equivalent, depending on size. Despite the higher cost, krypton remains the only practical solution for slimline glazing that needs to meet modern thermal standards.
[H3] Performance Data

A typical 4-12-4 sealed unit with krypton fill and a Low-E coating can achieve a centre-pane U-value of around 1.0 W/m²K – comparable to, or better than, an argon-filled 4-16-4 unit. This is remarkable considering the cavity is 25% narrower, and it underlines why krypton is the go-to gas for applications where space is at a premium.

[IMG: Krypton gas filled slimline double glazing unit installed in a heritage listed building]

Krypton gas units are ideal for heritage properties where slimline glazing profiles are required.

[H2] Xenon Gas – The Ultimate in Thermal Insulation

Xenon is the densest and most thermally efficient noble gas used in insulating glass units. With a thermal conductivity of just 0.0054 W/mK – almost five times lower than air and roughly a third of argon's figure – xenon offers the absolute best performance available in gas-filled glazing.
Xenon performs optimally in an 8–10mm cavity, making it theoretically ideal for ultra-slim glazing profiles. A 4-8-4 unit filled with xenon and fitted with a Low-E coating can achieve a centre-pane U-value below 0.9 W/m²K – a level of insulation that air and argon simply cannot match in such a compact profile.
[H3] Why Xenon Is Rarely Used Domestically

Despite its outstanding thermal properties, xenon is rarely specified for UK domestic glazing for one primary reason: cost. Xenon is extremely rare in the atmosphere (approximately 0.087 parts per million), making it one of the most expensive noble gases available. The cost of xenon fill can be 10–20 times higher than argon, adding £160–£400+ per sealed unit depending on size.
For most homeowners, the additional thermal benefit over krypton does not justify this premium. The law of diminishing returns applies firmly: moving from air to argon delivers a transformative improvement at minimal cost, moving from argon to krypton provides a meaningful further step for specific applications, but moving from krypton to xenon yields a relatively modest additional gain at a disproportionately high price.
[H3] Commercial and Specialist Applications

Xenon finds its niche in specialist commercial applications where every fraction of a U-value point matters – for example, high-performance curtain walling on BREEAM Excellent-rated commercial buildings, passive house (Passivhaus) certified projects, or research facilities with extremely stringent environmental control requirements.
If you are working on a commercial project with demanding thermal specifications, our team can advise on whether xenon fill is the right option. Get in touch to discuss your requirements.

[IMG: Xenon gas filled insulating glass unit used in a high-performance commercial curtain wall system]

Xenon gas is primarily used in high-specification commercial projects where the highest thermal performance is required.

[H2] Air-Filled Units – The Standard Baseline

Before gas-filled units became the industry norm, all double glazing units were filled with standard dehydrated air. Air has a thermal conductivity of 0.025 W/mK – higher than any of the noble gas alternatives – which means it offers the lowest level of insulation in a sealed unit.
Air-filled sealed units are still manufactured and have their place. They are the cheapest option available, and for non-heated or low-priority spaces, the reduced thermal performance is perfectly acceptable. Common applications include:

Garages and detached outbuildings – where the space is unheated or only occasionally used.
Sheds, workshops, and garden rooms – especially where the structure itself has poor insulation, making gas-filled glazing a marginal improvement.
Temporary or short-term installations – where the budget does not justify the premium of gas fill.
Internal partitions – where thermal insulation between the two sides is not required.

[H3] Performance Comparison

A standard 4-16-4 sealed unit with air fill and no Low-E coating will typically achieve a centre-pane U-value of around 2.7–2.8 W/m²K. Add a Low-E coating and the figure improves to approximately 1.4–1.5 W/m²K, but this still falls short of Building Regulations Part L requirements for replacement windows in habitable rooms without further upgrades.
For any heated living space in the UK, we strongly recommend upgrading to at least argon gas fill. The cost difference is minimal, and the energy savings over the life of the unit far exceed the initial premium. View our full range of unit types to find the right specification for your project.

[IMG: Standard air-filled double glazing sealed unit suitable for garages and outbuildings]

Air-filled sealed units remain a budget-friendly option for outbuildings and unheated spaces.

[H2] Gas Fill Comparison Table

A side-by-side comparison of the four gas fill options available for double glazing sealed units, including thermal conductivity, optimal cavity width, relative cost, and best-use scenarios.

Gas Type
Thermal Conductivity (W/mK)
Optimal Cavity (mm)
Relative Cost
Best Use
U-Value Improvement vs Air

Air
0.025
16
£ (lowest)
Garages, outbuildings, internal partitions
Baseline

Argon
0.016
16
££ (low premium)
Standard domestic & commercial glazing
~34% improvement

Krypton
0.0095
10–12
£££ (3–5× argon)
Heritage buildings, slim-profile units
~62% improvement

Xenon
0.0054
8–10
££££ (10–20× argon)
Specialist commercial, Passivhaus
~78% improvement

Note: U-value improvements are approximate centre-pane figures and will vary depending on glass type, Low-E coating, spacer bar, and overall unit configuration. All gas fills should be specified to BS EN 1279-3 with a minimum 90% fill concentration.

[H2] BFRC Energy Ratings & Building Regulations Part L

The British Fenestration Rating Council (BFRC) operates the UK's national window energy rating scheme. Every window sold in the UK can be rated on a scale from A++ (best) to E (worst), based on three factors: the U-value (heat loss), the solar heat gain (free energy from sunlight), and air leakage through the frame.
The gas fill inside a sealed unit directly influences the U-value component of this rating. Switching from air to argon alone can shift a window's energy rating by one or two bands – for example, from a C rating to an A rating. This makes gas fill one of the most impactful and cost-effective upgrades when targeting a higher BFRC rating.
[H3] Part L Compliance

Building Regulations Part L (Conservation of fuel and power) sets the minimum thermal performance standards for windows in England. As of the current regulations, replacement windows in existing dwellings must achieve either:

A whole-window U-value of 1.4 W/m²K or lower, or
A BFRC energy rating of Band C or above.

In practice, achieving 1.4 W/m²K consistently requires a Low-E coated, gas-filled sealed unit. An air-filled unit with Low-E coating may just scrape through on a small window, but argon fill provides a comfortable margin of compliance and is essentially the minimum standard for responsible specification.
[H3] Reaching A++ Ratings

To achieve the highest A++ energy ratings in the BFRC scheme, you'll typically need a combination of:

High-performance Low-E glass (such as Planitherm Total+ or Pilkington Energikare)
Argon or krypton gas fill at 90%+ concentration
Warm-edge spacer bars (e.g., Thermobar, Swisspacer, or Super Spacer)
A thermally efficient frame system (multi-chamber uPVC, timber, or thermally broken aluminium)

Gas fill is therefore a critical component but works best as part of a holistic approach to window energy performance. Our team can advise on the right combination of glass, gas, and spacer for your required rating – get a free quote to find out more.

[IMG: BFRC window energy rating label showing an A-rated double glazing unit with argon gas fill]

A BFRC energy label – ga

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[H2] Find Double Glazing Units in Your Area

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[H2] Why Choose Double Glazing Units?

No matter where you are in the UK, you receive the same high standard of service. Every sealed unit we manufacture is built to BS EN 1279 standards and backed by a comprehensive guarantee. All installations are carried out to comply with Building Regulations.
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Whether you need supply only, supply and install, or emergency replacement, we deliver competitively priced units in 5–7 working days. Browse our full product range or request a free quote today.

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Don't see your area listed above? We supply double glazing units to every corner of the United Kingdom, including Scotland, Wales, and Northern Ireland. Our supply-only service includes fully insured UK-wide delivery, with most orders dispatched within 5–7 working days.
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