Understand double glazing before you buy it

Double glazing explained in 60 seconds

Double glazing is a sealed window unit made from two panes of glass with a gap between them, filled with air or an inert gas such as argon. That trapped layer slows the movement of heat and sound, so a well-specified unit keeps warmth in during winter, reduces outside noise, and cuts the condensation that forms on cold single-glazed panes. The frame that holds the unit — uPVC, aluminium or timber — matters just as much as the glass itself.

Almost every replacement window fitted in Britain today is at least double glazed, and the price you are quoted reflects a handful of choices: the frame material, the glass specification, the window style, and the standard of installation. Understanding those four levers is the whole job of this guide. Get them straight and you can read any quote on its merits rather than on the salesperson's script.

For the full walk-through, start with our double glazing buyer's guide, or read double glazing explained in more depth.

The three choices that shape your quote

Before you speak to an installer, it helps to have a view on each of these. Each links to a fuller guide.

• Frame materials

  uPVC, aluminium and timber compared on cost, looks, lifespan and upkeep. Compare frame materials.

• Glass & units

  Low-E coatings, argon fill, triple glazing, acoustic and toughened glass. Explore glass types.

• Window styles

  Casement, sash, tilt-and-turn, bay and more — matched to UK homes. See window styles.

Building regs & standards, in brief

How to buy with confidence in the UK

You do not need a named brand to buy well — you need a short checklist and quotes you can compare like for like. Look for these signals in any installer you consider:

• Registered with a Competent Person Scheme such as FENSA or CERTASS, so the work is certified and notified to building control.
• An insurance-backed guarantee on the installation, so cover survives if the fitter later ceases trading.
• Deposit protection in place before you pay anything up front.
• A written, itemised quote after a proper home survey — not a price agreed on the doorstep.

How getting quotes works

1. Tell us about your home

   Answer a couple of quick questions and share where you are — it takes under a minute.

2. Get matched locally

   We connect you with vetted, accredited installers who cover your area.

3. Compare free quotes

   Receive free, no-obligation quotes and choose in your own time, with no pressure.

Want to see installer feedback first? You can see verified installer reviews before you request quotes.

The full double glazing guide

Nine focused guides covering everything from glass specs to when it is time to replace.

• Buyer's guideYour start-to-finish route through the whole decision.
• Double glazing explainedWhat it is and how a sealed unit actually works.
• Frame materials compareduPVC vs aluminium vs timber, side by side.
• Glass typesLow-E, argon, triple, acoustic and toughened glass.
• UK window stylesCasement, sash, tilt-and-turn, bay and beyond.
• Building regulationsWhat the rules require for replacement windows.
• FENSA & CERTASSCertification schemes and why they matter.
• How long it lastsRealistic lifespans for units, frames and seals.
• When to replaceThe tell-tale signs it is time for new windows.
• Getting quotesHow to gather and compare UK quotes properly.

Common questions