Buying double glazing

Buying double glazing goes in a set order: decide what you want, get three or more quotes, compare them on the same specification, then check the survey, contract and certificate before you pay the balance. For a typical three-bedroom semi in uPVC, expect around £5,000, with most people paying between £3,500 and £8,000. Each step has its own guide, linked at the top of this page.

Step 1: decide what you need

Start with the house, not the brochure. Count the windows and doors you want to replace, and note which ones open and which way. Then choose the material and the style.

• Material. uPVC is the cheapest and needs no upkeep. Aluminium gives slimmer frames. Timber suits period houses and conservation areas.
• Style. Casements suit most post-war homes, sash windows suit Georgian, Victorian and Edwardian houses, and bay windows replace like for like.
• Glass. A-rated double glazing is enough for most homes. Triple glazing helps in noisy or cold rooms.
• Doors. If the front door is tired, a composite door at the same time saves a second visit.

Before you settle on a style, check whether you need planning permission for windows. Most houses don’t, but listed buildings, flats and conservation areas often do.

Step 2: get double glazing quotes from several installers

Get at least three quotes. Prices for the same house routinely differ by thousands, often because one firm has left something out or quoted a different specification. Local installers registered with FENSA or CERTASS usually quote well below the national brands for comparable windows.

Our guide to choosing a double glazing installer lists what to check, from registration to the guarantee. When you’re ready, get quotes from up to four local firms.

Step 3: compare like with like

A cheap quote that leaves out removal, making good or certification isn’t cheap. Put every quote on the same basis:

• the number, size and style of each window;
• the frame profile, colour and glass specification, including energy rating;
• removal of the old windows, waste and making good inside;
• FENSA or CERTASS certification, and the guarantee;
• VAT, because a quote without it looks much cheaper than one with it.

The compare quotes tool puts up to three quotes side by side, and the quote checker tells you whether a price is reasonable for your area.

Step 4: the survey and the contract

Once you choose a firm, a surveyor measures every opening precisely before anything is made. That is your chance to agree the details in writing: which way each window opens, where the trickle vents go, which panes need toughened glass, and what happens if they find rot or a weak lintel. How double glazing installation works walks through the whole process.

Read the contract before you sign it. Check the deposit, when the balance falls due, the cancellation terms and the guarantee. Made-to-measure windows can lose the usual right to cancel once ordered, so know your rights before signing anything at the kitchen table.

Colours, glass and hardware

Once the material and style are settled, the choices that change the look most are the colour, the glass and the handles. White is the base price, and coloured or woodgrain finishes cost more, especially when the colour goes on both sides. Obscure glass suits bathrooms and front doors, and toughened glass is required in doors and low panes. Choose handles that match across the house, and ask for key-locking handles on ground-floor windows. On a period house, glazing bars and a traditional sill make the biggest difference to how the new windows look. Ask to see samples of the actual colour and handle before you sign, because brochures rarely match the real thing.

Doors at the same time

If the front, back or garden doors are due for replacement, doing them with the windows saves a second survey and a second visit, and the colours will match. A composite door is the usual front-door choice; for the garden, compare French doors, sliding patio doors and bifold doors. Buying double glazing for the whole house in one go also gives you a stronger hand when you negotiate.

Step 5: paying

Pay a modest deposit and the balance only when the job is finished and you’re happy. Paying part of the cost by credit card gives you extra protection if something goes wrong. If you’re spreading the cost, compare the total repayable, not just the monthly figure; see paying for double glazing.

Step 6: fitting day and afterwards

Most houses take one to three days. The fitters take out each old window, fit the new one, seal it and make good, usually one room at a time so the house is never open for long. Before they leave, open and lock every window, check every seal, and make sure the frames are clean and undamaged.

Afterwards, you should receive two documents: the FENSA certificate or equivalent, which you’ll need when you sell, and the guarantee, ideally insurance-backed. File both with your house deeds.

Common mistakes when buying double glazing

• Signing on the first visit. “Today only” discounts are a sales technique. A genuine price will still be there next week.
• Comparing headline prices. Specifications differ more than prices do.
• Ignoring the frame. Glass gets the attention, but the frame decides how the window looks and how long it lasts.
• Forgetting ventilation. New windows seal tightly. Trickle vents prevent condensation.
• Paying in full up front. Never pay the balance before the work is finished.

How long it takes

From first quote to fitted windows usually takes a few weeks to a couple of months. The survey comes within a week or two of accepting a quote, and manufacture takes several weeks. Timber and aluminium often take longer than uPVC. The certificate arrives some weeks after fitting.

Prices at a glance

Product	Typical price
uPVC windows, 3-bed semi	£5,000
Aluminium windows, 3-bed semi	£8,500
Timber windows, 3-bed semi	£12,500
Composite front door	£1,400

Prices include VAT; see double glazing prices for every product and region. The guides at the top of this page go deeper into each step, and our guide to double glazing regulations covers the rules the work has to meet. The Planning Portal sets out the official position for England.