Double Glazing Cost Calculator

How to Use the Double Glazing Cost Calculator

1. Choose a mode. "New windows" prices complete replacement windows. "Replace glass units" prices new sealed units for frames that are still in good condition.
2. Add your windows. For each group, enter how many, the style (casement, tilt and turn, flush casement, sash or bay), the frame material and the size.
3. Choose double or triple glazing.
4. Add scaffolding if any upstairs windows can't be reached safely from ladders.
5. Read the result: a fitted price range for each group, a total, and an average price per window.

In USA mode, the same calculator gives double-pane replacement window prices in dollars.

How Much Does Double Glazing Cost in 2026?

For a typical medium-sized casement window, fitted prices are roughly:

These figures combine published per-window prices with typical fitting costs. For a whole job, expect extras for removing the old windows (£200–£500 for 8–10 windows), waste disposal (£50–£150) and, where needed, scaffolding (up to about £500). It's sensible to keep 10–20% aside for surprises such as rotten lintels or damaged reveals.

Cost for a whole house

Published whole-house figures vary a lot between sources and installers, which is why itemising your own windows in the calculator gives a better budget.

uPVC vs Aluminium vs Timber: Which Frame?

• uPVC is the most popular choice in UK homes. It's the cheapest, doesn't need painting, and insulates well. Modern uPVC comes in woodgrain foils and colours such as anthracite grey, but bulkier frames can look out of place on period homes.
• Aluminium frames are strong enough to be very slim, so you get more glass and a modern look. Thermally broken aluminium performs well, and it's very durable. It costs roughly 25–30% more than uPVC.
• Timber suits period properties and is often required in conservation areas. Factory-finished engineered timber can last decades but needs repainting every several years. It's the most expensive option, often more than double uPVC.
• Composite (timber inside, aluminium outside) gives a warm interior look with a low-maintenance exterior, at a price between aluminium and timber.

Prices by Window Style

The calculator adjusts the casement price for other styles:

Sizes: small windows (up to about 0.6 m², such as bathroom windows) are about 25% cheaper than medium (0.6–1.5 m²), and large windows (1.5–2.5 m²) about 35% dearer. These style and size factors are BuildCalc's estimating model, built from the published ranges, so use the result as a budget.

Timber sash windows are the most expensive common choice: roughly £2,770–£3,480 each for a medium size. A uPVC sash costs about £990–£1,390.

Double vs Triple Glazing

Triple glazing adds a third pane of glass. It lowers heat loss and noise further, but usually adds 10–20% to the cost and makes windows heavier.

• Choose double glazing for most UK homes. Modern A-rated double glazing with a low-E coating, argon gas and warm-edge spacers performs well.
• Consider triple glazing for very exposed or noisy locations, north-facing rooms, or deep energy retrofits and heat pump homes.

If the windows themselves are in good condition and you want to cut noise or drafts cheaply, secondary glazing (a second slim window fitted inside the existing one) is another option. It's often the only one allowed in listed buildings.

Energy Ratings, U-values and Building Regulations

Replacement windows in England and Wales must meet the Building Regulations. Under Part L, a replacement window needs a U-value of 1.4 W/m²K or better (lower means less heat loss), or an equivalent Window Energy Rating. Many windows sold today are A-rated or better on the Window Energy Rating scale.

You don't need to apply to building control yourself if you use an installer registered with a competent person scheme such as FENSA or CERTASS. They self-certify the work and you receive a certificate. Keep it: your buyer's solicitor will ask for it when you sell. If your installer isn't registered, you'll need to apply to building control before work starts.

Planning permission isn't usually needed for like-for-like replacement windows, but check first if:

• Your home is a listed building (you'll need listed building consent)
• You're in a conservation area or an area with an Article 4 direction
• You're changing the size of openings or adding new ones, especially on upper side walls

Windows also have to meet rules on safety glass in low areas, ventilation (trickle vents may be needed when replacing), and fire escape openings from upstairs rooms.

Replacing Misted Glass Units Only

If the glass is misty or foggy between the panes, the sealed unit has failed but the frame may be fine. Replacing just the sealed unit costs far less than a new window, typically around £100–£250 per unit depending on size and glass type. Choose "Replace glass units" in the calculator to price this.

New sealed units are worth it when frames, hinges and seals are sound and you're happy with the style. If the frames are draughty, warped or more than about 20–25 years old, a full replacement is usually better value.

Grants and Funding

Window grants are limited in 2026:

• Warm Homes: Local Grant (England, 2025–2028): up to £16,600 for energy efficiency work, which can include double or triple glazing. It's aimed at lower-income households in homes rated EPC D to G, and is run through participating councils.
• ECO4: runs until the end of 2026 with limited funding; windows are only funded as part of a wider package with insulation.
• Scotland: interest-free loans for replacing single glazing; Wales: home improvement loans through councils.

Schemes change often, so check with your council or the official government grants checker before you sign anything.

Double-Pane Windows in the USA

In the USA, "double glazing" is usually called double-pane or insulated glass. A standard vinyl double-pane replacement window typically costs about $800–$1,600 installed, and fiberglass or wood about $1,100–$2,200. For full US pricing by window type, use the Window Replacement Cost Calculator. The federal 25C tax credit for windows ended on December 31, 2025.

How to Get a Good Deal

1. Get at least three quotes for the same specification, and check what each includes.
2. Check registration with FENSA or CERTASS, and ask about an insurance-backed guarantee.
3. Don't pay a large deposit. Avoid high-pressure "today only" discounts.
4. Compare like with like: frame material, glass (A-rated, low-E, argon, toughened where needed), hardware and colour.
5. Think about the whole house. Improving loft insulation often saves more per pound than windows: see the Insulation Calculator.

Frequently Asked Questions