Double glazing is one of the most impactful home improvements you can make – cutting heat loss through windows by up to 50% and reducing outside noise. But prices vary wildly depending on the type of windows, your home’s size, and which company you use. Here’s what you should actually expect to pay in 2025.
Double Glazing Costs by Window Type
| Window Style | uPVC | Aluminium | Timber |
|---|---|---|---|
| Casement (standard) | £300 – £500 | £500 – £800 | £700 – £1,200 |
| Sash (sliding) | £500 – £800 | £800 – £1,200 | £1,000 – £1,800 |
| Bay window (3-panel) | £1,200 – £2,000 | £1,800 – £3,000 | £2,500 – £4,500 |
| Tilt & turn | £350 – £600 | £600 – £900 | £800 – £1,300 |
| French doors (pair) | £800 – £1,200 | £1,200 – £2,000 | £1,500 – £2,800 |
| Bi-fold doors (3-panel) | £2,500 – £4,000 | £3,500 – £6,000 | £5,000 – £8,000 |
Prices include supply and professional installation. VAT at 20% for replacement windows.
Full House Costs by Property Type
| Property | Windows | uPVC Cost | Aluminium Cost |
|---|---|---|---|
| 1-bed flat | 3–5 | £1,500 – £2,500 | £2,500 – £4,000 |
| 2-bed terrace | 6–8 | £2,500 – £4,500 | £4,500 – £7,000 |
| 3-bed semi | 8–12 | £4,000 – £7,000 | £7,000 – £12,000 |
| 4-bed detached | 12–18 | £6,000 – £9,000 | £9,000 – £15,000 |
uPVC vs Aluminium vs Timber
✅ uPVC (Best Value)
- Cheapest option by far
- Low maintenance – just wipe clean
- Good thermal performance
- Wide range of colours/finishes
- Lifespan: 20–25 years
⚠️ uPVC Downsides
- Can look plasticky on period properties
- Frames slightly thicker than aluminium
- Can discolour over time (white)
- Not suitable for conservation areas
What Affects the Price?
| Factor | Impact on Cost |
|---|---|
| Window size | Larger windows cost more – a small bathroom window vs a lounge bay can differ by £1,000+ |
| Style (casement vs sash) | Sash windows cost 40–60% more than casement |
| Frame material | Aluminium costs 50–70% more than uPVC; timber costs 100–150% more |
| Glass spec | Triple glazing adds 20–30% vs standard double. Low-E coatings add £20–£40 per window |
| Access difficulty | Upper floors, scaffolding needed, narrow access adds £200–£800 |
| Location | London/South East: 15–25% higher than national average |
Double vs Triple Glazing
| Feature | Double Glazing | Triple Glazing |
|---|---|---|
| U-value (lower = better) | 1.2–1.4 W/m²K | 0.7–0.9 W/m²K |
| Cost premium | Baseline | +20–30% |
| Noise reduction | Good (30–35dB) | Excellent (35–40dB) |
| Best for | Most UK homes | Exposed/noisy locations, passive houses |
| Payback on extra cost | N/A | 15–25 years (energy savings alone) |
How to Save Money
- Get 3+ quotes – prices from national companies can be 40–60% higher than local installers for the same product
- Avoid “buy now” pressure – any company offering massive same-day discounts is inflating the original price
- Do the whole house at once – bulk discounts of 10–20% are common
- Check for grants – ECO4 can fund double glazing for eligible low-income households
- Consider timing – autumn/winter quotes are often 10–15% cheaper (lower demand)
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Energy Savings & Payback
| Scenario | Annual Saving | Payback Period |
|---|---|---|
| Replacing single glazing (full house) | £200 – £350 | 12–20 years |
| Replacing old double glazing (20+ years) | £100 – £180 | 20–35 years |
| Adding secondary glazing | £100 – £200 | 5–10 years |
Frequently Asked Questions
Do I need planning permission for double glazing?
In most cases, no. Replacement windows are permitted development. However, if you live in a conservation area or listed building, you may need planning approval. Building regulations approval (FENSA or Local Authority) is always required and should be arranged by your installer.
How long does installation take?
A full house (10–12 windows) typically takes 2–3 days. Each individual window takes 1–2 hours to swap. Your home will be secure and weatherproof at the end of each day.
What’s the difference between A-rated and C-rated windows?
The Window Energy Rating (WER) runs from A++ (best) to E (worst). A-rated windows have better insulation, Low-E coatings, and argon gas fill. The energy saving difference between A and C is modest (£15–£30/year) but A-rated windows have better sound insulation and condensation resistance.
Learn More About Double Glazing
Our complete guide covers frame types, glass options, and getting the best deal.