Ofgem data shows homeowners spend up to £1,200 annually on heat loss through single-glazed timber casement windows
If your home has single-glazed timber casement windows, you could be losing a significant amount of heat each year. Ofgem data for 2026 shows that a typical three-bed semi-detached house with single-glazed timber casement windows can lose up to £1,200 annually in heat through those windows alone (Ofgem, 2026).
Timber casement windows cost £800-£1,200 per window in 2026. Single-glazed versions can lose up to £1,200 annually in heat (Ofgem). Upgrading to double-glazed cuts heat loss by 50-60%. Compare installer quotes to find the best deal.
- Timber casement windows cost £800-£1,200 per window supplied and fitted (2026).
- Single-glazed timber windows lose up to £1,200 annually in heat per Ofgem data.
- Double-glazed timber casement windows cut heat loss by 50-60% (Energy Saving Trust).
- uPVC equivalents cost £400-£700 per window, 40-50% less than timber.
- Check local planning authority before ordering timber windows for listed buildings.
- Ofgem data shows homeowners spend up to £1,200 annually on heat loss through single-glazed timber casement windows
- The 2026 cost of buying and installing timber casement windows
- Annual energy savings from switching to double-glazed timber casement windows
- Quick numbers timber casement windows versus uPVC – cost, lifespan, and energy performance
- Timber casement windows have a longer lifespan but require more care
- The direct answer timber casement windows cost more upfront but offer lower lifetime carbon impact
- How to verify a timber casement window installer is certified
- Annual maintenance cost for timber casement windows
Single-glazed timber casement windows have a U-value of approximately 4.8 to 5.4 W/m²K. U-value measures how easily heat passes through a material. Lower numbers mean better insulation. Upgrading to double-glazed timber casement windows reduces heat loss by 50 to 60 percent (Energy Saving Trust, 2026).
This article compares the 2026 costs, energy savings, and maintenance for timber casement windows versus uPVC alternatives. It covers buying costs, running costs, lifespan, and how to check an installer is certified.
The 2026 cost of buying and installing timber casement windows
Timber casement windows cost more upfront than uPVC. The average cost per timber casement window, supplied and fitted, is £800 to £1,200 for a standard 1.2 metre by 1.2 metre opening (MCS, 2026). The uPVC equivalent costs £400 to £700 per window (Energy Saving Trust, 2026).
Installation labour accounts for 30 to 40 percent of the total cost. Timber casement windows typically require a 10 to 15 percent premium for heritage or listed-building compliance. This premium covers specialist joinery work and materials that match original designs.
If your home is in a conservation area or is a listed building, timber is often the only permitted option. You should check with your local planning authority before ordering any windows.
Annual energy savings from switching to double-glazed timber casement windows
Double-glazed timber casement windows have a U-value of 1.2 to 1.6 W/m²K (Energy Saving Trust, 2026). For a typical three-bed semi-detached house, switching from single to double-glazed timber casement windows saves £150 to £250 per year on heating bills (DESNZ, 2026).
uPVC double-glazed windows have a U-value of 1.4 to 1.8 W/m²K and save £130 to £220 per year. The payback period for timber casement windows is 5 to 8 years. For uPVC, it is 3 to 5 years. Payback period means how long the energy savings take to cover the upfront cost of the windows.
These savings assume you are replacing single-glazed windows with double-glazed ones. If you already have double glazing, upgrading to triple glazing or low-E coated timber windows may save less.
Quick numbers timber casement windows versus uPVC – cost, lifespan, and energy performance
| Factor | Timber casement windows | uPVC casement windows |
|---|---|---|
| Average cost per window (supply and fit) | £800–£1,200 | £400–£700 |
| Annual energy saving (three-bed semi) | £150–£250 | £130–£220 |
| U-value (W/m²K) | 1.2–1.6 | 1.4–1.8 |
| Typical lifespan (years) | 30–50 | 20–25 |
| Maintenance frequency (years) | 4–6 (repaint or stain) | Occasional cleaning only |
Source: Energy Saving Trust, 2026 and DESNZ, 2026.
Timber casement windows have a longer lifespan but require more care
Timber casement windows last 30 to 50 years with proper maintenance (Energy Saving Trust, 2026). uPVC windows last 20 to 25 years. This longer lifespan means timber windows may need replacing less often over the lifetime of your home.
Timber requires repainting or staining every 4 to 6 years (DESNZ, 2026). uPVC needs only occasional cleaning with soap and water. Untreated timber can rot within 5 to 10 years, especially near coastal areas where salt and moisture accelerate decay.
If you live within 5 miles of the coast, you should use a marine-grade paint or stain. Regular checks for cracked paint, swollen joints, or soft wood are essential. Catching problems early avoids costly repairs.
The direct answer timber casement windows cost more upfront but offer lower lifetime carbon impact
Timber casement windows have 30 to 40 percent lower embodied carbon than uPVC over a 60-year lifecycle (DESNZ, 2026). Embodied carbon means the total greenhouse gases released during production, transport, installation, use, and disposal of the product.
The initial cost premium of £300 to £500 per window is offset by a longer lifespan and lower replacement frequency. Timber windows can last twice as long as uPVC, meaning one timber installation may replace two uPVC installations over 50 years.
For listed buildings or conservation areas, timber is often the only permitted option. You cannot install uPVC in these settings without special permission. Timber also offers better sound insulation and a more traditional appearance.
How to verify a timber casement window installer is certified
Before hiring an installer, check three key certifications. First, MCS certification is required for energy performance claims and is needed if you plan to apply for grants like ECO4 (MCS, 2026). Second, TrustMark registration ensures the installer meets government-endorsed standards for quality and customer protection (TrustMark, 2026).
Third, FENSA certification covers building regulations compliance for replacement windows (FENSA, 2026). FENSA-registered installers self-certify that their work meets Part L of the Building Regulations, which covers energy efficiency.
For heritage installations, ask the installer for evidence of Conservation Area or listed building consent. Your local planning authority can confirm whether consent is needed. Installing windows without proper consent can lead to enforcement action and fines.
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Annual maintenance cost for timber casement windows
Annual maintenance for timber casement windows costs £50 to £100 per window (Energy Saving Trust, 2026). This includes repainting or staining every 4 to 6 years, checking seals, and oiling hardware. If you neglect maintenance, rot repair costs £200 to £500 per window (TrustMark, 2026).
uPVC maintenance costs £0 to £20 per year per window, covering only cleaning. Over a 30-year period, timber maintenance adds up to £1,500 to £3,000 per window. uPVC maintenance over the same period is £0 to £600 per window.
However, timber windows may need replacing less often. If you factor in replacement costs, the total lifetime cost of timber and uPVC can be similar. The choice depends on your budget, your home’s style, and whether you value lower carbon impact or lower annual upkeep.
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Frequently Asked Questions
Timber casement windows cost £800 to £1,200 per standard 1.2m x 1.2m window, supplied and fitted (MCS, 2026). uPVC equivalents cost £400 to £700 per window (Energy Saving Trust). Installation labour adds 30-40%.
Yes, double-glazed timber casement windows achieve a U-value of 1.2 to 1.6 W/m²K (Energy Saving Trust, 2026), reducing heat loss by 50-60% compared to single glazing. Single-glazed timber windows lose up to £1,200 annually in heat (Ofgem).
Maintain timber casement windows by repainting or re-varnishing every 3-5 years and checking seals annually. Clean frames with a damp cloth and mild detergent. Use a wood preservative if exposed to damp conditions (Energy Saving Trust).
Timber casement windows offer better aesthetics and are often required for listed buildings or conservation areas, but cost 40-50% more than uPVC. uPVC is cheaper (£400-£700 per window) and requires less maintenance, but timber lasts longer if cared for.
Yes, if your home is in a conservation area or is a listed building, timber casement windows often require planning permission. Check with your local planning authority before ordering. Heritage compliance adds a 10-15% cost premium.
