The Short Answer
uPVC is cheaper upfront and requires less maintenance. Timber looks better, lasts longer, performs better thermally, and adds value to your property. Which matters more depends on your budget, your home, and how long you plan to stay.
Cost
Let's start with the uncomfortable truth: timber sash windows cost 2–3 times more than uPVC. A standard uPVC sash window costs roughly £500–£900 supply and fit. A timber equivalent runs £1,500–£2,500.
That's a significant difference. If you're replacing 10 windows, you're looking at £5,000–£9,000 for uPVC versus £15,000–£25,000 for timber. If budget is your primary constraint, uPVC wins on day one.
But windows are not a one-time purchase. uPVC has a working lifespan of 20–25 years. Timber sash windows, properly maintained, last 60–100+ years. Over a 50-year period, timber costs less per year — and you avoid sending the entire frame to landfill every two decades.
| Factor | Timber Sash | uPVC Sash |
|---|---|---|
| Supply & fit (per window) | £1,500 – £2,500 | £500 – £900 |
| Lifespan | 60–100+ years | 20–25 years |
| Cost per year (over 60 years) | ~£30/yr | ~£60/yr (3 replacements) |
| Maintenance | Repaint every 8–12 years | Clean only (but no repair option) |
| End of life | Biodegradable / repairable | Landfill (300+ years to decompose) |
Thermal Performance
Modern timber and uPVC sash windows both achieve similar U-values with the same glazing unit — typically 1.4 W/m²K with a 4/16/4 double glazed unit. On paper, thermal performance is comparable.
The difference is in the frame material. Timber is a natural insulator — it conducts heat 1,500 times less than aluminium and significantly less than uPVC. Timber frames feel warm to the touch in winter. uPVC frames feel cold. In practice, timber windows reduce cold spots around the frame perimeter, which affects comfort more than U-values suggest.
Appearance
uPVC sash windows have improved dramatically. Modern woodgrain foils and slimmer sightlines make them look closer to timber than ever. From across the street, you might not notice the difference.
Step closer and the illusion breaks. uPVC joints are welded — a shiny ridge at every corner. Glazing bars are flat strips stuck to the glass surface, creating no real shadow lines. The frame is hollow and echoes when you knock on it. The proportions are slightly off — uPVC frames must be thicker to compensate for the material's lower structural strength.
Timber sash windows use mortise-and-tenon joints, invisible and clean. Glazing bars cast real shadow lines. The frame has weight, solidity, and warmth. Conservation officers can spot the difference instantly — which is why uPVC is routinely refused in conservation areas across the UK.
Maintenance
This is uPVC's genuine advantage. Install it, wipe it occasionally, forget about it. No painting, no sanding, no coats of anything. For busy homeowners who never want to think about their windows again, uPVC is the hassle-free option.
Timber needs a repaint every 8–12 years with modern microporous paint systems like Sikkens or Teknos. That's a real commitment. However, "maintenance-free" is marketing — uPVC mechanisms still stiffen, seals still fail, and handles still break. The difference is that uPVC cannot be repaired. When it fails, you replace the entire unit. Timber components can be repaired, sanded, and refinished indefinitely.
Resale Value
In London's conservation areas — which cover vast swathes of the city — timber sash windows add 5–10% to property value. uPVC can actively reduce it. Estate agents consistently report that timber windows are among the first features buyers notice.
Outside conservation areas, the premium is smaller but still present. Timber signals quality, care, and permanence. uPVC signals budget, compromise, and "that'll do."
The Verdict
Choose uPVC if: budget is your primary concern, you want zero maintenance, or you're in a modern property where appearance matters less.
Choose timber if: you value craftsmanship, plan to stay long-term, live in a period property or conservation area, or want windows that add value to your home.
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Open the 3D Configurator Book a SurveyEnvironmental Impact
uPVC production releases dioxins. It takes 300+ years to decompose in landfill and is not meaningfully recyclable in the UK. Aluminium smelting produces roughly 12 tonnes of CO&sub2; per tonne of material.
Timber is the only structural building material that absorbs CO&sub2; rather than producing it. A set of timber sash windows for a typical London terrace locks away the carbon equivalent of driving 2,000 miles. Accoya timber is made from FSC-certified, sustainably grown pine using a non-toxic modification process.
Conservation Areas
If you live in a conservation area — and much of inner London is covered — uPVC applications are routinely refused by planning officers. Timber sash windows that replicate the original design are typically the only acceptable replacement. This isn't a disadvantage of timber; it's a recognition that the material is architecturally correct.
We handle conservation area applications regularly and can advise on what your local council requires. Get in touch or see our sash window specification.