In this article, you’ll discover:
- Real cost comparisons including whole-life value (not just upfront prices)
- How thermal performance differs between materials — with actual U-values
- Honest assessments of maintenance requirements for each option
- Which material suits different property types (period homes, modern builds, conservation areas)
- The sustainability truth that manufacturers don’t always tell you
“What’s the best window material?” It’s probably the question we get asked most often. And the honest answer is: it depends.
We manufacture timber windows, so you might expect us to say timber every time. But we’ve been in this industry long enough to know that the right choice varies by property, budget, and priorities. What we won’t do is pretend uPVC or aluminium don’t have their place.
What we will do is give you the facts — real numbers, honest comparisons, and the information you need to make the right decision for your specific situation. No marketing spin.
The Real Cost Picture: Upfront vs Whole-Life
Let’s start with what everyone wants to know: price. But here’s the thing — upfront cost and whole-life cost are very different numbers.
Typical UK Prices (2026)
Prices for standard casement windows, supply only. Installation adds £100-200 per window.
See that cost-per-year column? That’s the number that actually matters. Yes, timber costs more upfront — typically 80-100% more than uPVC. But when you factor in lifespan, timber often works out cheaper over time. And that’s before considering that uPVC can’t be repaired when it fails — you replace the whole window.
Thermal Performance: The Numbers That Matter
With energy costs where they are, thermal performance has become a major factor. Here’s how the materials compare:
Material Conductivity
Timber is naturally insulating — its cellular structure traps air. The thermal conductivity of softwood is around 0.13 W/mK. Aluminium? 160 W/mK. That’s over 1,000 times more conductive.
This is why aluminium windows need thermal breaks — plastic or polyamide barriers that interrupt the metal and reduce heat transfer. Without them, aluminium frames would be thermal bridges, conducting heat straight out of your home.
uPVC falls somewhere in between — it’s a reasonable insulator but not as good as timber.
Whole Window U-Values
The U-value measures how much heat passes through a window — lower is better. Building Regulations currently require 1.4 W/m²K or better for new windows.
- Timber (double glazed): 1.2-1.4 W/m²K
- Timber (triple glazed): 0.8-1.0 W/m²K
- uPVC (double glazed): 1.2-1.6 W/m²K
- Aluminium (double glazed): 1.4-1.8 W/m²K (with thermal break)
Quality timber windows with low-e glass and argon filling consistently achieve the best thermal performance.
Durability and Maintenance: The Honest Truth
Here’s where we need to address the elephant in the room: timber maintenance.
Timber
Yes, timber windows need maintenance. Modern factory-finished timber with microporous coatings needs repainting every 8-12 years. You’ll also want to do annual checks and keep drainage channels clear.
But here’s what many people don’t realise: that maintenance means timber windows can last 60+ years. When issues occur, you repair — a splice for localised rot, sanding and refinishing for worn paint. The whole window rarely needs replacing.
uPVC
uPVC is marketed as “maintenance-free.” And it’s true you won’t be painting it. But uPVC isn’t problem-free:
- After 15-20 years, discolouration starts (especially on south-facing elevations)
- The material becomes brittle with UV exposure
- Seals fail, gaskets perish
- And when it fails? You can’t repair uPVC — you replace the whole window
Aluminium
Aluminium is genuinely low maintenance — powder-coated finishes last 25-30 years, and the material doesn’t rot, warp, or degrade like uPVC. The main issues are seal failure and thermal break degradation in cheaper products.
Aesthetics: Which Suits Your Property?
This is where the choice often becomes clearer.
Period Properties and Conservation Areas
For Victorian, Edwardian, or Georgian properties — especially in conservation areas — timber is often the only appropriate choice. Planning authorities typically reject uPVC on listed buildings and may refuse it in conservation areas.
Timber sash windows with authentic profiles, slim glazing bars, and period-appropriate detailing maintain the character that makes these properties special.
Modern and Contemporary Buildings
For modern architecture with large glazing areas and minimal frames, aluminium often makes sense. The strength allows for slimmer profiles and larger spans. The clean, industrial aesthetic suits contemporary design.
That said, timber can also work beautifully in modern homes — particularly flush casement windows with their clean lines.
Standard Residential
For typical UK housing stock — 1930s semis, post-war estates, modern developments — any material can work. This is where budget and priorities drive the decision.
Sustainability: The Full Picture
We’ve covered this in detail elsewhere, but here’s the summary:
- Embodied carbon: Timber ~14kg per frame, uPVC ~160kg, aluminium ~200kg
- Carbon storage: Only timber stores carbon throughout its lifespan
- End of life: Timber is biodegradable or recyclable; uPVC degrades with recycling; aluminium is infinitely recyclable but energy-intensive to process
- Longevity: One set of timber windows replaces 2-3 sets of uPVC over the same period
Making Your Decision: A Practical Guide
Choose timber if:
- You own a period property or live in a conservation area
- Long-term value matters more than upfront cost
- Sustainability is a priority
- You want windows that can be repaired, not replaced
- Maximum thermal performance matters
Choose aluminium if:
- You have a contemporary property with large glazing areas
- You want slim frames and maximum glass
- Zero maintenance is essential
Choose uPVC if:
- Budget is the primary constraint
- You’re not in a conservation area
- You plan to move within 15-20 years
Frequently Asked Questions
The Bottom Line
There’s no universally “best” window material — it depends on your property, budget, and priorities. But if you’re looking at the full picture — cost over time, thermal performance, sustainability, repairability, and aesthetics — timber wins in most categories.
At Timber Windows Direct, we manufacture bespoke timber windows in engineered pine, meranti, and oak. We’re happy to discuss whether timber is right for your specific situation — and if it’s not, we’ll tell you. Get in touch for honest advice and a free quote.
