Aluminium, Timber or uPVC: 10 Years of Performance Data from Our Installation Teams
2025 UK data reveals how your frame choice impacts energy bills by £120-£395 annually and property value by 5-10%. 50+ years expertise analysing aluminium vs timber vs uPVC performance.
Quick Answer
Aluminium lasts longest (40-50 years) with minimal maintenance and the slimmest sightlines (35mm). Best for: contemporary designs, coastal locations, large-span glazing.
Timber offers the best thermal performance (U-values 1.2-1.4 W/m²K) and natural beauty. Hardwood lasts 50-60 years. Best for: listed buildings, conservation areas, period properties.
uPVC is most affordable with excellent thermal efficiency (1.2-1.4 W/m²K), lasting 20-35 years. Best for: budget-conscious projects, practical applications. Planning a new glass extension? Explore our bespoke Orangery extensions for more inspiration.
• UK homes lose heat 3x faster than German homes (tado° research)
• 25-30% of your heating escapes through windows and doors
• Average UK energy bill: £1,755/year (Ofgem Q4 2025 price cap)
• A-rated windows can save £120-£395 annually (Energy Saving Trust)
• Quality conservatories add 5-10% to property value (RICS, Savills)
Stand in front of three identical conservatories—aluminium, timber, uPVC—and they might look similar. But over 10, 20, 30 years? The differences become staggering. We’re talking £10,000+ in energy bills, maintenance costs, and property value impact.
Here’s a number that should stop you in your tracks: 55% of UK homes only meet insulation standards set in 1976 or earlier, according to a recent EDF study of 25 million properties. That means if you’re planning a conservatory or glass extension, the frame material you choose today will determine whether you join the majority wasting money on heating, or become one of the smart minority enjoying lower bills and higher property values.
The financial stakes are significant. With the Ofgem price cap currently at £1,755 annually for a typical household (Q4 2025), and energy bills still 45% higher than pre-crisis 2021 levels according to the House of Commons Library, every percentage of heat loss matters. Research from the Glass and Glazing Federation shows that replacing pre-2002 double glazing with current standards could save up to £395 per year.
At Room Outside, we’ve installed thousands of glass extensions across Surrey, Kent, West Sussex, Hampshire, and London over four decades. This guide distils that experience into actionable guidance, backed by current UK market data and Building Regulations requirements.
UK Glazing Market: The Numbers That Matter
| UK Market Data | Figure |
|---|---|
| Annual glazing installations (UK) | 1.9 million |
| Homes with full double glazing | 88% (up from 79% in 2012) |
| uPVC market share | 75% |
| Pre-2002 glazing still installed | 23% of housing stock |
| Heat loss through windows | 18-30% of total |
| Double glazing heat loss reduction | Up to 60% vs single glazing |
| UK homes requiring retrofit by 2035 | 25 million (£12bn opportunity) |
| Property value increase (quality conservatory) | 5-10% |
Sources: English Housing Survey 2022-23, GGF Heat Loss Report 2023, Energy Saving Trust, Ofgem, RICS, Savills
The Retrofit Imperative
With 25 million UK homes requiring retrofit by 2035 to meet net-zero targets, your frame choice isn’t just about today—it’s about future-proofing. Properties with poor thermal performance face declining value as energy efficiency becomes increasingly important to buyers and mortgage lenders.
Building Regulations: What You Must Know
The regulatory landscape is tightening. Part L of the Building Regulations, updated in 2022, already requires replacement windows to achieve U-values of 1.4 W/m²K or better. The Future Homes Standard, taking effect from 2025, will push new-build requirements even further—with U-value targets potentially dropping to 0.8-1.2 W/m²K.
Current Requirements
- Replacement windows: 1.4 W/m²K maximum
- New-build windows: 1.2 W/m²K recommended
- Conservatories: Thermally separated from house
- Glass extensions: Full Building Regs compliance
Future Requirements (2025+)
- Future Homes Standard: 0.8-1.2 W/m²K for new builds
- Rental properties: Minimum EPC Band C from 2026
- Existing homes: Increasing pressure to retrofit
- Potential triple glazing requirement for some areas
For homeowners planning a conservatory, this means your frame choice must support glazing that meets or exceeds these thresholds. According to the GGF, modern windows to current standards perform 50% better than pre-2002 double glazing and 70% better than single glazing.
Critical consideration: While conservatories are often exempt from full Building Regulations when thermally separated from the main house, glass extensions always require full compliance. Many homeowners don’t realise their “conservatory” is actually a glass extension requiring Building Control approval.
Aluminium Frames: The Premium Choice for Longevity
Modern thermally broken aluminium has transformed what was once a material known for cold bridging into a high-performance option. For homeowners prioritising aesthetics and longevity, aluminium delivers.
Lifespan: 40-50+ Years
Aluminium consistently outperforms other frame materials for longevity. The material will not warp, swell, crack, or become brittle regardless of temperature extremes. For coastal properties in Kent or West Sussex, where salt air accelerates degradation of other materials, aluminium’s corrosion resistance proves particularly valuable when specified with marine-grade powder coating.
Thermal Performance: 1.6 W/m²K (Thermally Broken)
Contemporary thermally broken aluminium frames achieve U-values around 1.6 W/m²K, meeting Building Regulations. The thermal break—a polyamide barrier between inner and outer profiles—prevents the cold bridging that plagued earlier aluminium systems. Premium systems approach 1.4 W/m²K.
Sightlines: The Slimmest Available (35mm+)
Aluminium’s strength-to-weight ratio allows for profiles as slim as 35mm, compared to 70mm or more for uPVC. This translates directly into more glass and less frame. For contemporary glass box extensions or large-span glazing, this difference is significant—potentially 20% more visible glass area.
Cost & Value: £17,500-£33,300
Aluminium commands approximately 25% premium over uPVC. However, calculated over a 40-year service life rather than 25 years, the cost-per-year often favours aluminium. A typical aluminium conservatory costs £17,500-£33,300 depending on size and specification.
Sustainability Factor: 95% Recyclable
Recycling aluminium requires only 5% of the energy needed to produce virgin material. Industry estimates suggest up to 75% of all aluminium ever produced remains in use today. For environmentally conscious homeowners in South East England, this represents significant lifecycle advantages.
Timber Frames: Natural Beauty, Natural Insulation
Timber occupies a unique position in the UK market. For period properties, listed buildings, and conservation areas across London and the South East, timber often represents not merely a preference but a planning requirement.
Lifespan: 30-60+ Years (Species Dependent)
Softwood frames without regular treatment may last 25-35 years. Hardwood species (oak, mahogany, teak) can last 50-60 years or more with proper maintenance. Oak-framed windows from the Middle Ages survive in historic buildings across Britain.
Thermal Performance: 1.2-1.4 W/m²K (Best in Class)
Wood is a natural insulator. Softwood timber frames typically achieve U-values between 1.2 and 1.4 W/m²K—the best of any frame material. Timber frames feel warm to the touch even in winter.
Maintenance: High (Repainting Every 4-7 Years)
Timber demands commitment. Repainting every 4-7 years is essential to prevent moisture ingress and UV damage. Over 40 years, this represents 6-10 maintenance cycles—significant time and cost investment.
Cost & Value: £20,925-£39,975
Timber conservatories cost approximately 50% more than uPVC equivalents. However, for period properties in the South East, timber may be the only option that satisfies planning requirements and maintains property character.
Planning reality check: Many conservation areas across Surrey, Kent, and West Sussex explicitly require timber frames for extensions. Attempting to use uPVC or aluminium in these areas often results in planning refusal, regardless of thermal performance.
uPVC Frames: The Value Proposition
Unplasticised polyvinyl chloride dominates the UK market with approximately 75% market share. It offers a compelling balance of performance, cost, and convenience.
Lifespan: 20-35 Years
Quality uPVC frames typically last 20-35 years. Modern formulations resist discolouration and brittleness better than earlier generations. However, uPVC cannot match the multi-decade longevity of aluminium or hardwood timber.
Thermal Performance: 1.2-1.4 W/m²K (Excellent)
Modern multi-chambered uPVC profiles achieve excellent U-values of 1.2-1.4 W/m²K. The multiple internal chambers trap air, creating effective insulation. Contemporary uPVC systems routinely achieve A+ energy ratings.
Maintenance: Minimal
An occasional wipe with soapy water maintains appearance; no painting required. This practical advantage appeals to many homeowners.
Cost & Value: £13,950-£26,650 (Baseline)
uPVC offers the most accessible price point. The bulkier 70mm+ frame profiles and shorter lifespan should be factored into value assessments, but for budget-conscious projects, uPVC remains compelling.
The Recycling Reality
According to BRE, uPVC can be recycled over 10 times without degradation—a potential useful life of 400 years through recycling. Many manufacturers now use 30-60% recycled content in new profiles, significantly reducing environmental impact.
Complete Comparison: All Three Materials at a Glance
| Factor | Aluminium | Timber | uPVC |
|---|---|---|---|
| Typical U-Value | 1.6 W/m²K | 1.2-1.4 W/m²K | 1.2-1.4 W/m²K |
| Expected Lifespan | 40-50+ years | 30-60 years* | 20-35 years |
| Maintenance | Minimal | High (4-7yr cycle) | Minimal |
| Frame Width | 35mm+ (slimmest) | 55mm+ | 70mm+ (widest) |
| Typical Cost Range | £17.5k-£33k | £21k-£40k | £14k-£27k |
| Best For | Contemporary, coastal, large-span | Listed, conservation, period | Budget-conscious, practical |
*Timber lifespan varies by species: softwood 25-35 years, hardwood 50-60+ years
The Hidden Cost Calculation
When comparing costs, consider the total cost of ownership over 30 years:
- Aluminium: Higher initial cost ÷ 40-50 years = lowest annual cost
- Timber: Higher initial cost + maintenance costs ÷ 50-60 years = moderate annual cost
- uPVC: Lower initial cost ÷ 20-35 years + replacement cost = potentially highest annual cost
The “cheapest” option today might be the most expensive over your property’s lifetime.
How Your Frame Choice Impacts Property Value
The data on property values is compelling. According to research from Nationwide, RICS, Savills, and Checkatrade:
The Warning Signal
Poor-quality conservatories with inadequate thermal performance can actually devalue your property. Estate agents report that old polycarbonate-roofed conservatories that are unusable in summer and winter are increasingly seen as a liability rather than an asset. For more on creating a comfortable, year-round space, see expert tips on conservatory interiors.
Value Destroyers
- Seasonal conservatories (too hot/cold for 4-6 months)
- Poor-quality uPVC with discolouration or warping
- Inappropriate materials for property type/area
- Dated designs with polycarbonate roofs
- Non-compliant structures requiring remediation
Value Enhancers
- Year-round usable spaces with advanced glazing
- Material-appropriate for property and location
- Architecturally integrated design
- High EPC performance ratings
- Quality materials with long warranties
In the South East: An A/B EPC rating adds £112,000+ to property value. Moving from EPC D to C can add 3% (£9,000) to property value. Your frame choice directly contributes to these ratings.
How to Choose: A Decision Framework
Choose ALUMINIUM when:
You want minimal frame intrusion and maximum visible glass area, particularly for contemporary glass box extensions or large-span glazing.
You’re in Kent, West Sussex, or other coastal areas where salt air accelerates degradation of other materials.
You value minimal upkeep and want a structure that will last 40-50+ years without significant maintenance.
Your property has modern architecture that suits clean lines and minimal profiles.
Choose TIMBER when:
Planning regulations require traditional materials, particularly in South East conservation areas and listed properties.
You’re extending a Victorian, Edwardian, or Georgian property where timber maintains architectural integrity.
You value the natural beauty of wood and its warm aesthetic qualities.
You understand and accept the 4-7 year repainting cycle required to maintain timber’s longevity and appearance.
Choose uPVC when:
You need the most cost-effective solution that still delivers excellent thermal performance.
You want a “fit and forget” solution with minimal ongoing upkeep requirements.
You value uPVC’s track record of delivering excellent thermal efficiency at accessible price points.
Functionality and value are more important than achieving the absolute finest architectural details.
The 30-Year Financial Analysis: What the Numbers Really Say
Let’s translate these technical specifications into real financial impact over a 30-year period—the typical timeframe homeowners consider when investing in their property.
| Cost Category | Aluminium | Timber (Hardwood) | uPVC |
|---|---|---|---|
| Initial Cost (15m²) | £25,500 | £30,450 | £20,300 |
| Maintenance (30 years) | £1,500 | £12,000 (5 cycles) | £500 |
| Energy Savings (vs single glazing) | £11,850 | £12,825 | £12,825 |
| Replacement Cost (if needed) | £0 | £0 | £30,450 (year 25) |
| Property Value Increase | £25,000 | £30,000 | £20,000 |
| NET 30-YEAR POSITION | +£60,850 | +£60,375 | +£22,575 |
The Surprising Reality
While uPVC appears cheapest initially, the requirement for complete replacement around year 25 transforms the financial picture. Over 30 years, aluminium and timber deliver 2-3x better net financial position despite higher initial costs.
Key assumption: 5% property value uplift for quality conservatory, £395 annual energy savings (Energy Saving Trust maximum), maintenance costs based on Room Outside installation data across Surrey, Kent, and West Sussex.
Regional variation: In South East England, where property values are higher and planning restrictions stricter, timber and aluminium often deliver even greater value uplift compared to national averages.
Begin Your Frame Selection Journey
Your conservatory frame choice isn’t just about aesthetics or initial cost. It’s a 30-year commitment that impacts your energy bills, maintenance schedule, property value, and daily living experience.
Your Next Steps
Step 1: Assess Your Context
- Check planning restrictions (conservation area?)
- Evaluate property style and architectural character
- Consider location (coastal, rural, urban?)
- Review budget for total 30-year ownership
Step 2: Consult Experts
- Discuss with Room Outside’s installation teams
- Review case studies from similar properties
- Get site-specific technical advice
- Understand planning implications for your area
The Room Outside Advantage
With 50+ years installing across South East England, we understand not just the technical specifications but the practical realities of each material in different contexts. We’ve seen aluminium frames weathering coastal storms in Kent, timber aging gracefully in Surrey conservation areas, and uPVC delivering value in practical applications across London. Looking for inspiration? View our project gallery to see completed projects.
Our advice always begins with understanding your property, your lifestyle, and your long-term objectives—not with product recommendations.
Frame material selection rarely has a single correct answer. The optimal choice emerges from your property’s character, your lifestyle, your budget, and your priorities for the decades ahead.
At Room Outside, we work with all three frame materials because each serves different requirements. Whether you’re considering an orangery in Kent, a contemporary glass extension in Surrey, or a refurbishment anywhere across the South East, our teams have decades of combined experience to guide your decision.
FAQ: Frame Materials for Conservatories and Glass Extensions
Which conservatory frame material lasts the longest?
Aluminium offers the longest expected lifespan at 40-50+ years with minimal maintenance. Hardwood timber can match this (50-60 years) but requires repainting every 4-7 years. uPVC typically lasts 20-35 years before requiring replacement.
How much can new windows save on energy bills?
A-rated windows can save £120-£395 annually depending on property type and existing glazing. The Energy Saving Trust estimates £195/year for a semi-detached home. Over 25 years, total savings can exceed £4,875 against pre-2002 double glazing.
Is aluminium or uPVC better for thermal efficiency?
uPVC marginally outperforms standard aluminium, achieving U-values of 1.2-1.4 W/m²K versus 1.6 W/m²K for thermally broken aluminium. Both meet current Building Regulations. Timber achieves the best thermal performance at 1.2-1.4 W/m²K.
Do conservatories add value to UK properties?
A well-built conservatory can add 5-10% to property value according to RICS, Savills, and Checkatrade. However, poor-quality builds with inadequate thermal performance can actually devalue properties, particularly old polycarbonate-roofed structures unusable for 4-6 months yearly.
What U-value do windows need for Building Regulations 2025?
Replacement windows require 1.4 W/m²K or better under Part L Building Regulations. New-build targets are 1.2 W/m²K. Future Homes Standard 2025 may require 0.8-1.2 W/m²K for new builds, potentially requiring triple glazing in some applications.
Which frame material has the slimmest sightlines?
Aluminium provides the slimmest profiles at 35mm or less, compared to 55mm+ for timber and 70mm+ for uPVC. This means up to 20% more visible glass area, particularly important for contemporary glass box extensions and large-span glazing.
Ready to Discuss Your Frame Options?
Work with conservatory specialists who understand not just materials specifications, but how they perform across different South East locations—from coastal Kent to conservation areas in Surrey and contemporary London extensions.
