Secondary Glazing for Crittall Windows
Perfect for preserving original Crittall windows completely while achieving 50-65% energy reduction and avoiding £12,000-£18,000 replacement costs. Our secondary glazing stops metal frame heat conduction, eliminates condensation on Crittall frames, and reduces noise by 70-80%, all while maintaining your property's authentic 1920s-1950s architectural heritage. Ideal for listed buildings and conservation areas. Reversible solution protects heritage value.
Crittall heritage specialists • Grid aesthetic preservation experts • Listed Art Deco building approved • W20/W40 experience
Perfect for Art Deco buildings, 1930s homes, factory conversions, modernist villas, and any property with original W20/W40 Crittall windows throughout London.
Get Your Free Crittall AssessmentWhat Are Crittall Windows?
Iconic British design heritage from the 1920s-1950s
Crittall windows are iconic metal-framed windows from the 1920s-1950s that represent British design heritage at its finest. Created by Francis Crittall & Company, these distinctive windows epitomize modernist architecture, embodying the Art Deco period's Bauhaus influence and industrial aesthetic. Their geometric grid patterns and slim steel frames are instantly recognizable design icons that continue to define property character nearly a century later.
The classic W20 and W40 ranges showcase various grid configurations, from 6-pane domestic windows to expansive 12-pane industrial installations. These windows emerged during the modernist architectural revolution, representing modernity, progress, and industrial sophistication. Today, they maintain design icon status, featured in architecture publications and sought after by design-conscious buyers who appreciate authentic heritage.
Where You'll Find Crittall Windows
- 1930s suburban homes: Middle-class modernity with original period features
- Art Deco buildings (1920s-1930s): Geometric elegance in listed buildings
- Factory/warehouse conversions: Authentic industrial heritage in urban lofts
- Modernist villas: Clean lines with glass-focused design
- Schools and public buildings: Often listed institutional architecture
- Commercial buildings: Offices and retail from early-mid 20th century
Why Owners Love Their Crittall Windows
The iconic grid pattern literally defines property character, creating an irreplaceable connection to the modernist movement. Authentic Crittall adds significant property desirability and value—they're currently trendy in industrial chic and contemporary design.
The slim steel profiles and large glass areas represent architectural heritage that simply cannot be replicated with modern alternatives. Typical Crittall features black or dark green metal frames with geometric patterns visible from the street that define the entire property's exterior character.
The Crittall Dilemma: Heritage vs Performance
Understanding the challenges faced by Crittall window owners
Metal Frame Heat Conduction Crisis
Steel frames conduct heat rapidly, creating massive thermal bridges that make Crittall windows extremely energy-inefficient. The metal becomes cold to touch in winter, causing heavy condensation, while heating up dramatically in summer. Combined with single-glazed glass, this creates extreme energy loss—modern homes are typically 50-70% more efficient than properties with original Crittall windows.
Thin Single Glazing Problems
Original Crittall features 3-4mm single-pane glass with zero thermal performance—heat passes straight through with minimal resistance. This creates cold zones near windows, making rooms uncomfortable and energy costs astronomical.
Draught and Air Leakage Issues
After 80-100 years, Crittall window seals have typically failed, creating multiple draught points where wind literally whistles through. The geometric grid design, while beautiful, creates numerous joints that can develop air leaks.
Noise Amplification Through Thin Glass
The thin single glazing provides zero sound insulation, while metal frames can actually transmit vibration and sound. This is particularly problematic in urban and industrial locations where Crittall windows are common.
Condensation Crisis on Metal Frames
Cold metal frames combined with indoor moisture create heavy condensation that literally runs down frames daily during winter months. Grid bars are particularly affected, leading to mold around frame surrounds, rust on steel frames, and paint blistering.
Prohibitively Expensive Replacement Costs
New Crittall windows cost £800-£1,500 per window as a heritage product requiring specialized manufacturing. A typical property needs £10,000-£18,000 including installation for complete replacement.
Planning and Listed Building Restrictions
Many Crittall properties are protected—Art Deco buildings are often listed, and conservation areas commonly restrict alterations. Planning authorities typically refuse replacement because original Crittall windows are considered heritage features.
The Aesthetic Preservation Dilemma
The Crittall grid pattern represents THE defining property feature that owners are terrified of losing. Any replacement destroys the authentic 1920s-1950s heritage fabric that design-conscious buyers specifically seek.
Your Impossible Choice:
You love your iconic Crittall grids for their property character, architectural heritage, and design cachet, BUT they're freezing, draughty, noisy, condensation-plagued, and expensive to heat. Replacement would cost £10,000-£18,000, might be refused by planning authorities, and would destroy your property's authentic heritage value forever.
The Solution:
Secondary glazing preserves your Crittall grids completely while solving every performance problem for 50-70% less cost than replacement.
How Secondary Glazing Preserves Your Crittall Aesthetic 100%
Complete grid pattern preservation with zero external alteration
From Exterior (Street View)
Your property's appearance remains absolutely unchanged. The original Crittall grid stays fully visible from the street because secondary glazing is installed internally with zero external alteration.
Your property character, street scene, and iconic Crittall look remain completely intact. This invisible-from-outside approach ensures planning-friendly approval since there's no external appearance change whatsoever.
From Interior
A slim secondary glazing frame (20-30mm aluminum) installs unobtrusively in the window reveal. You see through the transparent secondary glass to the original Crittall grid behind, creating a layered aesthetic.
Both the secondary frame and original Crittall grid remain visible in an attractive depth effect. The Crittall grid pattern stays the dominant visual feature—it's never hidden or obscured.
Color-Matching Options
Secondary frames can be powder-coated black or grey to blend seamlessly with your Crittall, or white for modern contrast that suits contemporary interiors. Many owners discover they actually prefer the layered industrial look of both metal frames working together.
Why the Grid Is Never Lost
- Secondary glazing uses completely transparent glass—you see straight through to the Crittall grid behind
- The Crittall remains the primary visual element with its grid pattern and metal frames staying prominent
- Installation in the window reveal doesn't obstruct the Crittall face view
- Reveals simply gain 50-100mm depth with secondary glazing sitting inside while Crittall remains at the exterior edge
Art Deco Building
Black Crittall 9-pane grids with black aluminum secondary frames create a cohesive industrial aesthetic—from street zero change, from inside both black frames look intentional with grid perfectly preserved.
Factory Conversion
W40 warehouse Crittall with large grids plus grey secondary frames maintains industrial loft character while enhancing the layered metal aesthetic.
1930s Suburban Home
Cream Crittall 6-pane grids with white secondary frames preserves authentic 1930s character—street view unchanged, interior maintains period feel.
Complete Reversibility
Secondary glazing removes completely, allowing return to original single-glazed Crittall if ever desired. There's zero permanent alteration—your Crittall windows remain completely intact beneath, protecting heritage value for future generations.
"I was terrified secondary glazing would hide my beautiful Crittall grids. I can't believe how well it works—the grids are still the main feature, just with a modern performance boost. From the street, you'd never know there's secondary glazing. It's absolutely perfect."
Comprehensive Benefits: Why Secondary Glazing Transforms Crittall Performance
Complete solutions for every Crittall challenge
Transform Thermal Efficiency
The 50-100mm air gap between your Crittall and secondary glazing breaks the thermal bridge completely. While your metal Crittall frames still conduct heat, the insulating air gap prevents that cold from transferring into your room.
50-65% reduction in heat loss • £500-£900 annual savings typical
Learn about thermal insulation →Prevent Condensation on Crittall Frames
The interior surface becomes the warm secondary glazing rather than cold Crittall metal. Condensation moves to the cold side between Crittall and secondary glazing, away from your living space.
Your visible interior surface stays completely dry—no more daily wipe-down
Dramatically Improve Acoustic Performance
Achieves 70-80% noise reduction through a dual barrier effect: your Crittall single glazing plus secondary glazing plus the large air gap. Laminated acoustic glass options handle extreme noise situations.
70-80% noise reduction • Transforms urban Crittall properties
Explore acoustic solutions →Complete Draught Elimination
Secondary glazing seals the entire opening with high-quality brush seals, creating zero air leakage. Aged Crittall draught points get sealed behind the secondary glazing—failures in original sealing no longer matter.
Wind no longer penetrates • Comfortable rooms year-round
Preserves Authentic Crittall Heritage Value
Your original Crittall remains completely intact with zero alteration to heritage fabric. Authentic 1920s-1950s windows stay preserved, maintaining property value and architectural heritage.
Grid aesthetic unchanged • Property desirability actually increases
Avoids Catastrophic Replacement Costs
Secondary glazing costs £3,500-£7,000 for typical properties versus £10,000-£18,000 for new Crittall replacement. This saves £5,000-£11,000 (50-70% cheaper) while achieving equivalent performance.
Save £5,000-£11,000 • Faster 4-7 year payback
Read our cost guide →Listed Building & Planning Advantages
The reversible solution gains approval for listed buildings because there's no permanent alteration. With no external appearance change and internal-only addition, it's usually permitted development.
Conservation officers support it • Crittall replacement often refused
Planning guide →Add Modern Security to Heritage Crittall
Secondary glazing creates an additional barrier that intruders must breach before reaching Crittall windows. Laminated glass options hold when broken, delaying intrusion.
Ground floor Art Deco properties get meaningful security enhancement
Security benefits →Maintains Full Crittall Window Operation
Your Crittall windows can still open completely—secondary glazing opens independently through hinged, lift-out, or sliding options. Both window systems function independently.
Full access for ventilation and cleaning • Year-round flexibility
Secondary Glazing Options for Your Crittall Windows
Choose the right system for your specific Crittall type
Hinged Secondary Glazing
£400-£700 per window
Best for:
W20 casement Crittall with opening panels requiring regular access
Operation:
Hinged frame swings open like a door, providing full access to Crittall windows behind
Configuration:
Typically side-hung to match Crittall casement direction, with top-hung available for specific installations
Lift-Out Secondary Glazing
£300-£500 per window
Best for:
Budget-conscious projects, seasonal use, or W40 fixed Crittall installations
Operation:
Panel lifts out completely for occasional cleaning access
Configuration:
Lightweight panels with magnetic catches or clips for easy removal
Fixed Secondary Glazing
£350-£600 per window
Best for:
W40 fixed Crittall that never opens, prioritizing maximum performance
Operation:
Permanently fixed with occasional screw removal for access
Configuration:
Sealed completely around perimeter for optimal thermal and acoustic results
Choosing Your System
Every configuration maintains Crittall grid visibility perfectly—your iconic aesthetic is preserved regardless of chosen system.
Glass Specifications for Crittall Secondary Glazing
Tailored recommendations for Crittall window challenges
Standard Options with Crittall-Specific Guidance
Since your Crittall already has thin single glazing, even 4mm standard secondary glass adds significant performance through the dual-layer effect. Understanding air gap requirements for metal-framed windows is critical - for thermal improvement, the air gap size matters more than glass thickness. Focus on maximizing cavity depth. Learn how to prevent condensation on Crittall frames through proper air gap sizing.
Noise Reduction
For urban Crittall properties, recommend minimum 6.8mm acoustic glass since Art Deco buildings often face busy streets.
Extreme traffic: 8.8-10.8mm laminated options for London properties with heavy traffic exposure.
Security Enhancement
For ground floor Crittall, minimum 6.4mm laminated glass provides protection since original windows are often vulnerable.
Original Crittall often has old locks and thin glass requiring additional security.
Condensation Elimination
Works with any glass configuration—the air gap eliminates interior surface condensation regardless of specific glass choice.
Focus on maximizing air gap depth for best condensation control.
| Glass Type | Best For | Crittall Application |
|---|---|---|
| 4mm Float Glass | Basic thermal improvement | Quiet residential areas, mainly thermal benefits needed |
| 6.4mm Laminated | Enhanced security + moderate acoustic | Ground floor wide windows in accessible locations |
| 6.8mm Acoustic Laminated | Significant noise reduction | Street-facing Crittall, busy residential streets |
| 8.8mm High-Performance | Superior noise reduction | Art Deco buildings facing busy roads |
| 10.8mm Specialist | Exceptional performance | Main roads, railways, flight paths |
| 12.8mm Maximum | Ultimate noise reduction | Most challenging noise situations |
Professional Installation Process for Crittall Properties
7-step Crittall-specific approach
Initial Consultation
Free home visit to identify Crittall type (W20/W40, grid patterns, opening styles), discuss grid preservation concerns, and assess listed building or conservation area status
Detailed Survey
Precise Crittall measurement with grid pattern recording, reveal depth assessment, frame condition evaluation, and grid photography for reference
Specification & Quotation
System recommendation (hinged/lift-out/fixed per window), glass specification, frame color matching or contrast options, complete cost breakdown with grid preservation assurance
Custom Manufacturing
Secondary frames manufactured to exact Crittall dimensions with specified color-matching (4-6 weeks typical)
Professional Installation
Installation in Crittall reveals with zero alteration to original windows, grid visibility confirmation, sealing verification (2-4 hours per window)
Quality Assurance
Grid aesthetic verification from interior and exterior views, operation testing, condensation explanation, owner concern resolution
Aftercare Support
Comprehensive warranty, maintenance guidance for simple cleaning, ongoing support with grid preservation guarantee
Installation Considerations
- Zero alteration to Crittall heritage fabric
- Interior-only work requiring no scaffolding or external access
- Minimal disruption allowing continued residence occupancy
- Grid pattern remains 100% intact throughout entire process
Investment: Secondary Glazing vs Crittall Replacement Costs
Understanding the significant cost savings
Secondary Glazing Investment
- Per window: £300-£700
- Typical Art Deco property: £3,500-£7,000 (10-15 windows)
- Large factory conversion: £7,000-£12,000
New Crittall Replacement
- Per window: £800-£1,500
- Typical property: £10,000-£15,000
- Professional installation: £2,000-£3,000
- Total project: £12,000-£18,000
Modern Crittall-Style Imitation
- Per window: £600-£1,000
- Typical property: £6,000-£12,000
- Major drawback: Loses authentic heritage value and property character
Secondary Glazing Value Proposition
- Save £5,000-£11,000 versus authentic Crittall replacement
- 50-70% cheaper than any replacement option
- Preserves original Crittall maintaining heritage value and property premium
- Equivalent performance achieving similar thermal and acoustic results
- Reversible solution keeps original Crittall intact for future generations
- Planning-friendly while replacement often gets refused
Return on Investment
- Annual energy savings: £500-£900 (Crittall properties have significant glass areas)
- Payback period: 4-7 years typical
- System lifespan: 20-25 years with quality installation
- Total lifetime savings: £10,000-£18,000 over 20 years
Finance options available to spread investment costs over manageable periods.
Real Crittall Success Stories
Actual results from London Crittall property owners
Grade II Art Deco Building, Maida Vale
Original 1932 Crittall Throughout
The Challenge:
Listed Art Deco building with 12 original black W20 Crittall windows featuring 6-pane grids. Single-glazed windows created a freezing flat with condensation running down frames daily. Annual heating bills reached £3,200. Applied for Crittall replacement (£14,000 quote) but listed building consent was REFUSED.
The Solution:
Hinged secondary glazing installed on all 12 windows with 6.8mm acoustic glass and black powder-coated frames matching existing Crittall. Total investment: £5,200.
Outstanding Results:
- 61% heating bill reduction saving £7,808 over 4 years
- Condensation eliminated completely—frames now stay dry
- 76% traffic noise reduction makes A5 barely audible
- Crittall grids preserved 100%—conservation officer approved
- Investment £5,200 vs £14,000 refused replacement = 0.7-year payback
I was heartbroken when they refused my Crittall replacement. I love my 1932 grids but the flat was unbearable—freezing, condensation everywhere, deafening traffic. Secondary glazing has been miraculous. The grids look exactly the same from the street, my heating bills are reasonable for the first time ever, and the flat is finally quiet.
Factory Conversion Loft, Hoxton
Warehouse W40 Crittall, 3m x 2m Windows
The Challenge:
Converted textile factory with huge W40 warehouse Crittall featuring 12-pane industrial grids (3m x 2m each, 8 windows total). Single-glazed installation created massive heat loss with £4,800 annual energy bills. Extreme noise from Shoreditch nightlife made sleep impossible.
The Solution:
Fixed secondary glazing on all 8 windows (never opened anyway) with 10.8mm high-performance acoustic glass and grey powder-coated frames. Total investment: £8,400.
Outstanding Results:
- 68% heating cost reduction providing £13,056 savings over 4 years
- 84% noise reduction—Shoreditch nightlife barely audible
- Industrial aesthetic enhanced—layered metal frames look intentional
- Crittall grids remain fully visible maintaining warehouse character
- Investment £8,400 vs £18,000 replacement = 0.6-year payback
Our 3m warehouse Crittall windows are stunning—the grids are the entire loft's character. But they were completely impractical: freezing, deafeningly noisy, £400/month heating bills. Secondary glazing has been perfect. The grids still dominate, the grey frames suit the industrial vibe, and the loft is finally comfortable.
Secondary Glazing vs Crittall Replacement Comparison
Side-by-side analysis of your options
| Factor | Secondary Glazing | New Crittall Replacement |
|---|---|---|
| Cost (typical property) | £3,500-£7,000 | £12,000-£18,000 |
| Grid preservation | 100% original Crittall retained | New Crittall (not original heritage) |
| Heritage value | Authentic Crittall preserved | Lose original 1920s-1950s fabric |
| Planning approval | Easy (reversible, internal only) | Often refused (loss of original) |
| Installation time | 2-4 hours per window | Weeks of major replacement work |
| Reversible | Yes (Crittall intact beneath) | No (original Crittall destroyed) |
| Disruption | Minimal (interior only) | Major (removal, disposal, installation) |
| Performance | 50-65% energy, 70-80% noise | Similar performance to new DGU |
| Listed building | Approved (reversible solution) | Usually refused by conservation |
| Property value | Enhanced (authentic + performance) | Risk diminished (lose originality) |
Winner for cost, heritage preservation, and planning approval: Secondary Glazing
Frequently Asked Questions About Crittall Secondary Glazing
Expert answers to common Crittall owner concerns
Transform Your Crittall Windows
Transform your beloved Crittall windows into comfortable, efficient features while preserving their iconic heritage character completely. Contact Secondary Glazing Specialist today for your free Crittall assessment and discover how to save thousands while protecting your property's authentic architectural treasure.