Window Replacement – What You Need to Know Before You Start

Replacing windows is a significant home improvement project that can transform both the appearance and performance of your property. Modern windows offer superior energy efficiency, enhanced security, and improved comfort compared to older installations. With rising energy costs making home efficiency more important than ever, window replacement has become essential for many homeowners looking to reduce bills and increase property value.

If your windows are more than 15 years old, advances in technology mean new installations could make a substantial difference to your home’s energy performance and comfort levels. Today’s windows come in various styles, materials, and performance ratings, giving you options to suit both your budget and aesthetic preferences.

How Much Does Window Replacement Cost?

Cost is typically the primary concern when considering window replacement, as the investment can be substantial. Understanding the various factors that influence pricing helps you budget effectively and make informed decisions.

The average cost for window replacement ranges from £400 to £2,800 per window, depending on several key factors:

Factors affecting window replacement costs:

Window size and style
Frame material choice
Glass specification and energy rating
Installation complexity
Number of windows being replaced
Location and access requirements

Average Window Replacement Costs by Type

Here’s a breakdown of typical costs for different window types:

Window Type	Average Cost Range
Standard uPVC casement	£400 – £800
uPVC sash window	£600 – £1,200
Timber casement	£800 – £1,500
Timber sash window	£1,200 – £2,200
Aluminium window	£500 – £1,100
Bay window	£1,800 – £3,500

Costs include supply and standard installation

You don’t need to replace all windows simultaneously. Many homeowners spread the cost by replacing windows in phases – perhaps focusing on the most problematic areas first or tackling one floor at a time.

When comparing quotes, ensure you’re getting like-for-like comparisons and that all quotes include removal of old windows, proper disposal, and any necessary finishing work.

Choosing Your Window Material

One of the most important decisions in window replacement is selecting the right frame material. Your choice will depend on your property’s style, your budget, and your maintenance preferences.

uPVC Windows

uPVC remains the most popular choice for UK homes, offering excellent value and performance.

Advantages:

Low maintenance requirements
Excellent thermal efficiency
Wide range of colours and finishes
Cost-effective option
Good security features

Considerations:

May not suit period properties
Limited repair options if damaged
Some environmental concerns

Timber Windows

Timber windows offer traditional appeal and environmental benefits.

Advantages:

Authentic appearance for period homes
Environmentally sustainable
Can be repaired and maintained
Excellent insulation properties
Often required in conservation areas

Considerations:

Higher initial cost
Regular maintenance needed
Professional installation essential

Aluminium Windows

Aluminium frames work well for modern properties and larger glazed areas.

Advantages:

Slim profiles maximize glass area
Very strong and durable
Low maintenance
Modern aesthetic appeal
Fully recyclable

Considerations:

Higher cost than uPVC
Can conduct heat if not thermally broken
May not suit traditional properties

Finding a Window Installer

Choosing the right installer is crucial for a successful window replacement project. Look for companies that are members of recognized schemes and have strong local reputations.

What is FENSA and Why Does it Matter?

FENSA is the leading competent person scheme for window and door installation in the UK. FENSA-approved installers can self-certify their work complies with building regulations, which means:

Work meets required standards
You receive proper certification
No need for separate building control approval
Insurance-backed guarantees available

How to Find Experienced Window Installers

Research online: Look for local installers with strong reviews and professional websites.

Check credentials: Ensure installers are FENSA registered or members of similar schemes like CERTASS.

Get multiple quotes: Obtain at least three detailed quotes to compare pricing and approaches.

Ask for references: Request contact details for recent customers to verify quality of work.

Verify insurance: Confirm installers have appropriate public liability and employer’s liability coverage.

The Window Replacement Process

Understanding what to expect during window replacement helps you prepare properly and ensures the project runs smoothly.

Initial Survey and Quotation

A reputable installer will conduct a thorough survey of your existing windows, taking precise measurements and assessing any special requirements. They should provide a detailed written quote covering:

Complete removal and disposal of old windows
Supply and installation of new windows
All necessary hardware and accessories
Building regulation compliance
Cleanup and waste removal
Warranty terms

Preparation for Installation

Timeline: Standard window replacement typically takes 1-3 days depending on the number of windows and complexity.

Access: Installers may work from inside or outside your property depending on the situation. Ground floor windows are usually accessible from outside, while upper floors may require internal access or scaffolding.

Disruption: Window replacement can be messy work. Professional installers should use dust sheets and take measures to minimize disruption, but expect some dust and debris during the process.

What to Expect During Installation

Day 1 – Removal and Preparation: Existing windows are carefully removed, with installers taking care to protect surrounding walls and furnishings. Any necessary structural work or repairs are completed.

Day 2 – Installation: New windows are fitted, ensuring proper alignment, weatherproofing, and security. Each window installation typically takes 2-3 hours for straightforward replacements.

Day 3 – Finishing: Final adjustments, internal and external finishing work, and thorough cleanup complete the installation process.

Installation Methods

From Inside or Outside? Most installers prefer to work from outside where possible to minimize internal disruption. However, they’ll need internal access to ensure proper fitting and compliance with building regulations.

A typical window installation involves:

Removing the old frame completely
Checking and preparing the opening
Installing the new frame with proper insulation
Fitting the glazed units
Adding internal and external finishing
Testing operation and adjusting hardware

Do I Need Building Regulation Approval?

Yes, replacement windows must comply with current building regulations, which cover thermal performance, safety, and ventilation requirements.

FENSA Certification

When you use a FENSA-approved installer, they handle building regulation compliance automatically. You’ll receive a FENSA certificate confirming:

Windows meet thermal performance standards
Installation complies with building regulations
Work has been properly inspected
Appropriate ventilation has been provided

What if I Don’t Have Certificates?

If you’re missing certificates for previous window installations, you can:

Check online databases for FENSA or CERTASS records
Request duplicate certificates (usually £25-£50)
Arrange for local authority inspection
Consider indemnity insurance for property sales

Having proper certification is important for property transactions, as solicitors will request evidence of building regulation compliance.

How Long Does Window Replacement Take?

The duration of window replacement depends on several factors:

Project size: Individual windows can be replaced in a few hours, while whole-house projects may take several days.

Window type: Standard casement windows install faster than complex sash or bay windows.

Access requirements: Ground floor windows are quicker than upper floors requiring scaffolding.

Weather conditions: Installation may be delayed by extreme weather for safety and quality reasons.

Typical timeframes:

Single window replacement: Half day
3-4 windows: 1-2 days
Whole house (8-12 windows): 3-5 days

Professional installers should provide realistic timeframes and keep you informed of progress throughout the project.

What About Mess and Disruption?

Window replacement inevitably creates some mess and disruption, but professional installers take steps to minimize both.

Protective measures typically include:

Dust sheets to protect floors and furniture
Plastic sheeting over doorways
Careful handling to minimize debris
Daily cleanup of work areas
Proper disposal of old windows and materials

You can help by:

Clearing access routes and window areas
Removing or covering nearby furniture
Making arrangements for pets during installation
Being available for any questions or decisions

Most disruption is temporary, and you’ll be able to use your home normally once installation is complete each day.

Energy Efficiency and Performance

Modern windows offer significant improvements in energy efficiency compared to older installations.

Window Energy Ratings

Look for windows with A-rating or better for optimal energy performance. The Window Energy Rating (WER) system considers:

Thermal transmittance (U-value)
Solar heat gain
Air leakage rates

Glass Options

Consider upgrading glass specifications for enhanced performance:

Double glazing: Standard for most applications
Triple glazing: Superior insulation for exposed locations
Low-E coatings: Reduce heat loss while maintaining light transmission
Argon gas fills: Improve thermal performance between panes

Long-term Savings

While energy-efficient windows cost more initially, they typically pay for themselves through reduced heating bills over their 20-25 year lifespan.

Maintenance and Aftercare

Modern windows require minimal maintenance, but some care helps preserve their appearance and performance.

uPVC Window Care

Clean frames with mild detergent solution
Lubricate hinges and locks annually
Clear drainage holes of debris
Check and renew sealants as needed

Timber Window Maintenance

Inspect and touch up paintwork every 2-3 years
Check for any signs of moisture ingress
Maintain regular decoration schedule
Address any minor repairs promptly

Warranty Coverage

Quality installers typically provide:

10-year guarantee on window units
2-year guarantee on installation work
Insurance-backed guarantees for additional security

Is DIY Window Replacement Worth Considering?

While simple glass replacement might be suitable for experienced DIYers, full window replacement is generally best left to professionals.

Challenges of DIY installation include:

Achieving proper weatherproofing
Ensuring building regulation compliance
Having appropriate tools and equipment
Managing potential structural issues
Obtaining proper certification

Professional installation ensures optimal performance, regulatory compliance, and warranty protection.

Getting Started with Your Window Replacement

Ready to proceed with window replacement? Follow these steps:

Assess your needs: Identify which windows need replacement and your priorities
Set your budget: Determine how much you can invest and whether to phase the work
Research installers: Find FENSA-registered companies with good local reputations
Get quotes: Obtain detailed quotations from at least three installers
Check planning requirements: Verify if planning permission or special approvals are needed
Schedule installation: Choose timing that minimizes disruption to your household

Window replacement is a significant investment that can dramatically improve your home’s comfort, efficiency, and value. By choosing quality products and professional installation, you’ll enjoy the benefits for many years to come.