Retrofitting Rooflights: Improving Energy Efficiency in Older Homes

Older homes often exude charm and character, but they frequently fall short when it comes to modern energy efficiency standards. One area that can significantly impact a home's thermal performance is the roof, particularly the rooflights, commonly referred to as skylights. By retrofitting rooflights, homeowners can enhance comfort, reduce energy costs, and even improve the property’s overall Energy Performance Certificate (EPC) rating with solutions from Skylights & Roof Lanterns.

In this article, we explore the benefits of retrofitting rooflights, delve into practical methods to improve their energy performance, and provide guidance on selecting the most suitable options for older homes.

The Importance of Skylights in Older Homes

Skylights have long been celebrated for their ability to bring natural light into interiors, creating a sense of openness and reducing reliance on artificial lighting. However, many skylights installed decades ago were designed without energy efficiency in mind. Older units often feature single glazing or polycarbonate domes that provide minimal insulation.

This inefficiency can lead to:

Heat loss during winter months, increasing heating bills

Solar heat gain during summer, making interiors uncomfortably warm

Drafts and condensation, which may affect the longevity of the roof structure

Modern skylights, however, are engineered with energy performance as a core consideration. By retrofitting older units, homeowners can enjoy the aesthetic and functional benefits of skylights while dramatically reducing energy consumption.

Understanding Skylights Energy Efficiency

Energy-efficient skylights are designed to minimise heat loss while maximising natural daylight. The primary measure of a skylight’s thermal performance is its U-value, which indicates the rate of heat transfer through the unit. The lower the U-value, the better the insulation.

For older homes, retrofitting rooflights to improve skylights energy efficiency involves assessing the current U-value and upgrading to units with improved thermal performance.

Learn how to make your home greener with eco-friendly skylights.

Key Factors Affecting Energy Efficiency

Glazing Type: Double or triple-glazed units significantly outperform single-glazed skylights. Some high-performance units include low-emissivity (low-E) coatings that reflect heat back into the room.

Frame Material: Frames can be made from PVC, timber, or aluminium with thermal breaks. Timber often provides superior insulation, while aluminium frames require thermal breaks to reduce heat transfer.

Installation Quality: Proper installation ensures airtightness, reducing drafts and preventing condensation. Even the most advanced unit will underperform if installed incorrectly.

Retrofitting Rooflights: Techniques and Benefits

Retrofitting rooflights can involve several approaches, depending on the existing structure and desired outcomes. Common strategies include:

Replacing Polycarbonate Domes
Many older skylights use polycarbonate domes, which are prone to yellowing, cracking, and heat loss over time. Replacing these with modern double-glass units or insulated acrylic options can significantly improve thermal performance.

Upgrading Glazing Units
For skylights that allow it, replacing a single-glass unit with double or triple glazing is a straightforward way to improve insulation. Advanced units may also incorporate argon gas fills or low-E coatings to further enhance energy efficiency.

Improving Frame Insulation
Older rooflights often have poorly insulated frames. Retrofitting with frames that include thermal breaks or additional insulation can reduce U-values, making a noticeable difference in heat retention.

Adding Secondary Glazing
In some cases, secondary glazing can be installed inside the existing rooflight, providing additional insulation without replacing the original unit. While this may not provide the same performance as a full replacement, it is a cost-effective option for homes with heritage restrictions.

Sealing and Weatherproofing
Gaps around skylights are a common source of heat loss and draughts. Retrofitting should include proper sealing, flashing upgrades, and ensuring the rooflight integrates seamlessly with the surrounding roof membrane.

How Retrofitting Improves EPC Ratings

An EPC (Energy Performance Certificate) measures the energy efficiency of a home and is influenced by factors such as insulation, heating, lighting, and window performance. Older rooflights with poor insulation can negatively impact a home's EPC rating.

By upgrading rooflights, homeowners can:

Reduce U-values of existing rooflights

Improve overall thermal performance

Reduce heating and cooling costs

Increase property value

Table: Comparison of Typical Retrofit Options

Retrofit Option	Typical U-Value (W/m²K)	Expected EPC Impact	Notes
Single-glass skylight	5.0	Negative	Common in pre-1980s homes; poor insulation
Polycarbonate dome replacement	3.0–4.0	Moderate	Reduces heat loss; improves durability
Double-glass retrofit skylight	1.8–2.5	Positive	High performance; suitable for most roofs
Triple-glass retrofit skylight	1.2–1.8	Very Positive	Best insulation; reduces condensation risk
Secondary glazing addition	2.0–3.0	Moderate	Ideal for heritage buildings

Note: Values are indicative and depend on frame material, installation, and glazing type.

Retrofit Skylight U-Values: Choosing the Right Specification

When planning a retrofit, understanding retrofit skylight U-values is critical. For energy-efficient performance in older homes, aim for:

Double-glazed units: U-values between 1.8–2.5 W/m²K

Triple-glazed units: U-values between 1.2–1.8 W/m²K

Frame improvements: Reduce thermal bridging with insulated frames or thermal breaks

In addition to U-values, consider:

Solar Heat Gain Coefficient (SHGC): Controls the amount of solar radiation entering the home.

Visible Light Transmission (VLT): Ensures adequate daylight without excessive heat gain.

By selecting rooflights with optimal U-values, homeowners can achieve energy savings while maintaining comfort and natural light.

Practical Considerations for Older Homes

Retrofitting rooflights in older homes requires careful planning, especially when dealing with heritage properties or roofs with structural limitations. Some key considerations include:

Structural Support: Older roofs may require reinforcement to accommodate larger or heavier units.

Weatherproofing: Ensuring proper flashing and sealing is essential to prevent leaks and maintain insulation.

Heritage Restrictions: Some listed buildings may limit changes to external appearances, necessitating discreet solutions such as secondary glazing or conservation-style skylights.

Orientation and Placement: Proper placement maximizes daylight and minimizes unwanted solar gain.

Replacing Polycarbonate Domes: A Step Towards Modern Efficiency

Polycarbonate domes were popular in the 1970s and 1980s due to their light weight and low cost. However, these domes have several drawbacks:

High thermal transmittance

Prone to scratching and yellowing

Shorter lifespan compared to glass alternatives

Replacing them with modern double-glass or acrylic units can significantly reduce heat loss, improve light quality, and enhance the home’s aesthetic. Modern units often feature:

Low-E coatings to reduce heat transfer

Argon gas fills for better insulation

Laminated or toughened glass for durability

This retrofit is one of the most effective methods for improving skylights energy efficiency in older homes.

Long-Term Benefits of Rooflight Retrofitting

Retrofitting rooflights is more than a cosmetic upgrade; it offers long-term advantages:

Energy Savings: Reduced heat loss and improved insulation lead to lower energy bills.
Comfort: More consistent indoor temperatures and reduced drafts enhance comfort.
Property Value: Energy-efficient upgrades are attractive to buyers and can increase resale value.
Sustainability: Lower energy consumption reduces carbon footprint, contributing to eco-friendly living.

Steps to Plan a Successful Retrofit

Audit Existing Rooflights: Identify current U-values, glazing type, frame condition, and any signs of leaks or condensation.
Set Goals: Determine desired improvements in EPC rating, comfort, and energy savings.
Select Products: Choose skylights that meet modern thermal performance standards and fit structural requirements.
Hire Experienced Installers: Proper installation is critical to achieve maximum energy efficiency.
Test and Maintain: After installation, check for air tightness, leaks, and functionality. Regular maintenance prolongs lifespan.

Conclusion

Retrofitting rooflights is a highly effective way to improve energy efficiency in older homes. By replacing outdated polycarbonate domes, upgrading glazing, and optimizing frames, homeowners can reduce heat loss, increase comfort, and improve EPC ratings. Modern skylights combine the benefits of natural light with energy efficiency, making them a worthwhile investment for any home.

Whether you aim to enhance sustainability, cut energy costs, or simply make your home brighter and more comfortable, retrofitting rooflights is a practical and impactful solution. By understanding skylights energy efficiency, retrofit skylight U-values, and methods such as replacing polycarbonate domes, homeowners can bring older properties into the 21st century while preserving their character.