Not sure whether to go for a framed or frameless rooflight?
Our helpful guide explains the difference between the two so you can make the right choice for your home.
What Are Frameless Rooflights?
Frameless rooflights are designed to look like “glass-only” openings, with less visible framework from above and (often) a cleaner sightline from below. In many systems, the insulated glass unit is bonded to an upstand/kerb using structural silicone, rather than being held in a fully visible surrounding frame.
In real terms, “frameless” usually means:
- The aesthetic priority is an edge-to-edge glass look and a low-profile finish.
- Performance is driven heavily by the glass specification (glazing build-up, coatings, gas fill, spacers) and by the quality of the builder’s upstand and waterproof detailing.
A big reason homeowners choose frameless rooflights is to keep an extension or flat roof conversion looking clean and uncluttered, while still bringing in plenty of natural daylight and clear views of the sky. They’re particularly popular above kitchens, stairwells, hallways, and open-plan living spaces where natural light can completely transform the feel of the room.
What Are Framed Rooflights?
Framed rooflights incorporate a surrounding frame, most commonly aluminium, engineered as a complete unit that supports the glazing, manages interfaces, and provides a consistent finished edge.
A major advantage of many framed rooflight designs is the ability to include a thermal break within the frame. A thermal break is an insulating barrier inside a conductive metal profile that helps reduce heat transfer through the frame (limiting “cold bridging”).
In practice, framed rooflights often appeal when you want:
- A more defined perimeter and robust edge detail (useful where tolerances, kerb conditions, or roof build-ups are complex).
- A system designed around predictable interfaces and consistent performance across multiple unit sizes.
- Extra specification flexibility (e.g., privacy glass, solar control, self-clean upgrades, frame colour choices), depending on the product line.
Frameless vs Framed – Side by Side Comparison
| Consideration | Frameless rooflights | Framed rooflights |
| Overall look | Minimal “glass-only” appearance; very clean roofline | Defined perimeter; frame can be a design feature |
| Visible internal border | Typically reduced (depending on the system) | Typically more visible than frameless |
| How they’re commonly fixed | Often, structural silicone bonding to the upstand/kerb | Factory-built unit installs onto/with kerb details |
| Thermal strategy | Heavily driven by the glazing spec and upstand insulation | Often combines strong glazing with thermally broken frame options |
| Condensation risk management | Strong glazing + correct pitch/detailing matter | Thermal breaks and warm-edge glazing can help reduce cold bridging |
| Best-fit projects | Modern minimal extensions; clean sightlines | Projects needing robust perimeter detailing, pitch flexibility, or more frame options |
| Typical pricing tendency | Often cost-effective for a clean look (varies by spec/size) | Can be higher due to frame engineering/options (varies widely) |
Key Decision Factors
Design & Architectural Style
If your goal is a nearly invisible roof opening, especially from external viewpoints, frameless designs are commonly selected for their uninterrupted aesthetic. Manufacturers frequently position frameless/low-profile rooflights as a way to achieve a clean roofline with edge-to-edge glazing.
If your project suits a more defined architectural edge (or you want the frame to align with other fenestration colours/materials), framed rooflights can offer frame finishes and engineered perimeter detailing that are easier to coordinate across a broader build specification.
Natural Light Priorities
Roof glazing can deliver substantially more daylight than the same-sized vertical windows because of its orientation to the sky. Roof windows can provide at least twice as much light as the same-sized vertical windows under similar conditions (and more compared to dormers).
If maximising the visible glass area is a top priority, frameless-style rooflights are often chosen specifically because they reduce the visual presence of perimeter elements and keep the focus on the glazing.
Thermal Performance
Thermal performance is best approached as a combination of:
- Glazing U-value (lower generally means better insulation), and
- Frame thermal design (where relevant), and
- Edge-of-glass performance (spacers/warm edge), and
- Upstand/kerb insulation and airtightness.
A lower U-value indicates less heat transfer through a building element and therefore better insulating performance. Thermally broken frames help reduce conductive heat flow through metal framing systems. Warm-edge spacers are designed to reduce cold bridging at the perimeter of insulating glass units, helping reduce edge heat loss and condensation risk.
Budget Considerations
Budget is influenced by size, glazing build-up, coatings (solar control, privacy), and extras like self-cleaning glass, plus installation requirements and access.
On the Toughened Glass Systems range (ex. VAT), listed price bands vary by product family and size:
- Triple-glazed self-clean rooflight: £163.00–£619.00
- Flat roof skylight windows: £259.00–£2,800.00
- Framed flat skylights: £390.96–£3,309.82
- Framed rooflight TGS: £350.00–£2,733.20
Installation costs can be a meaningful part of total spend and typically vary by size, roof conditions, and access requirements.
Installation Environment
The right choice between framed and frameless rooflights often comes down to the practical details of the project itself. Factors such as the roof build-up, the pitch of the roof, and the overall site conditions can all influence which option will work best in the long term.
For flat-roof installations, achieving the correct pitch is particularly important. A slight slope helps rainwater run off the glass rather than pooling on the surface, which improves both drainage and long-term performance. Our team generally recommends a minimum pitch of around 5 degrees for flat rooflight installations. This helps prevent water from sitting on the glass and also allows coatings such as self-cleaning glass to function effectively.
Real-World Considerations
In reality the long-term performance of a rooflight has a lot to do with things like the type of glazing, how well condensation is controlled, whether it’s got safety glass, and how well the whole unit is put in and sealed.
One thing that really makes a difference to homeowners is a self-cleaning glass. If it’s been spec’d right, this sort of glass has a special coating that reacts to daylight and breaks down dirt on the surface. Plus, when it rains, the water spreads out across the glass rather than forming drops, and that helps wash away the loosened dirt. Over time this can really cut down on the amount of scrubbing you have to do, especially on rooflights that are hard to get to.
Condensation is also a big worry with roof glazing. This usually shows up at cold spots around the edge of the glass or in the metal frame bits, but modern rooflight designs are starting to tackle this problem. They’ve got thermal breaks in the frames and warm-edge spacers in the glazing unit. These design features stop heat from transferring and reduce that cold bridging effect which helps keep the temperature inside a bit more stable and reduces the chance of condensation forming.
Toughened Glass System Products
Frameless Rooflights
Triple Glazed Self-Clean Rooflight
Price (ex. VAT): £163.00–£619.00 (includes an inc. VAT reference on-page).
What it is: A frameless-style rooflight using triple glazing and self-clean glass, positioned as suitable for flat or pitched roofs. Toughened Glass Systems lists a centre U value of 0.9 W/m²K, and notes a warm-edge spacer/argon-filled build in its technical information.
Benefits: self-clean glass, triple glazing, UV protection, reduced condensation risk, and a listed 20-year manufacturer warranty, plus fast delivery lead time noted as 1–3 working days in most areas.
Flat Roof Skylight Windows
Price (ex. VAT): £259.00–£2,800.00 (includes an inc. VAT reference on-page).
What it is: A bespoke flat rooflight range with glazing and finish options (double/triple glazing; clear, blue, grey, opaque, solar control; optional self-clean), positioned to flood interiors with daylight while keeping a low-profile presence typical of flat roof glazing.
Benefits and key specs:
- Standard double-glazed units with a centre pane U-value of 1.1 W/m²K, argon-filled for improved thermal performance and manufactured in line with relevant glass and IGU standards.
- Triple glazing option available, achieving a centre pane U-value of 0.9 W/m²K for enhanced insulation.
- Optional glazing upgrades include self-cleaning glass, privacy glass options, and tinted or solar control glass to help manage glare and solar gain.
- Designed for installation onto a timber kerb, with guidance on recommended upstand height and minimum roof pitch to support effective water run-off.
- Lead times typically range from 2 to 5 working days for certain standard configurations and sizes, with longer manufacturing times for bespoke specifications.
Framed Rooflights
Framed Flat Skylights
Price (ex. VAT): £390.96–£3,309.82 (includes an inc. VAT reference on-page).
What it is: A framed flat rooflight with a powder-coated aluminum frame (standard noted as RAL 7016), described as thermally broken, and specified with a laminated inner pane for added safety.
Benefits and key specs:
- Centre pane U-value of 1.1 W/m²K, supported by a thermally broken frame design to help improve overall thermal efficiency.
- High-performance glass construction, featuring a toughened outer pane, argon-filled cavity, and a laminated Low-E inner pane to enhance insulation and safety.
- Recommended minimum roof pitch of 5° to support effective water run-off and reduce the risk of water pooling. A maximum pitch recommendation also applies to this product type.
- Fast delivery available, with certain standard sizes typically delivered within 2–3 working days.
Framed Rooflight TGS-2
Price (ex. VAT): £350.00–£2,733.20 (includes an inc. VAT reference on-page).
What it is: A custom framed rooflight line (sold on the TGS product page; often referenced as “TGS-2” via the product URL/variant) offering glazing choices (double or triple), glazing finishes (including solar and privacy options), and optional self-clean.
Benefits and key specs:
- U-value options available – 1.2 W/m²K for double glazing or 0.7 W/m²K for triple glazing, depending on the configuration selected.
- Argon-filled glazing units with Thermal Super Spacer technology to help improve thermal efficiency and overall insulation performance.
- Aluminium frame construction with an integrated thermal break, designed to reduce heat and cold transfer and help minimise the risk of condensation.
- Security-focused design, with positioning aligned with PAS 24 requirements and manufactured in accordance with relevant glass and insulated glass unit (IGU) standards.
- Suitable for roof pitches up to 45°, with guidance provided on maximum external kerb sizing for correct installation.
- 10-year manufacturer’s warranty for added reassurance and long-term product reliability.
Contact Toughened Glass Systems
For assistance choosing between framed and frameless rooflights, or to confirm sizes, glazing options (solar control, privacy or self-cleaning), delivery lead times, and suitability for your project, our team is happy to help.
You can contact us via:
- Telephone: 0203 633 3224
- Email: [email protected]
- Opening hours: Monday to Friday, 9am–6pm
Contact us today.