Korniche roof lanterns explained: what actually matters when choosing one

Korniche roof lanterns installed on a flat roof extension, bringing natural light deep into the space below.

If you’re planning an extension or renovation and looking at roof lanterns, it’s easy to get distracted by photos, finishes, and marketing claims. In reality, the long-term success of a roof lantern comes down to how it’s engineered, how it installs, and how it behaves on a real UK roof — not how it looks on day one.

This guide explains what actually matters when choosing Korniche roof lanterns, and why they’re specified differently to many “adapted” systems on the market.

1. Not all roof lanterns are designed from scratch

A lot of roof lanterns sold in the UK are, in reality, adaptations of conservatory roof systems. They work — but they weren’t designed for the way modern flat roofs, warm deck build-ups, and contemporary extensions are put together.

Korniche roof lanterns are different. They’re a purpose-designed aluminium system, engineered specifically for flat roof applications rather than repurposed from something else.

Why that matters in the real world:

• Components fit together precisely

• Fewer installation variables

• Less reliance on silicone and on-site improvisation

• More consistent results, regardless of who installs it

For homeowners, that usually means fewer call-backs. For builders, it means less time spent making things fit that should already fit.

2. Aluminium isn’t about looks — it’s about control

Aluminium roof lanterns aren’t “better” because they look modern. They’re better because aluminium allows tight tolerances and repeatable manufacturing.

With Korniche:

• Structural strength is designed into the system

• Slim internal sightlines are achieved without adding unnecessary rafters

• Loads are managed through the frame, not pushed into the glass

That’s how you end up with more glass and less frame, without cutting corners on strength or performance.

Internal view of a roof lantern showing clean sightlines and natural light entering the space below.

3. Thermal performance is a system issue, not just glass

You’ll often see roof lanterns advertised on glass U-values alone. That only tells part of the story.

What actually affects thermal performance:

• The thermal breaks within the frame

• How the lantern interfaces with the roof build-up

• How seals perform after years of movement and temperature change

• Whether fixings create cold bridges between inside and out

Korniche lanterns use a fully thermally broken aluminium structure, designed to reduce cold bridging across the entire assembly — not just at the glazing.

That matters for comfort, compliance, and long-term energy performance.

4. Installation design is where most lanterns fail

Most roof lantern problems don’t show up straight away. They usually appear months later — often after the first proper winter.

The most common causes tend to be:

• Over-reliance on silicone

• On-site drilling or trimming

• Poor load transfer onto the upstand

• Inconsistent or rushed sealing methods

We see the same issues come up time and again when lanterns are chosen on looks alone.

Korniche lanterns are designed to be pre-engineered and pre-tensioned, allowing installation without cutting or guesswork. That’s why they tend to be favoured by builders who want a repeatable install, not a system that depends on who happens to be fitting it that week.

5. Roof lantern vs flat rooflight — choosing the right solution

A roof lantern isn’t always the right answer.

A flat rooflight installed flush to the roof surface, offering a low-profile alternative to a roof lantern.

As a general rule:

• Roof lanterns suit larger spaces where architectural impact matters

• Flat rooflights work better where clean lines or minimal sightlines are the priority

The right choice usually comes down to ceiling height, roof structure, how light needs to spread through the room, and how the space will actually be used day to day.

We cover this in more detail here:👉 Flat rooflight vs roof lantern: which is right for your extension?

6. Who Korniche roof lanterns are actually for

Korniche roof lanterns are typically specified by:

• Homeowners investing in long-term projects

• Builders who want predictable installations

• Extensions where quality matters more than shaving a small amount off the upfront cost

They’re not aimed at cheapest-possible refurbishments or systems where installers are expected to “make it work” on site.

That distinction matters — and it’s not always explained clearly elsewhere.

Final thought

Choosing the lantern is the easy bit. Specifying it correctly for your roof is what determines whether it performs long-term.

That’s where working with a knowledgeable supplier makes a difference. At The Plastics Shed, Korniche roof lanterns are supplied with guidance based on real-world installations — not brochure assumptions.

If you’re planning an extension and want to understand whether a roof lantern or flat rooflight is right before committing, a short conversation at this stage can prevent costly changes later.