Everything Homeowners Need to Know About Roof Lanterns

When you build or extend a single-storey flat-roof room, one of the challenges is natural light. A flat roof covers the space, so you lose the open sky above. That’s where a roof lantern comes in: it’s a glass-topped structure that sits on top of the flat roof and brings light from above into your extension.

Whether you’re adding an extension, upgrading a room, or just doing a renovation, one of these can make a big difference. This article walks you through what they are, why they’re popular, the materials used, how to choose wisely, and what benefits you get.

What is a Roof Lantern?

A roof lantern is an architectural feature that sits on top of a flat roof (often for a single-storey extension) and acts like a miniature glazed roof. It’s not just a window in the roof—it’s a framed, multi-sided structure (often with triangular or trapezoidal glass panels) that brings in light from above. Wikipedia+1

These are especially useful when you want a “proper” room, not just a conservatory. Unlike typical conservatories (which can be cold in winter and hot in summer), a modern flat-roof extension with a lantern can give you good insulation and everyday usability.

Why People Choose Roof Lanterns

There are a few strong reasons why a roof lantern is becoming a preferred option:

• Light – They flood the space with natural daylight from above, which can lift mood, reduce artificial lighting and make a room feel larger.

• Architectural feature – A lantern isn’t just functional; it’s a design element. It can become a centerpiece in rooms such as kitchen extensions or living areas.

• Value addition – A good quality lantern can enhance the appeal of the extension and increase the value of the property when done well.

• Better alternative to conservatories – As conservatories fall out of favour, more homeowners want solid, usable extensions with a flat roof plus a glazed top. Lanterns fill that gap.

Material Choices: Timber, PVC/UPVC, and Aluminium

When selecting a roof lantern, one of the first big decisions is the frame material. Each has pros and cons.

Timber

• Traditional look, especially suited to period homes.

• Natural insulation properties: timber doesn’t conduct heat as much as metal.

• But it requires more maintenance: painting or finishing is needed, and timber can be more expensive.

PVC / UPVC

• Generally the more cost-effective option.

• Available in many colours and finishes.

• However, PVC expands and contracts more with heat, so for large spans it may suffer warping or twisting over time.

Aluminium

• Strong yet lightweight. Because it’s rigid, profiles can be slim which maximises glass area (more light).

• Very low maintenance: aluminium doesn’t rot and is generally more durable.

• A slightly higher cost compared to PVC, but better long term performance.

Performance: Thermal Efficiency, Glazing and Details You Should Check

Choosing the material is important, but what really makes or breaks a lantern is the performance features built into it. Here are the details to watch out for:

Thermal efficiency

• No matter how good your glazing is, if the frame and connections are weak, you lose heat. Some lanterns have thermal breaks (often polyamide strips) between metal profiles to reduce heat transfer.

• Check the U-value (a measure of heat loss). A good lantern will provide this for the full assembly, not just the glazing alone.

Glazing and insulation

• Double (or even triple) glazing: between the glass panes there may be a gas like argon to reduce heat loss.

• Spacer bars: cheaper systems will use aluminium spacers (which conduct heat); better ones use composite/plastic spacers that reduce heat transfer. gfdhomes.co.uk

• Solar control: the glass might also have coatings to reflect heat back in winter or reject excess heat in summer.

Build standards & guarantees

• Look for manufacturing standards and certifications (for example in the UK something like a BBA certificate) to be sure the product meets independent test criteria. gfdhomes.co.uk

• Check lead times: you don’t want building works delayed because the lantern is on long lead time.

• Guarantee: The paint finish, the frame materials and the glazing should have a warranty.

What to Ask and Consider Before Choosing a Lantern

As a homeowner, when selecting a roof lantern it’s helpful to ask your supplier or installer the following questions:

• Is the frame material suitable for the span and glass you want? Large glass areas need strong frames with minimal sagging.

• What is the full U‐value of the completed lantern (frame + glazing + assembly)?

• Does the frame include a thermal break?

• What are the maintenance requirements? (especially for timber)

• Are there custom sizes and colour finishes available?

• What is the expected lead time?

• Can you view a sample or showroom unit?

• What guarantee or warranty is provided?

• How will the lantern integrate with the roof structure and upstand?

Advantages & Disadvantages of Roof Lanterns

Advantages

• A dramatic increase in natural light and sense of space. gfdhomes.co.uk+1

• Adds style and architectural interest to the home.

• Often enhances the value and appeal of an extension.

• Modern designs with good insulation and glazing minimise heat loss.

Disadvantages / Things to Watch

• Some budget models may have poor insulation or thermal bridging which can cause heat loss.

• Maintenance: timber options especially will need periodic repainting or stain.

• Higher cost compared to a standard flat roof light or skylight.

• Cleaning may be more involved given their position on the roof.

• If the build or installation is poor you risk leaks or condensation.

How a Roof Lantern Fits in a Flat Roof Extension

If you’re building a single‐storey extension with a flat roof and you want to bring in daylight, a roof lantern works like this:

1. The flat roof is built with a slight fall (so water drains away).

2. On the flat roof you build an upstand or kerb (a raised edge) that the lantern sits upon.

3. The lantern frame is fixed to that converted kerb/roof structure, glazed with high quality insulated glass.

4. Internally you get daylight pouring into the room from above, which makes the space bright and airy.

Because conservatories are less popular (often being too cold in winter or too hot in summer), this approach gives you a fully usable living area all year with the benefits of overhead glazing.

What Homeowners Should Budget For

When budgeting for a roof lantern in a flat roof extension keep these in mind:

• The lantern cost itself (frame + glazing + installation) varies widely depending on size, material, colour and quality.

• Frame material choice (timber vs aluminium vs PVC) makes a big difference.

• The roof build must integrate the lantern: that might mean reinforcement, proper upstand, waterproof detailing and good insulation.

• Glazing specification matters: high performance glass will cost more but save on running costs.

• Additional costs: installation access, scaffolding, structural works if required.

Summary: What to Look for in a Great Roof Lantern

• High quality frame material (aluminium is a very good balance of strength, durability and slim look)

• Thermal break built into the frame to reduce heat loss.

• Excellent glazing: double/triple glazed, argon filled, good spacer bar.

• Proper build quality and certification.

• Good warranty and proven track record.

• Integration with a well-built flat roof (good upstand, waterproofing, insulation).

Final Thoughts

Adding a roof lantern to a flat roof extension is a smart way to bring in natural light, create a standout design feature, and potentially add value to your home. The material and build quality matter a lot — you’ll get performance and longevity only if you pick a lantern that’s built well and installed properly.