Roof Lanterns for Commercial and Residential Builds: A Trade Buyer’s Guide

Introduction

Roof lanterns are a staple specification item for roofers and builders working on both residential extensions and commercial refurbishment projects. The market is wide, the quality varies considerably, and the lead time catches out more projects than it should.

This guide covers the practical decision points when specifying a roof lantern — glazing material, profile, thermal performance, planning constraints — and explains how to order efficiently through a single trade supplier.

What Is a Roof Lantern?

A roof lantern is a raised, glazed superstructure that sits above a flat or low-pitch roof opening to introduce natural light and — where openable panels are incorporated — natural ventilation into the space below. They are most common over:

• Single-storey extensions on residential properties
• Open-plan kitchen and living areas in new-build houses
• Commercial reception areas, atria, and communal spaces
• Orangeries and garden rooms

Unlike a standard flat rooflight, a roof lantern creates a vertical glazed profile that dramatically increases the visible sky and daylight penetration. The difference in how a room feels is significant — particularly in single-storey rear extensions where the depth of the room limits window light.

Glass Roof Lantern vs Polycarbonate Roof Lantern — Which Is Right for the Project?

Glass Roof Lanterns

Toughened and laminated glass panels offer:

• Superior optical clarity — no yellowing or UV hazing over time
• Better thermal performance through low-e coatings and argon/krypton filling
• Higher acoustic insulation values
• Premium aesthetic for residential and high-specification commercial applications

The trade-off is weight and cost. Glass lanterns are heavier, require appropriate structural support, and carry a higher material cost than equivalent polycarbonate units. However, for any project where the client is paying for a premium finish, glass is the correct specification.

Polycarbonate Roof Lanterns

Polycarbonate panels offer:

• Lower overall weight — easier to handle and install, particularly at height
• Impact resistance — relevant for applications in hail-prone or exposed locations
• Cost efficiency — lower material cost than glass equivalents
• Good thermal performance in multiwall configurations

The limitation is long-term clarity. Polycarbonate is susceptible to surface scratching and UV degradation over time, though modern UV-coated polycarbonate performs considerably better than older materials. For commercial applications where aesthetics are secondary to function and durability, polycarbonate remains a practical choice.

Rule of thumb: residential applications with a visible interior ceiling — specify glass. Commercial or industrial applications where function outweighs aesthetics — polycarbonate is often the more practical and cost-effective choice.

Thermal Performance and Building Regulations

Roof lanterns are subject to the same thermal performance requirements as any other rooflight under Part L of the Building Regulations (Conservation of Fuel and Power). The key metrics are:

• U-value: The overall thermal transmittance of the unit. Part L1A (new dwellings) and Part L1B (existing dwellings) set limiting values for rooflights. As of the 2021 revisions, the limiting U-value for new rooflights in new-build dwellings is 1.2 W/m²K. Always check current approved documents, as these values are subject to revision.
• Total roof area: Part L limits the proportion of total roof area that rooflights can cover. Check the current approved documents for the applicable limit — typically expressed as a percentage of the total floor area or total roof area depending on building type.
• Solar gain (g-value): In commercial applications under Part L2, solar heat gain through rooflights is a regulated consideration. High g-value rooflights in south-facing applications can significantly increase cooling load.

Always confirm the U-value and g-value data from the product data sheet before submitting building control information. RamSpec AOV product pages include technical specifications to support building regulations submissions.

Planning Considerations for Roof Lanterns

For residential extensions under permitted development, the planning position on roof lanterns is generally favourable — rooflights that do not project more than 150mm above the roof plane are typically permitted development. Roof lanterns, being raised structures, may fall outside this, particularly in conservation areas or properties subject to Article 4 directions.

For commercial projects, planning requirements vary by local planning authority. Early engagement with the planning department on proposed rooflights is good practice, particularly for listed buildings or properties in sensitive locations.

As a supplier, RamSpec AOV does not provide planning advice. Confirm the planning position with the relevant local planning authority before ordering.

Sizes and Configurations

Roof lanterns are available in a wide range of standard sizes — typically from 600mm x 600mm up to 4000mm x 2000mm and beyond for bespoke configurations. Standard sizes carry shorter lead times than bespoke manufactured units.

Configuration options typically include:

• Fixed (non-opening) — light only, no ventilation
• Opening ridge vent — manual or electrically operated, for natural ventilation
• Integrated AOV opening — certified smoke vent functionality (note: this converts the lantern into a SHEV component requiring EN 12101-2 certification)

For projects where the roof lantern also forms part of the smoke control strategy, confirm that the specific unit carries EN 12101-2 certification. A standard openable roof lantern does not substitute for a certified AOV.

Ordering Roof Lanterns Through RamSpec AOV

RamSpec AOV Solutions supplies roof lanterns and rooflights from Brett Martin (Mardome), Ventlux, and Vent Trade (Vent Engineering) — available to order online at ramspecaov.co.uk.

All orders:

• Pro-forma payment — cleared payment required before despatch
• Direct delivery from supplier to site
• 10–15 working day lead time — build this into your programme

No account application, no minimum order, no need to go through a rep. Specify what you need from the product pages, pay online, and the order goes direct.

Plan for 10–15 working days from order to delivery. If the roofing programme is tighter than that, order as soon as the roof opening dimensions are confirmed — do not wait for the structural sign-off.

Summary

Roof lanterns are a standard specification item for roofers and builders working on domestic extensions and commercial refurbishments. Glass or polycarbonate, fixed or opening — the right choice depends on the application, budget, and thermal performance target.

Browse the full range at ramspecaov.co.uk. Products from Brett Martin, Ventlux, and Vent Trade — ordered online, delivered direct.