When it comes to introducing natural daylight into a flat-roofed space without the complexity of an opening mechanism, the fixed glass roof light is the product most homeowners and builders reach for first and for good reason. A well-specified fixed glass roof light delivers consistent, weatherproof daylighting with minimal maintenance, at a price point that suits most residential and commercial project budgets across the UK.
This guide covers everything you need to make a confident purchase - from how a fixed unit differs from an opening rooflight, through glazing specifications, sizing, installation, and what building regulations require.
What Is a Fixed Glass Roof Light and How Does It Work?
A fixed glass roof light is a sealed, non-opening glazing unit designed to sit within or on top of a flat or near-flat roof structure. Unlike an opening rooflight, it has no hinges, actuators, or ventilation function. Its sole purpose and it does it extremely well is to allow natural light to pass through the roof plane and into the space below.
Fixed units are the most straightforward rooflight product available. There are no moving parts to service, no motors to replace, and no seals around an opening sash to monitor for deterioration. For spaces where ventilation is provided by other means - mechanical extract, openable windows, or a separate ventilation strategy - a fixed glass roof light is almost always the right choice.
Browse the full range at our fixed rooflights collection, which includes both standard and custom-sized options across a range of glazing specifications.
Fixed Glass Roof Light vs Opening Rooflight: Which Do You Need?
This is the first question most buyers ask, and the answer is more straightforward than many expect.
|
Factor |
Fixed Glass Roof Light |
Opening Rooflight |
|
Purpose |
Daylighting only |
Daylighting and natural ventilation |
|
Moving parts |
None |
Hinge, struts, and actuator (electric) or handle (manual) |
|
Maintenance |
Minimal - no mechanism to service |
Annual check of hinge, seals, and actuator required |
|
Unit price |
Lower |
Higher - mechanism adds cost |
|
Lead time |
Standard sizes available for fast despatch |
Similar for manual; longer for electric |
|
Best suited for |
Spaces with alternative ventilation |
Kitchens, bathrooms, rooms without other openable windows |
|
Weatherproofing risk |
Very low — fully sealed unit |
Slightly higher — opening sash seal must be maintained |
Glazing Options for a Fixed Glass Roof Light
Double Glazed - The Standard Specification
Double glazing is the correct starting point for most fixed glass roof light installations in the UK. A double-glazed unit with a low-emissivity coating on the inner pane achieves a centre-pane U-value of around 1.0–1.2 W/m²K, which meets the requirements of Approved Document L for the vast majority of residential projects. It is the most cost-effective specification for new extensions, loft conversions, and flat-roofed additions.
Triple Glazed - High-Performance Projects
Triple glazing reduces the centre-pane U-value to 0.7 W/m²K or below, making it the right specification for Passivhaus schemes, highly insulated new builds, or any project where the roof is a significant source of heat loss. It also performs noticeably better on acoustic attenuation - a meaningful benefit in urban areas, near busy roads, or under flight paths. Triple-glazed units are heavier than double-glazed ones, which must be considered when designing the upstand and surrounding roof structure.
Solar Control Glass
South- and west-facing fixed rooflights are exposed to significant solar radiation during the summer months. Without solar control, this can cause uncomfortable overheating in the room below - particularly in well-insulated spaces with limited cross-ventilation. A solar-control coating reduces the solar heat gain coefficient of the unit while maintaining good visible light transmission, keeping the room comfortable without blocking the view of the sky.
Our flat glass rooflight and custom flat glass rooflight products are available across all of these glazing configurations, in both standard and bespoke sizes.
Building Regulations
Any new structural opening in a roof triggers a building regulations application, regardless of whether the rooflight is fixed or opening. The unit must comply with:
Approved Document L - Thermal performance. The glazing specification must achieve a U-value no worse than the limiting value for the roof element. In most cases, a double-glazed unit with a low-emissivity coating meets this requirement comfortably.
Approved Document K - Safety glazing. Overhead glazing in a building must be either toughened or laminated safety glass. Standard fixed rooflights are supplied with safety glazing as standard always confirm this at the point of order.
Planning permission is not usually required for a fixed rooflight on a flat-roofed extension within permitted development, provided the unit does not project more than 150mm above the roof plane. Conservation areas, listed buildings, and properties with restrictive planning conditions are exceptions - always confirm with your local planning authority.
Where Fixed Glass Roof Lights Work Best
Fixed rooflights are the right product for the widest range of applications: kitchen extensions, open-plan living spaces, hallways, loft conversions, and commercial fit-outs where daylighting is the primary goal and ventilation is handled separately. And if you are weighing up frameless versus framed options within the fixed category, the frameless flat glass rooflight guide covers the practical differences in full.
To explore the full range of fixed options or get a bespoke quotation, visit the rooflights collection or contact the team directly.
