Window extensions

Sun Tunnel Buying Guide

Sun Tunnel Buying Guide

Brighten up areas of the home where natural light struggles to reach with a sun tunnel or two.

Sun tunnels, also known as light tunnels and sun tubes, are a practical, cost-effective way of introducing the benefits of daylight to spaces as small as cupboards and as big as bedrooms.

Healthier than artificial light and cheaper than roof windows, sun tunnels are an increasingly popular lighting solution for residential and commercial properties alike. 


Lightway sun tunnel Bohemian crystal dome

‌Should I Buy a Rigid or Flexible Sun Tunnel

Sun tunnels come in two distinct reflective tube designs, rigid and flexible. Both have their own advantages, it's up to you to decide which suits you best.



Rigid sun tubes provide sunlight with a direct path from roof to room, meaning less light bounces off the tube's surface and more makes its way into the room.

The pricier of the two tube types. Rigid sun tunnels can offer up to 20m of light distribution, meaning light can go a lot deeper into a room and brighten those harder to reach areas.

To help negate obstacles in the roof, Lightway’s adjustable elbow can be easily fitted to existing tubes, as can extension tubes to allow natural light to travel further.

World leading sun tunnel brand Lightway supplies rigid sun tunnels only in four different diameter widths. Rigid tunnels are also available from VELUX.

Rigid tubes of a pitched roof sun tunnel
flexible tube of a pitched roof sun tunnel





Flexible tubes are great for negating around obstructions in the roof space as they can be easily manipulated to bend around the existing building work.

Flexible sun tunnels are ideal for shorter distances and are the cheaper of the two options. The difference in price is mostly down to flexible tubes reflecting slightly less sunlight as rigid tubes.

Flexible sun tunnels are available from Sterlingbuild with either a 35cm, 45cm or 55cm diameter, in 3m tube lengths that can be easily cut to 2m.

VELUX’s flexible sun tunnels come with a diameter of 35cm and 2m long tube for slate and tile roofs.

What Size Sun Tunnel do I Need For My Room?

Deciding on what size sun tunnel you need all depends on room type. For the best results in medium to large spaces, we recommend installing either one or two bigger sun tunnels or a cluster of smaller tunnels.

sun tunnels installed in living area
large sun tunnel installed in kitchen area


Room Size- 0-4 m2

Room Type- Small rooms, cupboards, short corridors


Room Size- 4-10 m2

Room Type- Hallways, small bathrooms


Room Size- 11-15 m2

Room Type- Large hallways, stairwells, bathrooms


Room Size- 16-22 m2

Room Type- Kitchens, bedrooms, living rooms

Can Sun Tunnels Work on any Roof?

Yes, they can, and not just roofs either. As well as being compatible on both pitched roof and flat, sun tunnels are also available for installation on the outside of walls, exclusively from market leader, Lightway. Here is how.

 Flat Roof

 lightway sun tunnel on flat roof

Sun tunnels are available for all types of flat roof pitches, installed with a flashing and flat roof upstand.

Flashing and upstand come as standard with all Lightway products as part of a handy kit.

Flat roof sun tunnels are available from Lightway in five different diameter sizes, including the Lightway Maximus for large commercial buildings. All Lightway’s flat roof tunnels come with rigid tube.

In contrast, our own range of 35cm, 45cm and 55cm flat roof sun tunnels are available strictly with flexible tubes.

Offering both flexible and rigid options are VELUX, who manufacture a 35cm sun tunnel in both tube styles.

Pitched Roof

lightway sun tunnel of pitched roof

Lightway's pitched roof sun tunnel sizes are identical to their flat roof diameters with the exception of the Maximus.

Likewise, Sterlingbuild’s flexible pitched roof sun tunnels come in the same sizes as our flat roof sun tunnels and can be applied to both slate and tile.

VELUX’s flat roof offering consists of a 25cm and 35cm sun tunnel- one rigid and one flexible.

Remember to always bear in mind where the best place on your pitched roof is to position your sun tunnel.

Installing a light tunnel on the south-facing side of the roof will optimise the amount of natural daylight your tunnel can capture.

Through Wall

lightway through wall sun tunnel

Lightway’s unique through wall sun tunnels offer the perfect solution to brightening up even the darkest areas of the home.

Lightway is the only side wall sun tunnel manufacturer worldwide, creating a product that is ideal for basements and perfectly suitable for any room in the home.

Through wall tunnels work the same as regular sun tunnels in how they gather light. They can, however, transmit sunlight even further into the home than roof installations to distances up to 30m.

Like all Lightway products, the through wall sun tunnel comes with a 25-year guarantee for added cover and piece of mind.


Dome or Flat Glass Exterior Cover?

The exterior design of a sun tunnel is not just important for aesthetic reasons, but for overall performance too. Here is what you need to know.

Lightway sun tunnel with crystal dome


A sun tunnel with a dome cover protrudes above the roof with the dome and mounting unit sitting above the tiles. 

This more visual design turns the exterior of the sun tunnel into an attractive feature in its own right, with the fitting more visible from the outside.

Lightway manufacture all of their Crystal sun tunnel covers with high quality Bohemian crystal from the Czech Republic.

All of the dome covers on Lightway products are self-cleaning, meaning they won't deteriorate over time. Rounded domes to capture more daylight.


VELUX sun tunnel flat glass exterior pane

Flat Glass

Flat glass covers are a bit more inconspicuous than domes as a lot less of the product is visible from outside the home.

Flat glass covers sit almost flush with the roof and can be installed to match your windows or blend in effortlessly with your roof material.

Flat glass covers are not able to capture quite as much sunlight as rounded domes as some of light that hits flat panels is lost by means of reflection.

All VELUX and Sterlingbuild sun tunnels come exclusively with flat glass covers.



We have a number of additional accesories available at Sterlingbuild to enhance the scope and performance of your sun tunnel. Here are a few of our best.

lightway blue performance technology

Lightway Blue Performance Technology

Lightway’s innovative Blue Performance Technology add-on is a double or triple glazed insulation unit filled with argon gas, installed at the point of the building’s layer of insultation.

Blue Performance Technology helps evaporate condensation, thus stopping water leaks or mould forming on the ceiling.

This technology brings down the U-value of your sun tunnel to 0.6, making it suitable for Passive House standards.

For VELUX sun tunnels, condensation can be prevented with the installation of an underfelt collar.

adjustable elbow to make rigid sun tubes more flexible

Adjustable Elbows & Extension Tubes

To help you manoeuvre your rigid sun tunnel around roof construction, Lightway’s 45° adjustable elbow can be purchased to be used with any sun tunnel size.

Rigid VELUX and Sterlingbuild sun tunnels can also be made more flexible with the addition of adjustable elbows.

To expand the reach of your sun tunnel and illuminate rooms even further, extension tubes can be purchased for Lightway, VELUX and Sterlingbuild sun tunnels in various lengths.

For VELUX flexible sun tunnels, a 2m long extension can be added. The same is true for Sterlingbuild tunnels.

lightway electric dimmer for sun tunnels

Lightway Electric Dimmer

The Lightway Electric dimmer 220v is a piece of kit that allows you to take greater control of the incoming sunlight.

Decide how much light you want transmitted into your room by choosing between full sunlight, partly closed or fully closed.

In essence a blind for sun tunnels, Lightway’s electric dimmer is a practical supplement for sun tunnels, especially those installed in bedrooms and offices.

Everything you need to fit the dimmer comes as part of a kit, including aluminium tape and connection piece.