Not All Sun Tunnels Are the Same: What Should You Really Look For?

At first glance, many of these systems appear very similar. After all, they are all designed to bring natural daylight through the roof and into rooms or areas where conventional windows and rooflights are not possible.

However, our practical experience tells a different story.

At Techcomlight, we have specialised in natural daylight systems for more than 30 years. During this time, we have delivered thousands of daylighting projects for homes, commercial buildings, industrial facilities, agricultural buildings and infrastructure projects throughout the Netherlands, Belgium, Luxembourg, Germany, Poland, the United Kingdom and Ireland.

Over the years, we have seen new technologies emerge, develop and, in some cases, disappear again. Materials have changed, manufacturing methods have improved and the performance requirements within the construction industry have become increasingly demanding.

A solution that was considered suitable 30 years ago may no longer be the best choice for today’s buildings.

For this reason, we believe that a sun tunnel should not be assessed solely on its price or the diameter of its roof dome.

A Sun Tunnel Is Much More Than a Dome and a Reflective Tube

Many people compare sun tunnels based on their diameter or their claimed maximum daylight output.

This is understandable, but it only tells a small part of the story.

A complete tubular daylighting system is made up of many individual components. Together, these determine:

• how much natural daylight reaches the interior;
• how well the system is insulated;
• how effectively it limits air leakage and condensation;
• how long the system will last;
• how easy it will be to maintain;
• whether replacement parts will remain available in the future.

Important components include:

• the shape and material of the roof dome;
• any daylight reflector or light-capturing device inside the dome;
• the quality of the reflective light tube;
• the light transmission of the ceiling diffuser;
• the roof flashing or kerb;
• insulation around the tube and roof opening;
• the airtightness of the installation;
• the availability of replacement components;
• the product warranty;
• the environmental impact and durability of the materials used.

These details often make the difference between a daylighting system that performs reliably for decades and one that requires premature maintenance, repair or replacement.

Practical Experience Is Just as Important as Laboratory Data

During more than three decades in the daylighting industry, we have worked with a wide range of materials, production methods and system designs.

Some solutions have continued to perform extremely well over many years.

Others have been modified or replaced after practical experience demonstrated that a different material or construction method would offer greater long-term reliability.

For example, in the past we moved away from powder-coated steel flat-roof kerbs in favour of aluminium versions. We have also improved the construction of pitched-roof flashings, updated manufacturing methods and selected different materials based on what we learned from real installations.

We believe that product development should not stop when a product is first launched.

The experience gained from thousands of residential, commercial and industrial installations should continuously be used to improve the performance, durability and reliability of a daylighting system.

Look Beyond the Highest Claimed Daylight Output

A common mistake when comparing sun tunnels is to focus on just one technical value.

For example, products may be compared solely on the reflectivity of the light tube or the diameter of the roof dome.

Although both are important, neither value provides a complete picture of the system’s actual performance.

The final amount of daylight delivered into a room is determined by the complete system.

Factors that influence the overall daylight output include:

• the design of the roof dome;
• the presence and position of a daylight reflector;
• the reflectivity and durability of the light tube;
• the number and angle of any bends;
• the total tube length;
• the light transmission of the ceiling diffuser;
• the quality of the installation;
• the position and orientation of the system.

For this reason, we recommend asking for independently verified test results for the complete tubular daylighting system.

Relevant performance data may include the system’s total lumen output, visible light transmission or Light Transmittance, rather than only the reflectivity of an individual tube material.

The Components You Cannot See Are Important Too

Many of the most important technical differences between sun tunnels are hidden once the installation is complete.

An insulation blanket around the daylight tube, for example, can help create an airtight connection around the roof opening. It can also significantly reduce the risk of condensation forming around the system.

The choice of roof flashing or roof kerb is equally important.

A flat roof requires a different solution from a tiled pitched roof, a corrugated roof or an insulated composite panel roof.

Construction details such as the following may contribute to a longer service life:

• a seamless aluminium roof kerb;
• a suitable flexible flashing material for pitched roofs;
• a roof penetration designed specifically for corrugated or composite roof panels;
• mechanically pressed or sealed connections instead of joints that rely entirely on sealant;
• an insulated and airtight finish around the roof opening.

A high-performance reflective tube is of limited value when the roof penetration, insulation or internal connection is not designed and installed correctly.

A reliable daylighting system must perform as one complete building component.

Consider the Future of the Daylighting System

A sun tunnel is normally installed with the expectation that it will remain in place for many years.

However, one important question is often overlooked:

Will replacement components still be available in ten or twenty years’ time?

A damaged roof dome, a replacement ceiling diffuser or alterations to the building should not automatically require the entire daylighting system to be removed.

This is only possible when the supplier continues to provide individual components, technical support and service over the long term.

When comparing sun tunnels, do not only ask about the warranty period.

Also consider:

• whether individual components can be replaced;
• whether roof domes and ceiling diffusers are available separately;
• how long the manufacturer or supplier has been active;
• whether the product is part of the company’s core business;
• whether technical support is available locally;
• whether the brand is likely to remain supported in the future.

Long-term spare-part availability can have a significant effect on the total cost and usable life of the system.

A Warranty Is More Than a Number

A long warranty period may sound attractive.

However, the number of years stated in a brochure does not tell the complete story.

A warranty only has genuine value when the company behind the product is able and willing to provide support throughout that period.

It is therefore important to consider:

• the experience of the supplier;
• the organisation providing technical support;
• the availability of replacement components;
• whether installers and contractors can receive practical advice;
• whether daylighting systems are a core part of the supplier’s business;
• what is and is not included within the warranty conditions.

The combination of a reliable product, practical expertise, replacement-part availability and long-term service is often more valuable than the warranty period alone.

Sustainability Is Becoming Increasingly Important

The construction industry is changing.

In the past, purchasing decisions were often based primarily on price and thermal performance. Today, architects, contractors, developers, consultants and building owners increasingly ask about the environmental impact of construction products.

Subjects such as the following are becoming more important in specifications, tenders and building projects:

• Product Carbon Footprints;
• Environmental Product Declarations;
• embodied carbon;
• recycled and recyclable materials;
• local or regional manufacturing;
• transport distances;
• product life expectancy;
• repairability;
• end-of-life recycling;
• Total Cost of Ownership.

These considerations are particularly relevant to projects targeting lower embodied carbon, improved environmental performance, BREEAM certification or wider Net Zero objectives.

A sustainable daylighting solution should not only reduce the need for electric lighting during use. Its materials, production process, transport, expected lifetime, maintenance requirements and end-of-life options should also be considered.

We expect these factors to become even more important within the UK construction industry over the coming years.

Sharing Knowledge Rather Than Simply Selling Products

At Techcomlight, we believe that making the right choice starts with having access to clear and reliable information.

That is why we are publishing a series of technical knowledge articles exploring the most important aspects of sun tunnels and tubular daylighting systems.

Topics will include:

• why a daylight reflector inside the roof dome can be important;
• the differences between reflective tube materials;
• how an insulation blanket can help prevent condensation;
• how roof flashings and roof kerbs affect system durability;
• the differences between welded and seamless aluminium kerbs;
• long-term warranties and technical support;
• the future availability of replacement components;
• Product Carbon Footprints and environmental performance;
• Total Cost of Ownership;
• how to compare daylighting systems objectively.

Our aim is not to tell architects, contractors or building owners which brand they should choose.

Our aim is to help them ask the right questions.

This allows a sun tunnel or tubular daylighting system to be selected that not only performs well today, but remains dependable, maintainable and fit for purpose in twenty or thirty years’ time.

Ultimately, the quality of a sun tunnel is not determined by one component or one impressive technical figure.

It is determined by how well all the components work together to create a durable, energy-efficient and future-ready natural daylighting system