Why are sun tunnels better than skylights?

There is a quality of life you get with natural light that artificial lighting just can’t fake. That’s why skylights and sun tunnels (or light wells) are so popular. Living in a naturally lit space improves moods, it saves energy on lighting, and it connects us to the outdoors.

At Ecohome, our experience shows that sun tunnels (with all their names such as tubular skylights, light wells or sun tubes) are a much less problematic way to achieve this than traditional roof window-style skylights.

It is often said about skylights that it’s not about ‘if’ a skylight will leak, but ‘when’ it will leak. And even worse, is that beyond having ‘actual’ leaks, sometimes when it looks like a skylight is leaking, it may just be condensation, but no matter where a drop of water comes from, it can wreak havoc in roofs and walls.

Even though they always bring with them durability issues, there is no escaping how dramatically a skylight can change the feel of a room. I actually still remember the first time I saw a skylight as a kid, it was in a friend's finished attic space, and that space was so impressive to me I can still remember it 30 years later. He went up several levels of cool to me just because of it.

There is something about light from overhead that changes the feel of a space, and we are strong proponents of any home design feature that makes living spaces more enjoyable and welcoming.

Let's explore why sun tunnels are our preferred method for overhead natural lighting, and why they often outshine their larger, more problematic cousins, the traditional skylights or Velux style roof windows.

Sun tunnels (with all their names such as tubular skylights, light wells or sun tubes) are a much less problematic way to achieve natural light in darker rooms in homes
Sun tunnels, tubular skylights, light wells or sun tubes, whatever you want to call them, are a much less problematic way to achieve natural light than traditional roof window-style skylights - Image - Velux

Why natural light in homes matters so much

Access to natural daylight is vital to human mental health. It boosts productivity, reduces eye strain, and helps regulate our sleep cycles. Sun tunnels are a really effective way to deliver daylight deep into spaces that traditional windows can't reach, like hallways, bathrooms, or even from a roof all the way to a basement. Let’s see your skylight do that!

Unlike traditional skylights, sun tunnels have minimal roof penetration, less heat transfer, and significantly reduced risk of common skylight problems. They are a focused, efficient solution for targeted light delivery into the heart of homes, and here’s how they work:

Understanding sun tunnels: simple and effective 

A sun tunnel is a straightforward, highly efficient system for free light delivery without significant energy loss or the risk of overheating a well-insulated home. It consists of three main components:

The dome (roof level): unlike the square flat surface of a typical skylight, sun tunnels have a clear, durable dome on your roof that captures sunlight from all angles. It's designed to withstand weather and collect maximum light while staying relatively low-profile and discrete.

The reflective tube: This is the core of the system, and the way it transfers light so far. A highly reflective, mirrored metal tube extends from the dome on the roof down to wherever in your house you are bringing light. It goes easily through an attic space whether that is a vented or unvented ceiling. The reflective tube can be either rigid or flexible, here are the pros and cons:

sun tunnels, tubular skylights, light wells or sun tubes come in rigid and flexible versions - but rigid sun tubes bring in far more light
Sun tunnels, tubular skylights, light wells or sun tubes come in rigid and flexible versions - but rigid sun tubes bring in far more light than the flexible versions that bounce light around and back out.

Rigid vs. flexible sun tubes -the efficiency difference:

For maximum light output and efficiency, rigid sun tubes transfer light much better and further – and not enough guides on sun tubes out there stress this difference enough.

Rigid reflector tubes have a smooth and highly reflective interior surface, usually consisting of a polished aluminum or some other sort of proprietary reflective film, with reflectivity ratings as high as 98% to 99.7% per bounce rate. This means very little light is lost as it travels down the tube.

Flexible sun tubes, on the other hand, for ease of install are typically made from corrugated, metallic-coated plastic or foil. This "accordion" structure can make it easier on installers to get around obstacles and corners, but you lose a lot of light as it bounces off countless tiny ridges and valleys.

For a mental picture, all you need to do is imagine the difference between trying to reflect light with a mirror and trying to reflect it with crinkled tin foil. What happens with the flexible tubes is that they even reflect light back up the tube.

The tangible result of using the ‘easy to install’ flexible sun tubes means you will lose a significant amount of light over a typical run compared to using rigid sun tubes. And the longer the run, the worse it is.

Independent testing indicates that a rigid sun tube can deliver anywhere from 2 to 10 times more light than a flexible tube of the same size and length. For anything but the shortest and most direct runs – meaning a few feet at most – using a flexible tube may completely defeat the purpose.

Choosing a tube diameter: Sun tunnels come in various diameters, for residential use that’s commonly 10, 14, or even 21 inches. And as you may suspect, larger diameter sun tubes deliver more light. So think about the space you are trying to light when choosing the tube size.

The diffuser lens: the interior surface of the sun tunnel that you see on your ceiling can further diffuse the light if that is the look and function you’re after. The interior lens scatters light evenly into the room and creates a soft, consistent glow. So that is another feature to think about when shopping for one.

Comparing sun tunnels to traditional skylights: An Ecohome perspective

Based on our experience and general mission to promote durable construction practices, and despite the fact that we love the look, we have never been big fans of including skylights on roofs. All of us love visiting homes with skylights but you won’t find us cutting into our own roofs to install one.

As covered in our guide "Skylights: An Asset or a Liability?" These larger Velux or Roto style units bring with them durability and maintenance concerns that sun tunnels largely avoid, making light wells and sun tunnels the better choice for home durability.

For maximum light output and efficiency, rigid sun tubes transfer light much better and further
For maximum light output and efficiency, rigid sun tubes transfer light much better and further and not enough guides on sun tunnels stress this difference enough

What is better about sun tubes over skylights:

  • Minimized risk of water leaks: The smaller the roof penetration and the simpler the flashing system, the lower the risk of water leaks. Traditional skylights have large openings, and operable skylights (the ones that open) can have complex mechanisms and are tougher to seal, so they are notoriously prone to develop leaks over time. Sun tunnels, with their small, circular, and often factory-sealed roof mounted dome units, drastically reduce this potential for water ingress problems.

  • Superior thermal performance (reduced unwanted heat loss & heat gain): A large pane of glass in your roof is a significant thermal bridge, even more so if your roof is super insulated. In winter, traditional skylights in roofs can be a substantial source of heat loss that drives up heating bills. In summer, they can contribute to excessive solar heat gain, overheating your home and increasing air conditioning costs. Sun tunnels, with their insulated tubes and smaller apertures, intrinsically minimize heat transfer intelligently. This keeps your home warmer in winter and cooler in summer, a critical factor for true energy efficiency and especially in areas with large seasonal differences like Quebec, the Canadian interior and the northern US states.

  • Eliminating condensation issues: Due to the large temperature differential across their big glass panes, in colder weather traditional skylights often get chronic condensation, leading to drips, potential water damage and wood rot, and mold growth around the frame, all the same problems that condensation on windows can cause, only worse because the drip is from above. Traditional skylights often become a cause of worry for homeowners – is it condensation? Are my skylights leaking? Is my roof leaking? Is that condensation on the outside, inside, or inside my skylight? The sealed nature of the tube virtually eliminates condensation worries and roof leak fears at the ceiling level.

  • Minimal structural impact: Installing a large traditional skylight often requires significant and expensive framing alterations of your roof design. Whereas the dimension of standard light wells lets them fit easily between existing rafters and roof trusses, whether they are spaced at 16” or 24” centers.

  • Reduced glare and UV damage: Large, direct overhead light streaming through from traditional skylights can cause uncomfortable glare and contribute to the fading of furniture and flooring due to UV exposure. Sun tunnels inherently diffuse light more evenly across the ceiling, providing a soft, natural glow that minimizes glare and UV impact, protecting your home's interiors.

For these reasons, while traditional skylights have that nice view of the sky, and particularly the stars, the downsides for us outweigh those advantages. We’d rather step outside to see the stars if it helps prevent roof leaks.

Energy efficiency: there is less heat loss with sun tunnels than skylights

Sun tunnels are designed for energy efficiency, making them a natural fit for Ecohome’s principles – and that’s why we like them! That and not liking the expense, mess and hassle of fixing skylights, which seems to be the inevitable fate of most of them. 

What we see as the advantage of sun tubes over skylights:

  • Minimal thermal bridging: Their small roof penetration and often insulated tubes drastically limit the surface area for heat to escape or enter. This is even more important in terms of roofs, which should be the highest insulated part of the home.

  • Airtightness: With fewer complex seals and a smaller opening, sun tunnels are generally easier to seal effectively, preventing heat loss and additional condensation concerns as warm humid air escaping homes leaves moisture in framing structures.

  • Passive illumination: Sun tubes provide abundant natural light, directly reducing your reliance on artificial lighting during the day and making interiors brighter and more uplifting. This is passive energy savings in its purest form.

Sun tunnels or sun tubes get rid of the condensation problems prevalent with skylights
Sun tunnels or sun tubes get rid of the condensation problems common with traditional skylights which can often cause damage to ceilings and walls.

Installation: sun tubes are simple and watertight

One of the significant advantages of sun tunnels is their relatively simpler installation compared to traditional skylights. This contributes to their reliability and reduces potential problems.

  • Less Invasive roof penetration: The small, circular opening required for a sun tunnel is less disruptive to your roof's integrity than a large, rectangular cut.

  • Minimal structural impact: Most sun tunnels fit neatly between existing roof rafters, often eliminating the need for complex and costly structural roof re-framing.

  • Integrated flashing: High-quality sun tunnels come with well-designed, integrated flashing systems specific to your roof type (pitched, flat, asphalt, metal, etc.). These systems are designed to create a watertight seal with your roofing materials. However, proper installation is still critical. Even with a simpler design, a poor installation can lead to leaks.

  • DIY vs. professional: While some very handy homeowners might tackle a sun tunnel installation, especially on accessible roofs and with basic kits, we generally recommend using an experienced and licensed contractor for the installation. They ensure the flashing is perfect, the seal is airtight, and the tube is correctly assembled for maximum light delivery and no leaks.

Maintenance: minimal effort, maximum light

Sun tunnels are largely maintenance-free, designed for fit-it-and-forget-it performance, especially in climates with some rain.

  • How to clean sun tunnels?: The exterior dome is typically designed to be self-cleaning with rain. The interior diffuser generally only needs a light dusting, but avoid abrasive cleaners that could scratch the dome or diffuser. Due to the fact that you aren’t actually looking out of a sun tunnel, it’s not particularly noticeable when they’re just a bit dirty.

  • Inspection: Periodically (e.g., annually) check the exterior dome for debris accumulation (leaves, branches) or any signs of damage and while there – give them a clean with a soft cloth and even give them a fresh coat of polish. From the inside, visually inspect the ceiling trim for any signs of moisture or condensation (though these are rare with sun tunnels).

  • How long do sun tunnels or sun tubes last?: A well-installed sun tunnel from a reputable manufacturer can last for decades, providing consistent, natural light with very few issues. Look for products with good warranties on all components from one of the larger brands to make sure you’re getting the best bang for your buck.

Finding the best sun tunnel / tubular skylight

For homeowners seeking effective natural light without the complexities, risks, and potential energy penalties of traditional large-pane skylights, sun tunnels (or tubular skylights / sun tubes) are a highly recommended, sustainable, and reliable solution. They deliver focused daylight where you need it most, efficiently and with significant peace of mind. Choose a quality product, ensure proper installation, and enjoy the bright benefits of your sun tubes for years to come.

When selecting a sun tunnel or sun tube, always look for products that are ENERGY STAR certified. This certification ensures the product meets strict energy performance criteria for your climate zone, confirming its ability to save energy and reduce greenhouse gas emissions. Pay attention to the U-factor (lower is better for insulation) and Solar Heat Gain Coefficient (SHGC) (lower is usually better to prevent summer overheating, though a high SHGC in winter can offer passive gain if managed with passive cooling strategies).

 

Now you know about the difference between sun tubes / sun tunnels and skylights and which is better. Find more pages about natural home lighting and resilient home design in these pages, and here in the Ecohome Green Building Guide: 

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