Solar Light Pipes [Everything You Need to Know]
Natural lighting is superior to artificial lighting in just about every way. It reduces our energy bills, carbon footprint and has a positive impact on our moods.
The only downside to natural lighting is that it’s not always as convenient as we’d like it to be.
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Many buildings simply don’t have windows, and those that do may not be oriented in such a way as to receive direct sunlight.
Therefore, designers and architects are constantly looking for creative ways to bring natural light into spaces that don’t have it.
One of the most effective and popular solutions to this problem is the use of light pipes or solar light piping. This technology involves the use of a system that collects natural light from outside of the building and redirects it indoors.
It is a great alternative to artificial lighting especially for spaces away from the building’s perimeter, and where traditional daylighting apertures cannot be installed.
What are Solar Light Pipes?
Solar light pipes, also known as light tubes, sun tubes, sun tunnels, or tubular daylighting devices (TDDs), are systems that collect natural light from outside of a building and redirect it indoors.
The system typically consists of several components including a high-efficiency optical element at the entry point on the roof, an insulated pipe that transfers the light, and an exit point on the inside of the building where light is delivered.
Solar light pipes work by channeling the sunlight along the pipe using total internal reflection (TIR), which occurs when light moves from one medium to another and is reflected along a surface between these two mediums.
The pipe’s housing directs the sunlight along the length of the pipe until it reaches a diffuser, which then channels that light into an interior space.
To achieve this, the internal surface of the pipe is made from highly reflective materials that allow light to travel along the length of it.
What are the components of a solar light pipe system?
A typical solar light pipe system consists of a solar collector on the roof that collects the sunlight by focusing it into a pipe with highly reflective internal surfaces.
When sunlight hits on the collector, it is focused into a beam and enters the piping system through an optical device that is used to direct the light into one end of the pipe.
The collector is protected with a tempered or laminated transparent cover from breakage, thermal stress, and water intrusion.
The pipe’s internal surface that transfers the light is made from a highly reflective material such as aluminum, and its exterior surface is typically protected by UV stabilizers.
Let’s take a look at all the components that make up a typical solar light pipe system:
Collector
The collector is the first part of a solar light pipe system. It is usually a dome-shaped structure that contains an optical element, such as a mirror or lens, to concentrate and direct sunlight into the pipe.
The collector is usually installed on the roof of a building, but may also be mounted to an exterior wall or other location that allows it to capture the most amount of sunlight.
Light Tube
The light tube is the part of the system that channels sunlight from outside a building, where it enters through a collector, to the interior of a building. It has reflective inner walls that allow sunlight to shine straight through it.
The tube can be rigid or flexible depending on its application. A rigid tube is made of plastic or metal, while a flexible tube is usually constructed from aluminum foil or reflective plastic that can bend and flex to provide desired installation position.
Diffuser
The final part of a solar light pipe system is the diffuser, which distributes natural sunlight evenly to an interior space.
The diffuser is the part of a system where light finally enters an interior space, and it diffuses the light to provide even illumination. It may be designed to tint the light, or have special coatings that change its color temperature.
Dimmer
A solar light pipe system may come with a pre-installed dimmer that allows adjusting the amount of light coming through a diffuser.
Dimmers can also be installed as a standalone add-on to an existing system. They are typically controlled via a wall switch or can be programmed to turn on and off as desired.
Light tube diameter & Space size requirement
There are different sizes of solar light pipes available, which are typically categorized by the diameter of their tubing. The below table shows how much of a space can be lit based on the tube’s diameter.
| Tube Diameter | Covered Surface Area |
|---|---|
| 10 inches | Covers 150-200 ft2 per tube |
| 14 inches | Covers 250-300 ft2 per tube |
| 21 inches | Covers up to 500 ft2 per tube |
| 29 inches | Best suited for Sports Halls and similar areas with floor-to-ceiling heights ranging from 16′ to 23′ (5m – 7m). |
| 39 inches | Best suited for factories and similar applications with a floor-to-ceiling height of up to 30′ (9m). |
| 59 inches | Suitable for much larger applications. |
The above values are only the best estimates for reference. The actual sizing of a light tube system is dependent on the environmental conditions, position, and height of collector installation, as well as the type and quality of the diffuser.
Light pipes are classified into two main categories according to their functionality of tracking the sun as it moves across the sky. Now let’s look at what they are and how they work.
Active vs Passive Light Pipes
There are two types of light pipe systems available on the market today when classified according to sun-tracking capability.
Active light pipes
Active light pipes use a tracking system that automatically follows the sun’s path and adjusts to optimize daylight.
These types of systems are equipped with sensors that detect available daylight. When sufficient daylight is detected, the tracking system moves into position to redirect it.
Tracking systems are usually equipped with a motorized drive that automatically adjusts the light pipe to the necessary position as daylight conditions change.
Passive light pipes
Passive light pipes are passive systems that do not track the sun. They rely on the natural movement of sunlight by means of a passive collector, which captures it from its fixed position and channels it to a diffuser.
These systems are the common choice for most applications because they are generally less expensive and easier to install. They also do not require any special mounting hardware or control systems which make them even more practical.
Passive systems are not as efficient as active systems since they do not use the full potential of available daylight.
They also require manual adjustment to maximize their effectiveness and efficiency, which can require some additional labor on the part of end-users.
That said, even passive systems are a good choice for supplementing or replacing artificial lighting since they can do a good job of bringing the daylight into large areas.
Do solar light tubes worth the investment?
Solar light tubes are worth the investment because they provide an opportunity to improve indoor environmental quality and reduce the energy demand for lighting without having a significant impact on a building’s design or construction budget.
They effectively supplement or replace artificial lighting in large areas. They can be quickly implemented in both residential and commercial building projects without requiring significant exterior changes.
Working with a well-designed diffuser, they provide even illumination to large areas with high ceilings and can be supplemented with artificial light to ensure adequate lighting in low-ceiling spaces.
Solar light tubes vs Skylights
Both skylights and solar light tubes work to bring daylight into indoor spaces, but the two systems work in different ways.
The main difference between solar light tubes and skylights is that the skylight brings daylight into the space directly without any conversion or control.
On the other hand, solar tubes don’t allow the direct entry of light into a space. They work by collecting daylight outside and redirecting it using lenses and reflectors.
However, this is not the only difference between the two systems.
Here are the most important factors to consider when choosing between a skylight and solar light tubes:
Light efficiency
Skylights are more efficient than solar light tubes because they bring daylight directly into the space.
They have a larger opening than solar light tubes and allow for more natural daylight to enter without any conversion.
Solar light tubes are designed with lenses that focus and direct daylight into a specific area and there is a loss of light due to the conversion and reflection processes.
Installation
The installation process for skylights usually requires making significant changes to a building’s exterior unless it is a new construction project.
To install a skylight, a large hole in the roof must be cut, and the skylight must be attached and sealed into the opening. This process is usually labor-intensive and may necessitate additional structural support, increasing installation costs and time.
On the other hand, solar light tubes can be easily and quickly installed without requiring significant exterior changes to a building’s structure or appearance.
Light control
Skylights generally don’t have any special light controls. On the other hand, solar light tubes can be equipped with a variety of lenses or reflectors to control the direction and intensity of daylight.
This allows for more precise light management in specific areas which can reduce indoor lighting costs and improve the quality of light.
That said, skylights can still allow for some light control with the use of blinds or shade screens. Combined with the correct positioning, skylights can be used to control daylight without losing any of its benefits.
Maintenance
The maintenance requirements for solar light tubes and skylights are similar. Both require regular cleaning to ensure that they are working properly and bringing in the correct amount of daylight.
Skylights may require periodic testing of their sealing and flashing systems if they are part of a ventilated roof system. This is usually not a concern with solar light tubes because they are not part of a roof ventilation system.
Light quality
Both skylights and solar light tubes provide high-quality daylight. However, skylights provide a more direct source of light that is not subject to any conversion or reflection processes.
Hence, skylights can provide more powerful illumination.
On the other hand, solar light tubes can be equipped with different types of lenses that allow for better control over daylight intensity and direction.
This can reduce the light intensity in certain areas to create a more comfortable lighting environment. Of course, skylights can also be equipped with adjustable shading systems.
Payback
The payback period for skylights can be significantly longer than that of solar light tubes.
This is because skylights are more expensive to buy and require significant changes to be made on the exterior of a building. They need special mounting hardware, flashing, or other exterior components which increases installation costs.
On the other hand, solar light tubes are a cheaper alternative to skylights and can be installed quickly. This also reduces installation costs and reduces the payback period.
Typical Uses
While both skylights and light tubes can provide a cost-effective way to bring daylight into large interior spaces, skylights are much less versatile than solar light tubes.
Since skylights require a permanent large opening to be made in the roof of a building, they are not an ideal solution for retrofitting existing buildings.
However, they are a good choice for new construction projects where the exterior of the building can be designed to incorporate a skylight.
On the other hand, solar light tubes can be installed in most building rooftops without compromising the integrity of a building’s structure.
If you are considering a light tube for your home, you will need to understand the advantages and disadvantages.
Solar light tubes have a number of key advantages over skylights, including the fact that they do not require a special window frame and offer greater energy savings.
Advantages of Solar Light Tubes
A light tube is a type of light source that is used to direct light into areas of a building where natural light cannot reach.
Room daylighting can be improved by combining the use of windows and light tubes. Light tubes transmit more consistent sunlight thanks to a multi-reflection system.
Disadvantages of Solar Tubes
Limited view
If you want to enjoy the view of an open sky, light tubes are not ideal. They only give access to diffused sunlight and do not offer a clear line of sight. For the best possible view, skylights are the best option.
Inadequate ventilation
Light tubes do not allow for natural airflow, which means that they are not the ideal choice if you want to make use of a warm or cool breeze. If you want to use the natural airflow of an open sky for ventilation, skylights are a more practical choice.
Condensation Issues
If not properly planned, light tubes can cause condensation problems. Because the light tube is an enclosed system with one end on the outside and the other on the inside, temperature differences can cause condensation to form.
This is why, if you intend to use light tubes for indoor daylighting, you should be aware of the effect they can have and plan ahead of time for condensation.
How much do solar tubes cost?
Solar tubes are available in a wide range of sizes, shapes, and styles. Prices can range from $500 to more than $1500 depending on the manufacturer, the model, and the features.
How long should a warranty last on a solar light pipe?
The majority of manufacturers provide a ten-year warranty. However, the warranty period for different components that makes up the system may vary.
Make sure to check the warranty period of each component before making a purchase, and if labor and installation are also covered under the warranty.
What type of tests do solar light pipes need to pass?
Manufacturers that want their light tubes to be used for illumination or daylighting need to have them tested and certified by an accredited agency.
In addition, the components that make up the light tube system need to be certified separately.
The following performance requirements must be met by completed light pipe system assemblies:
Air Infiltration Test
Air infiltration tests verify that air does not seep through and become trapped inside the system.
When tested in accordance with ASTM E 283, the light tube system must have an air infiltration rate of no more than 0.30 cubic feet per minute (cfm) per square foot aperture and a pressure delta of 1.57 pounds per square foot (psf) across the tube to pass this test.
Water Resistance Test
This test ensures that the light tube system is resistant to prolonged exposure to water.
If tested according to ASTM E 547, the light tube system should not allow uncontrolled water leakage at 10.5 psf pressure differential with a water rate of 5 gallons/hour/sf.
Fire Testing
Fire testing ensures that the light tube system will not contribute to a fire or make conditions more conducive for one.
The tests are performed should satisfy the relevant fire safety codes that are in place in the country of installation.
However, the below standards provide the basis for the required performance.
- When combined with the Dome Edge Protection Band, all domes meet the fire rating standards outlined in the 2006 International Building Code.
- Self-Ignition Temperature – greater than 650 degrees F, according to U.B.C. Standard 26-6. (Refer to ASTM D-1929.)
- Smoke Density – No more than 450 per U.B.C. 8-1 (See ASTM Standard E 84) in the specified use.
- Rate of Burn and/or Extent – Maximum Burning Rate: 2.5 inches per minute (62 millimeters per minute) CC-2 classification: U.B.C. Standard 26-7. (As per ASTM D 635)
- Rate of Burn and/or Extent – Maximum Extent of Burn: 1 inch (25 mm) Classification CC-1: U.B.C. Standard 26-7. (As per ASTM D 635).