The Light Tube
A tubular daylighting device (TDD) is also called a light tube. A daylighting system works by using a dome on the roof of a building to collect daylight. The light is then transmitted through the building to the room where it is required by the TDD. The tube has an interior coating of highly reflective material which conducts the light down the tube with minimal loss. The reflective nature of the inner surface of the tube allows it to bend and change direction without almost any loss of light. The tube runs through walls to the area of the building where the natural light is required. It terminates in a diffuser assembly or light fitting from which light is provided to the space. The fittings are available in a variety of designs to match most home styles.
The TDD is therefore at the heart of the daylighting system because it brings the daylight indoors, passing through walls and going around corners. It was invented in 1993 by Solatube International. Although many others have since entered the field, Solatube remains the world leader.
The inner surface of the Solatube TDD is made up of multiple coatings of proprietary materials that reject the undesirable ultraviolet and infrared light spectrums. There is also an aluminum substrate that allows any heat to be dissipated near the roof line before it can enter the building. This means that only visible light is carried through the tube to the interior. There is only a 0.3 % of light loss with each bounce off the reflective surfaces. This means that the tube can be of up to 50 feet in length and can be turned at 90 degree angles with only minimal loss of light. Because of this ability, it is possible to carry the light to even the most interior parts of a home.
The TDD is simple to install as it resembles normal ducting. It is surprisingly inexpensive. Elegant fittings are available to match any room décor. Once installed, there are no running costs. And perhaps equally importantly, it is a way to make a home green and environmentally friendly.