Wednesday, August 18, 2010

Selecting "Solar Tubes" for Natural Lighting

Also known as tubular skylights, solar tubes are used to light a room with natural sunlight. You may also see these devices referred to as solar pipes, or light tubes, but officially, they're known as tubular daylighting devices (TDD).

A basic TDD consists of four primary components...
·      Dome
·      Flashing
·      Tube
·      Diffuser

Sunlight enters the device through the dome. The light is channeled through a highly reflective tube to an interior room of your home. But before it enters your room, it is "scattered" through a diffuser to create a soft light effect. The flashing is between the dome and the roof to prevent water from leaking into your home.

Rules of thumb for any tubular skylight:
·      The shorter and straighter the tube the better performance.
·      South or West facings are best in the Northern Hemisphere.
·      Look for higher reflective tubing.
·      There are two types of tubing used a multilayer film and an electrobonded tubing (multilayer film can delaminate over time from UV exposure).
·      Manufacturers tend to over estimate the square footage coverage, so when in doubt go for larger tube diameter.

We're planning to install TDDs in the hall bathroom,
and the entry between the foyer and the great room.
Should you get rigid or flexible tubing? The rigid shaft sun tunnel offers up to 3 times the light in a room than the flexible shaft model, because of the fact that the loss of light is minimal in the process. The highest individual transmittance recorded for a flexible tube stretched was 6.8%, which was less than one sixth of that for the rigid tube. The rigid sun tunnel is suitable for places that require direct and longer tunnel length, especially great for those areas with less sunlight or the North facing roofs, giving 98% reflectivity.

You can install both the tubes on roofs with slopes between 15 degree and 60 degrees, and the installation process requires only basic carpentry skills.

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