Tubular Skylights Are No Bargain

I was startled to read your survey of tubular skylight products (“Daylighting – Part 2,”

EBN

Vol. 8, No. 10, October 1999), which made no mention of the quality of light produced. As a residential designer with extensive daylighting design experience in both remodel and new-build situations, I would never specify one of these devices and in fact have had cause to recommend their removal. The reason: too little light in all the wrong places.

Good daylighting design ensures the light is focused where it’s needed—a relatively easy task with well-placed skylights and windows, but near impossible with tubular “solar” lights. They produce dull, diffuse light, with none of the shading, modeling, excitement of true daylighting. Your photograph example showed this in fact: try working at one of those countertops in your own shadow! I have seen as many as six of these units installed in an unsuccessful attempt to brighten a dark, wood-panelled den (total cost: over $2,500) when the real fix would have been to simply paint the walls white and/or remove the dense shrubbery which had been allowed to obscure the windows. All of these tubes were in a vented attic situation and allowed substantial energy leaks, through radiation, transmission, and air leakage losses. The owners still found the room unusable in the daytime without artificial lighting.

Here’s one of the odd facts about artificial lighting: in badly daylit spaces you often need more of it in the daytime than at night, because of the contrast glare caused by poorly placed daylight sources. The retina contracts because of the bright surfaces at the perimeter of vision, making the task at hand harder to see, so more task-lighting is added to compensate. Similarly, installation of tubular lights can actually make the situation worse, and result in greater use of supplementary lighting, not less. Factor that into your environmental appraisal, and these devices begin to seem like very poor bargains indeed.

James Morgan

Carrboro, North Carolina

Editors’ response:

Thank you for this valuable warning. With good placement and enhancements like Vista’s prismatic light diffuser, some of these drawbacks can be mitigated, but we should have been more cautious in our review. Also, our comments on the energy performance of these products assumed that the tubes through an unconditioned attic would always be insulated, which is, apparently, not a safe assumption! —

EBN