A small tube of sun

2 August 2010
OK, let’s launch straight into the fortnightly rant (thanks for inspiration Steven Fowle). This one regards skylights. Widely used, inserted willy-nilly into otherwise graceful rooflines, seen as a desirable bonus in any addition project.

It turns out the skylight is a deceptively poor source of light (and thus poorly named.) It does not transfer diffuse day light into a room well, but it sends sun in only at the time that it passes over that part of the roof. In addition there is a large space in the roof which is now of a reduced insulation layer, and may collect snow, ice and leak water. Finally, they can also create convective currents that result in condensation. So really we should call skylights “water-catching sky windows.”

As incongruous to the roofline, but of a much smaller footprint is the sun tube. Because of their domed construction, a sun tube (also called a solar tube) can actually gather light from all angles and provide a potent source of daylight. The dome actually serves to refract sunlight into the tube, where it is reflected down to a 10” opening with a diffuser in the ceiling. The tube can be run several feet between the room wanting light and the rooftop penetration. I first saw these installed at Heather Parker’s über-efficient home in Portsmouth New Hampshire, and was amazed at how well they worked.

So… I had to put one in the bathroom this weekend. Aside from some struggle with the reflective aluminum tubing it was a small beer. Here’s how easy it is:

Nail up through the roof and trace the hole’s diameter














Cut out the hole














Mount the flashing “boot”














Install metal tube / Cap with the dome














The result is the still unfinished, and currently undiluted light source seen streaming down here (once the insulation happens, I’ll be able to finish it with a covering.) I’m also tempted to just leave it open as is – granted how strange and beautiful the view is up there. Note that the tube is mounted on the north-east pitch of the roof.