Infusing a bathroom or hallway with natural light can be a challenge. If the room is defined by interior walls, adding a window is impossible, and installing a framed skylight may be a bigger project than you want to tackle. However, if your house was built after 1970, it probably has trusses framed 24 in. OC. With 24 - in. - OC framing, you can install the largest - diameter tube skylight on the market with very little mess and complete it in one morning.
The Sun Tunnel is a 22 - in. - dia. flexible - tube skylight that allows you to easily bend light around attic obstructions without using elbows or other connectors. It's a complete roof - to - ceiling system, which means it has an integral shaft, so you don't have to build one.
Club Member Jim Richardson installed the 22 - in. Sun Tunnel (it's also available in 14 - and 20 - in. - dia. models) in his 70 - sf bathroom. Now there's so much natural light that every time Jim or his wife walks past the bathroom, they reach in to turn off the light. What a nice problem to have.
Space requirements
There are a couple things to consider before you begin. First, there must be attic space above the room where you want the skylight. Second, your roof and ceiling framing must be 24 in. OC to accommodate the 22 - in. - dia. skylight.
Jim's situation is a bit unusual: the house doesn't have trusses. However, the roof is framed 24 in. OC, while the ceiling is 16 in. OC. We accommodated the ceiling opening by removing a short section of one ceiling joist and reframing it with headers, creating a 32 - in. opening. We couldn't have done this with truss framing; altering a truss compromises its structural strength.
Check the attic for major obstructions. A small jog or bend in the tube won't affect the light intensity too much. Two or more gradual bends in the tube will greatly reduce the amount of light that it admits.
Finally, the roof should face south for maximum light. A west - facing roof is a suitable second choice.
Probing and cutting
Determine the location for the skylight in the ceiling. Locate the ceiling joists either by using a stud finder or by tapping on the ceiling. A hollow sound indicates a stud cavity; a solid - sounding rap indicates a ceiling joist. Center the location side to side and front to back in the stud cavity.
Once you have determined the spot, push a straightened metal coat hanger up through the ceiling into the attic. The hanger should be about a foot long so it penetrates the insulation and is easy to locate.
Now it's time to venture into the attic. Moving insulation creates a lot of dust. A disposable Tyvek suit keeps the fiberglass dust off clothes and skin; a dust mask and safety glasses are musts.
Be careful where you step when you're in the attic. Stand on boards or small pieces of plywood laid perpendicular to the joists.
Locate the protruding coat hanger and pull back the insulation. Center the location in the joist cavity. If you need to adjust the position, push a 16d nail through the ceiling from the attic side to mark the new location.
Determine the most direct path for the tube between the ceiling and the roof. Use a plumb bob to establish the straight drop. Although we had a horizontal support in our path, the Sun Tunnel duct is flexible, so making this slight bend was no problem.
Once you know where the hole in the roof should be, drill a hole through the roof sheathing and shingles from the attic. A 3/4 - or 1 - in. - dia. spade bit makes a hole that eliminates having to make a plunge cut.
Back in the bathroom, locate the centerpoint for the skylight. The instructions tell you simply to put the ceiling ring against the ceiling and use it as a template. We found this to be a bit cumbersome, especially for one person working alone. Instead, we used four tick marks as guides. Measure one radius - length of the ring (11 in., or half of the circle's diameter) from the nail. Make tick marks at 3, 6, 9 and 12 o'clock. Line the ceiling ring up with the marks and trace around the ring.
Leave two 1 - in. lengths of uncut drywall opposite each other on the circle when cutting the ceiling hole. These tabs keep the circle from dropping and tearing the drywall paper. Support the cutout in the center and make the finish cuts. Save the ceiling cutout to use as a template for marking the roof. Finally, install the ceiling frame ring.
Center the drywall cutout over the hole in the roof and trace around it. Cut out the area with a reciprocating saw or jigsaw. Pry up the shingles around the hole so the flashing has an unobstructed path beneath the roofing material.
We discovered that despite what the instructions say, it's easier to make sure the roof frame flashing slides into place without obstructions before you attach the tubing to it. The assembled unit is too unwieldy for test fitting. Once you know the frame and flashing slip in cleanly, begin the process of assembly and installation.
The key to the installation is attaching the duct to the skylight top frame before you install the frame. It would be extremely difficult to attach the duct with the frame already in place on the roof. Plus, you would have to spend more time in the attic.
Turn the top frame upside down and slip one end of the flexible tubing over the stainless steel ring that's attached to the underside. It's designed for a snug fit, so expect some resistance.
With a screwdriver and pliers, bend the four precut tabs over the tubing that is over the ring. Make sure you catch two or three of the steel ribs or "skeleton" of the tube with the tabs. They're sharp, so wear work gloves. Secure the tubing to the ring with the supplied PVC tape.
The instructions tell you to measure down through the roof opening to the attic side of the ceiling to find the length of the tube. We found an easier and more accurate way to get this measurement. Set the partially assembled unit over the hole and let the tubing drop down into the opening in the ceiling. Send someone into the bathroom to gently pull the tubing down through the hole, getting it as taut as possible. More light will reach the room if the tube is smooth. Mark two or three spots on the inside of the tube where its bottom will touch the attic side of the ceiling once it's cut to fit. After marking, gently push the tubing back into the attic.
Back on the roof, pull the entire assembly out of the hole, being careful not to tear the tubing. Cut off the excess. A utility knife easily cuts through the tube film, but you'll need diagonal or side cutters to cut the steel rib. The steel skeleton is in a coil or spring configuration, sort of like a giant Slinky. To make a straight cut on the tubing, you must jump over the steel rib and continue cutting the film. If you follow the path of the coil, you'll spiral - cut into the main shaft area of the tube. If this happens, you'll need to buy a new length of tube because you won't be able to repair the damage.
Once you've cut the tube to length, attach the stainless steel lowering ring to the end of the tubing in the same manner as you attached the tubing to the roof frame. Pull the cut tubing over the ring about halfway and secure it with PVC tape.
Getting the entire unit into position and sliding the flashing under the shingles is easier with a helper. He or she can keep the tube compressed until the flashing slips up under the shingles far enough so that the tube drops cleanly through the hole. With the unit in place, secure the flashing to the roof with roofing nails. The lower edge of the flashing will be on top of the roof shingles. The weight of the shingles secures the upper portion of the flashing. Seal each nail head with a dab of silicone caulk. Fasten the plastic dome to the top frame with the four rust - resistant screws.
Finishing Touches
The tube and lowering ring should be hanging near the hole in the ceiling. Carefully pull the steel ring tight against the inner lip of the ceiling frame ring. Secure the steel ring to the ceiling frame with the other four rust - resistant screws provided.
The final step is to assemble and install the diffuser panels. The Sun Tunnel comes with either a single or a dual diffuser system. The dual diffuser design is for skylights installed in colder climates. The prismatic diffuser goes in the lower slot in the gasket, the clear diffuser in the upper slot. A single - diffuser Sun Tunnel uses only the prismatic diffuser.
To get the diffusers and gasket into place, flex the entire assembly slightly and push it up through the opening. It goes in a lot easier than you might think. Lower the assembly onto the ceiling frame. Finally, use a blunt - bladed tool to work the lower ball section of the gasket out and over the entire perimeter of the ceiling frame to seal out moisture that could get into the tube.