Enjoy the Sun and the Stars Without the Drips

A skylight can transform a dark room into a bright and welcoming space. Trouble is, some skylights let in drops of water along with the rays of sunlight—water that can cause unsightly damage or even mold issues if the water finds its way into ceilings or walls.

Here’s what you need to know before you have a skylight installed…

SELECTING A SKYLIGHT

It typically costs $1,000 to $2,000 to purchase a two-foot-by-four-foot skylight and have it professionally installed—more if it’s an especially complex installation or you choose a skylight with high-end options. Don’t try to save money by buying a low-end skylight or installing a skylight yourself (unless you have extensive experience)—the risk for leaks is just too high. If your budget is tight, there are smarter ways to save—more on that below.

What to look for in a skylight…

The Velux brand name. In my experience, no other manufacturer can match Velux’s reliability and overall quality. (I have no financial interest in Velux.) Velux skylights are sold at Lowe’s and The Home Depot among many other locations (VeluxUSA.com).

Multiple panes of glass with argon gas in between. These are more energy-efficient than single-pane skylights and much less likely to allow water drips due to condensation—home owners who think their skylights leak sometimes actually are experiencing condensation.

Helpful: Spraying foam insulation between the outer edge of the skylight frame and the wood framing of the roof during installation can help prevent condensation, too.

Never install any skylight made from translucent plastic rather than glass. These invariably are low-quality.

no more leaky skylights ABuilt-in blinds. There likely will be times when the sunshine coming in through your skylight causes problems. The light might shine in your eyes when you try to take a nap on a couch or shine on the TV screen, making it hard to see. It also could overheat the room on a hot day. For an extra $100 to $200, you typically can get a quality skylight that includes blinds. It can be very difficult to add blinds after a skylight has been installed—the aftermarket skylight-blind kits tend not to work well—so it’s worth spending this extra money up-front. If the skylight is not easily reached, select remote-control blinds.

Helpful: Some remote-control blinds are solar-powered. This eliminates the cost of running electrical wires up to the skylight. If the blinds are installed by the end of 2016, it might make them eligible for a solar power tax credit ­under the American Recovery and Reinvestment Act of 2009. This credit would be worth 30% of the cost of purchasing and installing the blinds. Your contractor should be able to provide a bill that breaks out the cost of the blinds from that of the skylight itself. The manufacturer’s website will provide details if its solar blinds are eligible.

TWO MONEY-SAVING STRATEGIES

There are ways to cut skylight costs without ending up with a low-quality, leak-prone product…

Skylights that don’t open. A “fixed skylight”—one in which the glass is fixed and cannot be opened—can cost hundreds of dollars less than a “venting” skylight of the same quality. They’re a smart way to save money because most home owners do not open venting skylights very often anyway.

Exception: It might be worth paying extra for a venting skylight in rooms that get extremely hot in the summer…and/or in bathrooms that have moisture or mildew issues. If you do opt for a venting skylight, a remote-control venting system is the best choice if the skylight is difficult to reach—those long poles used to crank open manually operated venting skylights are awkward and frustrating. A remote-controlled venting system powered by small solar panels can eliminate electrician’s bills and make the entire skylight eligible for the 30% federal tax credit mentioned above. (Sample savings: An average of $850.) Solar-powered blinds often are an option on a solar-powered venting skylight.

no more leaky skylights BThe tubular alternative. Tubular skylights, also called light tubes, don’t provide a window to the sky like a traditional skylight. Instead, they feature a rooftop dome that collects sunlight…a “diffuser” on the interior ceiling that distributes sunlight throughout the room below…and a reflective sheet-metal tube connecting these two components. This brings a surprising amount of natural light into a room for a reasonable price—often for $500 to $800 installed. Solatube is the leading brand and a good choice…Velux makes high-quality tubular skylights, too.

Tip: Have the metal tube of the tubular skylight wrapped in R-15 or R-19 fiberglass insulation. This reduces energy loss and the risk for condensation.

Tubular skylights make sense if…

  • The ceiling of the room you wish to brighten is many feet below the roofline. With a traditional skylight, this would require the construction of a long shaft—which would increase installation costs and decrease the area lit.
  • Structural elements in the roof make it impossible to position a traditional skylight where you would like. A tubular skylight’s tube can be routed around trusses and other impediments.
  • The room contains expensive rugs or furniture. Tubular skylights are unlikely to cause UV damage.
  • The room is a long hallway. For the same price as one traditional skylight, you could add two or three tubular skylights, which will do a better job illuminating a long, narrow space.

HAVING A SKYLIGHT INSTALLED

Installing skylights is a specialized job. You want someone who has installed the particular brand of skylight many times before. Ask stores that sell the brand of skylight you choose to recommend someone to do the installation. The skylight manufacturer’s website also might provide installer recommendations.

If your goal is to bring the maximum possible amount of sunlight into your home, the south or southwest side of your roof generally is best—assuming it is not obstructed by tall trees or buildings. The north side of a roof gets the least direct sunlight in the Northern Hemisphere, so a skylight placed there generally will not let in as much light.

It may be possible to reduce costs and increase the light that a skylight lets in by positioning it just above an exterior wall rather than higher up on the roof. The distance between a home’s exterior roof and the ceilings of the rooms below tends to be shortest near where the roof meets the home’s exterior walls and greatest near the middle of the home, where attic headroom is most substantial. The shorter this distance, the shorter the shaft that must be constructed for the skylight, reducing labor costs and increasing the amount of light in the room. This is not an issue if the home has a flat roof or a cathedral ceiling.

An experienced skylight installer can safely cut through rafters—the beams directly beneath the exterior roof—by reinforcing neighboring rafters. But if your roof is supported by trusses—that is, there are angled wood “webs” in the attic providing additional support to the rafters—these should not be cut. Doing so could cause major structural problems. It might be necessary to adjust the position of the skylight to fit between trusses. Trusses typically are positioned 24 inches apart, so a 22.5-inch-wide skylight should fit.

HOW TO FIX A LEAKY SKYLIGHT

If you can safely climb up onto your roof, there’s a good chance you can fix a leaking skylight. Leaks typically develop when small cracks or gaps form between the skylight and the roof.

First, clear away any debris that has accumulated against the top edge of the skylight. It could be causing water damming.

Next, carefully scan along the edge of the skylight’s frame for any cracks or gaps between the frame and the flashing (the strips of metal that provide protection where the skylight joins the roof). Remove old caulking or roofing cement you find between the flashing and the skylight frame if it seems to be cracking or crumbling, then reseal using polyurethane-based sealant. This costs a bit more than roofing cement, but it’s less likely to crack.

If the leaks continue, install a rain diverter. This is a long L-shaped piece of metal positioned on the roof slightly above the skylight to steer rainwater away. (See TodaysHomeowner.com/Installing-A-Rain-Diverter for details.)

If this fails, it is to time call in a roofing pro or skylight repair specialist.