Some homeowners regard glass windows set into the roofline as a luxury—the construction equivalent of a whirlpool hot tub in a bathroom or an outdoor kitchen on the patio. But skylights or roof windows are much more than a luxury, especially in regions that receive limited natural light, or with house construction where there is a limitation in wall area available for windows.
- In a second-story living space tucked beneath sloped rooflines, the presence of skylights may spell the difference between a bright, friendly space and a murky cave.
- In a home built between closely adjoining neighboring houses, skylights may be the best solution for introducing good natural light into rooms.
- In a one-story house build built with an open-concept floor plan, skylight shafts can bring much needed natural light into the center of large spaces.
Homeowners considering some form of glass set into the roofline can sometimes be confused by the various terms they encounter. It doesn't help when window manufacturers do not use the terms with any kind of consistency. For some, the terms skylight and roof window are entirely synonymous, while for other manufacturers, the differences are notable and important.
While there are precise structure definitions that distinguish skylights from roof windows, in the modern building trades, there are fairly common distinctions made:
- Skylight: A skylight is a fixed window set into the roofline. It may incorporate venting options, but the window itself does not open. In Europe, this type of window may be called a rooflite.
- Roof window: A roof window actually opens usually with a pivoting awning-style mechanism. It may even incorporate window screening, in much the same way as an awning-style window set into side walls. Some manufacturers, however, call this type of window a venting skylight.
- Light shaft: This term refers to a structural adaptation in which a walled shaft passes through between roof trusses or joists to link a room ceiling to a skylight or roof window. This shaft is sometimes called a chase. This is often the construction used in one-story homes, where a horizontal opening in the ceiling is connected to the roof-mounted window by a framed and finished shaft. The framing required by a shaft can add considerably to the cost of a skylight.
- Tube window: This is a simplified and inexpensive form of a light shaft, in which a small bubble dome window set into the roofline is linked to a lower ceiling by means of a flexible reflective tube. A tube skylight is normally used for small spaces to provide outdoor light to a small bathroom, closet, or laundry room. This is a very inexpensive option.
Skylight/Roof Window Options
There are nearly as many options for windows set into the roofline as there are for windows in walls. While operating mechanisms are somewhat more limited (you rarely find sliding windows or double-hung style used in roofs, for example), you have the same options for glazing and glass. Some types of roof windows are operated by remote control motors—which is essential if you want a vented window set high above in a light shaft.
Glass for roof windows and skylights is typically made from highly shatter-resistant glass, since these windows may be subject to impact from hail or falling tree branches. Beyond this, you'll have options for single, double-, or triple-pane glass, reflective coatings, gas-filled chambers between glass panels, and all the other options common with traditional wall windows.
Just as with traditional windows for walls, you have options for how to install roof windows or skylights. They can be installed yourself, by the window company, or by a traditional carpenter or general contractor.
- Homeowner Installation: If your skylight is small enough to fit between two trusses or rafters, your installation job will be vastly easier than if you need to cut away trusses or rafters. Many roof manufacturers include detailed instructions that make this a job that a skilled DIYer can easily tackle. If you feel comfortable with basic carpentry, shingling, basic window installation, drywall work, and painting—the same skills that go into installing a traditional window in a side wall—you can put in your own skylight or roof window. For motor-driven skylights, you’ll need electrical experience, too. DIY skylight installation is not a project that lends itself to impulsiveness. Be sure to consider your strengths and weaknesses before tackling a job that punches a hole in your roofline.
- Window Company: Any search for replacement windows will soon lead you to qualified professionals who can install skylights and roof windows. Pella, Marvin, and Andersen are among the big names in windows who can not only supply you with a skylight but also the qualified professionals to install it. The big downside here is that most window-only companies will do just that: install the window only. They will require a fully framed-out area in advance so that all they need to do is put in the skylight. Everything else—including the skylight shaft, where necessary—is up to you. For this reason, this is an expensive option. But it is also an option that pretty much guarantees a quality, warranty-backed installation.
- Carpenter or Contractor: Any general contractor, general carpenter, and even an experienced handyperson should be able to install your skylight. This option will be vastly cheaper than going with the window contractor. With this option, the contractor wears two hats: framing the area and also installing the skylight itself. A contractor will outsource activities to sub-contractors (notably, drywall work for the shaft). A carpenter/fix-it person, on the other hand, may do everything with him- or herself and perhaps a partner. The best advice here is to make sure to work with a contractor or carpenter based on a recommendation from someone who has used him or her successfully.
Limitations to Roof Windows and Skylights
Roof windows and skylights offer many advantages, but they aren't always a replacement for standard windows on side walls. Keep the following in mind:
- Windows are often required by building code because they provide egress (escape) in the event of emergencies. A skylight or roof window cannot always be used as a replacement for windows. Some manufacturers, however, offer roof windows with the spacing required to qualify as egress openings. There will, however, need to be a means for climbing down off the roof in order for the roof windows to meet the legal requirements for an egress window.
- The "solar gain" on a skylight or roof window is notable. This can be an advantage in cold climates, where the winter sun beaming down on the roof window can help heat a space. But it can be a distinct disadvantage in the summer or in warmer climates. Many skylights don't come with any kind of blind or method for blocking out the sun. This is an option that will usually cost you more.
Skylights and roof windows themselves are not prohibitively expensive, especially for DIYers who will be doing the work themselves. At one big-box retail center, recent costs for a fairly large roof window:
- Manually venting Velux roof window, 21 inches x 37 3/4 inches: $506
- Fixes Velux skylight, 21 inches x 46 1/2 inches: $399
These prices are not appreciably more than for good-quality wall windows designed for new construction.
The costs of having a carpenter or contractor do the work can add substantially to the price. Here are recent national averages:
- Cutting a hole in the roof and alter the rafter framing usually costs about $200. This cost can be considerably more for very wide windows that require cutting out rafters and reframing that area of the roof. Choosing windows narrow enough to fit between roof rafters or trusses is a good idea that will keep your costs manageable.
- Installing and flashing the window itself will cost $200 to $300 for homes with asphalt shingles, and 20 to 30 percent more for metal or tile roofing.
- Building a chase (shaft) from the skylight to the interior ceiling will cost $1,000 to $1,500.
- Repainting the ceiling beneath the skylight will cost at least $250 if you hire a pro.
Be aware that labor costs can vary considerably from region to region.