The short, dreary days of winter are a good time to think about adding skylights
to brighten up dark rooms. Even small units make a big difference in the way
rooms look and feel.
There are many brands and several styles to choose from. But I advise my clients
to stay away from inexpensive units with plastic glazing. Although they are
cheaper initially, the bottom line is they don't last and many of them leak.
The better choice is a high-quality curbed skylight with energy-efficient glazing
-- and the factory flashing kit made for it. The kit won't add much to the
cost, but it will mean a leak-free installation.
Skylights come as venting units, which open, or as fixed units, which don't.
A venting unit might seem like a good idea, but it is inconvenient to open
and close when it's out of reach. In fact, many customers who order them later
tell me they rarely bother to track down the special rod needed to operate
their windows. So unless the skylight will be easily accessible, buy the fixed
unit and save yourself some money.
This even applies to putting a skylight in a bathroom. But it's essential
to make sure the room has adequate ventilation so condensation doesn't become
a problem. A vent fan for a small bathroom should provide 1 cu. ft. per minute
of air circulation per square foot of floor area, or about eight air changes
per hour.
Old-fashioned skylights were simply a single thickness of glass in a frame,
but today they come with laminated or tempered glass, and low-e and tinted
coatings to control heat transmission and UV radiation. Just like windows,
skylights are rated for their thermal efficiency by the National Fenestration
Rating Council (ratings are available at www.nfrc.org). You can compare the
U-values as well as heat and light transmission rates of various skylights.
Even though tinted glass is available, I generally recommend that you stick
with clear glass because it lets in more light. If intense sunlight does cause
too much heat buildup or begins to fade carpeting and furniture inside, add
a shade or screen.
Skylights are available in sizes that fit standard 16- or 24-in. on-center
framing. Adding a large skylight means that the installer will cut one or more
rafters (see illustration). This is not difficult when the roof is conventionally
framed -- rafters on the sides of the rough opening are doubled up and headers
are added at the top and bottom of the opening. But a truss roof is different.
Trusses are carefully engineered to carry roof loads, and modifying them in
the field is a bad idea. If your home has trusses, make sure the installer
sticks with units made to fit between roof members, or gangs several smaller
skylights together to create a larger window.
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