Step 1: Test all mechanical parts to be sure the windows open and close smoothly
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Photo 1: Check operating mechanisms
Open and close casement windows to test the smoothness of
the operating system. Test the latch system for even, tight
closure at the top and bottom.
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Photo 2: Check cleaning options
Test the tilt-out system on double-hung windows to make
sure you can operate it easily and remove the window for
easy cleaning. Make sure both sashes slide smoothly.
Windows are one of the most expensive features of your home, and you'll
be disappointed if they're drafty, don't open and shut easily, or break
down after a few years. Visit several window dealers and home centers
so you can test firsthand and compare as many types and brands of windows as possible.
The cranks on casement windows should turn
easily without binding or catching (Photo
1), and the locking latch should pull the
window tightly and evenly against the weatherstripping
from top to bottom. Double-hung
windows should slide snugly in their tracks, yet
not bind so that it's a strain to lift and lower
them. Sliding windows should glide on their
tracks without too much resistance.
Chances are you'll see and feel a significant difference
between lower- and higher-priced windows.
More-expensive windows generally have
heavier-duty, more-durable hardware and better
design, making them operate more smoothly.
They’re usually a better investment.
For easy cleaning, make sure you can reach all
glass surfaces. Test the tilt-out sash systems on
double-hung windows (Photo 2). Remove
both the upper and the lower sashes. If you can't
get them out fairly easily, you'll have to climb a
ladder to reach them—and you probably won't
clean them often.
Crank casement windows all the way to be sure
you can reach out and clean the exterior glass
from the inside. Some systems have a release that
allows you to rotate the glass for easier cleaning.
Step 2: Read the energy performance labels and compare the different glass options
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Photo 1: Compare energy labels
For the best energy savings and comfort, compare energy
labels on windows. A low U-factor is better in all climates.
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Photo 2: Triple-pane glazing
The most efficient
windows (low U-factor)
have triple panes, argon gas
between panes and several low-e
coatings. They're a good choice for
Windows account for about 22 percent
of the heating and cooling
losses in the average home. At a
minimum, buy windows with the Energy Star
label as shown to be assured of decent energy
savings. And consider windows with even higher
performance; they won't save you a whole lot
more on utility bills (yet!) but can make your
home a whole lot more comfortable. They'll
reduce cool drafts and condensation (see Step 4)
in cold weather and keep rooms from overheating
in hot weather.
To compare windows, read the NFRC
(National Fenestration Rating Council) energy-ratings
label that’s pasted on most units (Photo
1). Look for a low “U-factor” first. (Unlike
R-value, the lower the U-factor, the better.) This
is the rate of heat transfer through the window—glass and sash combined. Higher-performance
windows have a lower heat transfer rate,
making them more energy efficient, less drafty
and less prone to condensation. Double-pane
windows with clear glass generally have a U-factor
of about .40. Adding a low-e coating and
argon gas to the space between the panes lowers
the U-factor to about .35 (about a 15 percent
improvement). And triple glazing
(three panes, Photo 2) lowers the U-factor
to about .27. Windows with a low U-factor
are ideal for all regions. Note: For a true
comparison, you must check the labels for
windows that are about the same size.
To control overheating from direct
sunlight, look for a lower Solar Heat
Gain Coefficient (SHGC). The number
roughly represents the percentage
of the sun's heat that comes
through the glass. Low-e
coatings on the glass
can block most of
that heat. These
valuable in colder regions as well to block the late
afternoon summer sun on west-facing windows.
Tints also block the heat of the sun, but they
will obscure your view. Compare another number,
the Visible Transmittance, to make sure your
rooms remain light and bright and you retain a
good view. A .50 value is good; a higher value is
Chances are that the windows you'll see in a
showroom will have similar ratings, indicating
an adequate glass option for your region, but
usually not the best. You'll have to ask about
other options. They'll cost a bit more, but they're
usually worth it. One good Internet source to
compare energy ratings of various windows
(and brands) for your region is www.efficientwindows.org.
Step 3: Look for a long glass seal warranty
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Photo 1: Moisture fogging
Fogging between panes of this old insulating glass unit indicates
that the edge seal has broken. There is no fix except
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Photo 2: Glass label
Look for the manufacturer's name and manufacturing date on a corner of the glass unit.
Double-pane insulating glass is great for
comfort, convenience and energy efficiency,
but it has one weakness. If the
seal between the two panes deteriorates, moisture
will creep in and the glass inside will fog
up (Photo 1). There is no fix for this. You have to replace
the glass, typically costing $50 and up, plus
labor. Manufacturers know approximately how
long their seals will last (the failure rate) and
plan their warranties accordingly. Don't buy a
window with less than a 10-year glass seal warranty.
Better warranties will go up to 20 years.
Unfortunately, glass replacement is rarely
easy. Check the warranty (save your receipts!) to
see if it covers just the new glass, an entire new
sash—glass plus the wood,
vinyl or metal frame surrounding
replacement labor. Better warranties
transfer to new owners,
so if you recently bought a
home with fogged windows,
you might be in luck. Check
with the manufacturer.
Tip: The window brand and date of glass
manufacture is usually etched into a
corner of the glass or the edge spacer (Photo 2).
If you have trouble finding it, call
a window repair expert (search “Window
Repair” online or in your yellow pages).
Step 4: Bugged by condensation? Look for windows with “warm” edge spacers
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Condensation occurs around the edge of the glass first because of
greater heat loss through the glass's edge spacer.
Persistent interior condensation in cold weather
makes the air inside your house drier and causes
sash deterioration. It's an irritating problem,
because you often have to further lower your indoor
humidity to an uncomfortable level to protect your window
sash. Windows with a low U-factor (rate of heat
transmission) pay off here, because they cause less condensation.
However, even high-performance windows may
have a cold spot around the perimeter of the glass because
of the metal edge spacer, the rigid tube that separates the
two glass panes. That's where you'll see condensation first
occur. Some manufacturers address this detail by installing
“warm” edge spacers, that is, spacers that transfer less heat.
Finding this information can be difficult. The NFRC
label might include a condensation rating, but it's an
optional category that few manufacturers use. Ask the sales
staff or call the manufacturer to find out if it uses warm
Step 5: Check the exterior fit on replacement windows
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Check exterior trim sizes
Uneven trim widths resulting from a slightly different new
window size will require you to cut the siding back for a good
exterior trim appearance.
Your new windows may fit nicely into
the old rough opening and look great
from the inside, but they may not look
good from the outside. Usually you want the
exterior dimensions of the new window frame
to fairly closely match the old so that the exterior
trim remains the same (photo). If the
trim sizes change and look unbalanced, the windows
will look odd. You'll have to spend several
extra hours per window cutting siding and making
new trim, or pay a carpenter an extra $100 to
$200 per window to make the corrections. The
difficulty and cost go way up if your exterior is
stucco or brick.
Since new windows have to be ordered, you
won't have the opportunity to measure the new
unit itself. However, the window catalog usually
lists “unit” dimensions, which should be the
actual outside dimensions. The catalog may
include cross-sectional details of the top, bottom
and sides of the unit so you can see how it
fits into the opening. Sometimes one model or
brand will fit better than another. Some manufacturers
will make windows any size you want,
which may be a simpler and less costly solution
if you have a masonry or stucco exterior.
Step 6: Make sure you can find replacement parts
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Common window replacement parts
You can find common replacement parts like crank sets for
casement windows at many home centers. However, other
parts, like weatherstripping and the lift springs for double-hung
windows, are harder to find.
Depending on how much you move
them, such parts as crank arms,
counterweight springs and weatherstripping
will eventually wear out. Replacing
these parts is usually fairly easy, but finding the
replacement parts, especially 20 years from
now, may not be so easy. Many key
parts are not standardized; they're
unique to the brand and model of
window. So ask if the manufacturer makes spare
parts readily available. This is one advantage of
buying from manufacturers who have been in
business a long time. They'll probably be available
to supply spare parts years later. If you're
lucky, you can find parts through aftermarket
sources. One source is Blaine Window (www.blainewindow.com).