Windows
Windows provide our homes with light, warmth, and
ventilation, but they can also negatively impact a
home's energy efficiency. You can reduce energy
costs by installing energy-efficient windows in your
home. Some energy efficiency improvements to
existing windows can also help.
Here you'll find information about how to do the
following:
Selecting New Energy-Efficient Windows
When properly selected and installed,
energy-efficient windows can help minimize your
heating, cooling, and lighting costs.
Achieving improved window performance in your home
involves three steps:
Design
Consider your home's design and climate in relation
to the energy performance of windows.
Selection
Find windows that meet your energy performance
requirements.
Installation
Ensure proper installation of windows to maximize
their energy efficiency.
Improving the Energy Efficiency of Existing
Windows
You can improve the energy efficiency of existing
windows by doing the following:
Adding storm windows
Reduce air leakage and some heat transfer
Caulking and weather stripping Reduce air leakage around windows
Using window treatments or coverings
Reduce heat loss and/or gain
However, if your home has very old and/or
inefficient windows, it might be more cost effective
to replace them than to make these improvements.
New, energy-efficient windows eventually pay for
themselves through lower heating and cooling costs,
and sometimes even lighting costs.
Storm Windows
If you have old windows in your home, the best way
to improve your home's energy efficiency is to
replace them with new, energy-efficient windows.
However, if you're on a tight budget, a less
expensive option is to use storm windows. Some types
of storm windows are also a good option for those
living in apartments.
Even though storm windows add little to the
insulating performance of single-glazed windows
(that are in good condition,) field studies have
found that they can help to reduce air movement into
and out of existing windows. Therefore, they help
reduce heating and cooling costs.
Types of Storm Windows
Storm windows are available for most types of
windows. They can be installed on the interior or
exterior of the primary window. They range from the
inexpensive plastic sheets or films designed for one
heating season, to triple-track glass units with
low-emissivity coatings that offer many years of
use. Mid-priced storm windows may use glass, plastic
panels, or special plastic sheets that have specific
optical qualities. Those made of polycarbonate
plastic or laminated glass also offer a high degree
of resistance to breaking during storms and/or from
intruders.
For the most part, interior storm windows offer
greater convenience than exterior storm windows.
They're easier to install and remove; they require
less maintenance because they're not exposed to the
elements; and, because they seal tightly to the
primary window, they're more effective at reducing
air infiltration. Interior storm windows also are
often the best choice for apartments and houses with
more than one floor. If you can afford exterior
storm windows, you can probably afford some newer,
more energy-efficient windows, which will be a
better investment.
Glass pane types offer better visibility and longer
life than plastic pane types, but glass is heavy and
fragile. In general, plastics are most economical
for people with small budgets or who live in
apartments. However, while inexpensive and
relatively easy to install, they are easy to damage.
Plastic panels, such as Plexiglas and acrylics are
tougher and lighter than glass, but may scratch
easily. Some may turn yellow over time as well. Some
plastic films may significantly reduce visibility
and degrade over time when exposed to sunlight.
Wood, aluminum, and vinyl are the most common storm
window frame materials. There are advantages and
disadvantages to all types of frame materials.
Although very strong, light, and almost maintenance
free, aluminum frames conduct heat very rapidly.
Because of this, aluminum makes a very poor
insulating material.
Wood frames insulate well, but they weather with
age. They also expand and contract according to
weather conditions. Wood-frame storm windows
installed during the winter may not close easily
during the summer, and those installed during the
summer may fit loosely in the winter. They can also
be quite heavy and thicker than metal frames. This
can make storage difficult, reduce the view out the
window, and reduce the amount of natural light in
the room. Wood frames also require the most
maintenance. There are, however, aluminum- or
vinyl-clad wood frames that reduce maintenance
requirements.
Vinyl frames are usually made of polyvinyl chloride
(PVC) with ultraviolet light (UV) stabilizers to
keep sunlight from breaking down the material. They,
however, may expand and warp at high temperatures,
and crack in extremely low temperatures. Also, if
sunlight hits the material for many hours a day,
colors other than white will tend to fade over time.
Installation
No matter what type you choose, the storm window
frame must be hung square with the primary window
and sealed to the opening. You should also consider
the fact that they should be easy to move to allow
for cleaning and ventilation.
Exterior-mounted storm windows must have "weep
holes" at the bottom of the frame to allow any
moisture that collects between the primary window
and the storm window to drain out. Even though these
drainage holes subtract from energy savings, not
having them will eventually cause the primary window
frame to rot, and possibly make them impossible to
operate.
Caulking and
Weather-stripping
Most experts agree that caulking and
weather-stripping—two simple air sealing
techniques—will pay for themselves in energy savings
within one year. Applying these techniques will also
alleviate drafts and help your home feel warmer when
it's cold outside.
Before you use any air sealing technique in your
home, you need to do the following:
• Detect air leaks
• Assess your ventilation needs for indoor air
quality
Window Treatments and
Coverings
You can choose window treatments or coverings not
only for decoration but also for saving energy. Some
carefully selected window treatments can reduce heat
loss in the winter and heat gain in the summer. They
include the following:
Window treatments, however, aren't effective at
reducing air leakage or infiltration. You need to
caulk and weatherstrip around windows to reduce air
leakage.
