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A properly sealed, well-insulated addition will increase the comfort
of your home while costing less in the long run. Extensive information
is available on the building
envelope—windows, insulation, foundation, structure, and
roofing—to help you plan your addition.
Insulating your home has a general
discussion of recommended insulation levels and types of insulation.
See also sealing air and moisture leaks,
which discusses vapor and moisture barriers.
An important option to consider for new additions is to use structural
insulated panels (SIPs, also called foam-core panels), which are
thick slabs of foam insulation sandwiched between two layers of
a structural material such as plywood. They can be used for both
walls and ceilings. Although SIPs cost more than traditional building
materials, they require less labor to install, so the total cost
is roughly the same as stud-framed walls. For more information about
SIPs, see the EREC Reference Brief, Foam-Core
Panels.
Building an addition also gives you the opportunity to size and
place your windows to provide the best light and ventilation. Windows
can also be located to provide solar heating in cold climates or
avoid solar heating in hot climates. In cold climates, where solar
heating is desirable, you should also consider ways to add thermal
mass, such as tiles, masonry, or even water-filled walls to the
floors and walls near south-facing windows. See using
solar in your home.
A common approach is to add on a sunspace. Sunspaces can provide
useful solar heat to your home, but must be vented in the summer
to prevent overheating. For more about sunspaces, see the EREC fact
sheet, Sunspace Basics (PDF 173 KB). Download Adobe Reader.
Windows also offer an opportunity to add daylighting to your home.
If practical, clerestory windows are an effective way to add both
light and ventilation to a home. In a clerestory design, one part
of the roof is positioned higher than the other, with vertical windows
bridging the gap between the two.
Another obvious approach is to add skylights, but they often cause
overheating in the summer and heat loss in the winter. Triangular
"roof monitors," with vertical glazing, are a more energy-efficient
approach. If you are considering installing skylights, learn more
about them in a brief
from the Energy Efficiency and Renewable Energy Clearinghouse.
In climates where natural ventilation makes sense, windows need
to be located on both the windward and leeward sides of the house.
Roughly equivalent-sized openings on both sides of the house will
maximize the airflow through the house. The windows should be offset
so that the air will circulate through the house rather than blowing
directly through it.
Windows can now be designed for a number of purposes. Some windows
are designed to let the sun's heat in while insulating against the
cold, and are ideal for south-facing windows in cold climates. Others
are designed to reject the sun's heat while providing insulation,
and are ideal for all windows in hot climates and east- and west-facing
windows in moderate climates. See Buying
for Energy Efficiency: Windows for information about which windows
you should buy for your location.
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