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Energy Efficient Windows, Doors and Skylights & Climate Zones
New technologies allow a huge diversity of windows, doors and
skylights, with different energy performances.
These performances are measured mainly by the U-factor (the
rate of non-solar heat loss or gain)
and the
SHGC (a measure of the solar radiation admitted through a
window, door or skylight).
But the performances of a window, door or skylight shouldn't be
considered in abstract. A
low SHGC is a good indicator in warm or mild climates, but it
isn’t relevant in a very cold climate, where the solar radiation
admitted in a home is rarely negative.
In other words: energy efficient windows for UK, Massachusetts, Michigan or Minnesota
aren't the same of those
for Mexico, most of Australia, or Florida.
Efficient windows,
doors and skylights should present different U-factor and SHGC...
Conclusion:
When purchasing a window, a skylight or a door you should demand
products that
are qualified for your specific climate zone. The
Energy Star ratings (or the European BFRC and other ratings) are valid
and applied to specific climate zones...
Climate & glasses, frames and sashes
In cold and moderate climates, the most energy efficient
windows, skylights and glazed doors use
low-E coating
glasses, to reduce heat losses through the window.
In hot climates, the most
energy efficient windows, skylights and doors use solar control glass, also called
Low E2. This type of glass is the best to limit solar heat
gains (it blocks the infrared and some ultraviolet rays, more
than tinted window coating), besides being a good insulator and
transmitter of visible light...
The frames and the
sashes of windows, glazed doors and skylights should be made
of vinyl, fiberglass or wood. Aluminum fenestration should only
be used
with insulating
thermal breaks.
See for more details:
Glasses and windows, doors and
skylights
Frames and sashes
Climate zones for Windows,
Doors & Skylights
Broadly we can consider three big climate types
when equating the efficiency of windows, glazed doors and
skylights:
- the colder climates (alpine or cool temperate) where energy is
mostly used to heat the home. In this climate zones windows,
doors and skylights
should be selected to keep heat inside them.
- the warmer
climates (or tropical, subtropical and hot arid) where energy is
mostly used to cool the house. In these climate zones windows,
doors and skilights
should be selected to keep heat outside.
- the temperate
mixed climates where windows, skylights and doors should be selected and designed
for heating in winter and cooling in summer.
USA climate zones:
In the United States of America there are four Climate Zones for
Energy Star qualified windows, doors, and
skylights:
Northern: colder climates, demanding mostly heating windows
North/Central: temperate mixed climates
South/Central:
temperate mixed climates
Southern: warmer climates, demanding mostly
cooling windows

Source: www.energystar.gov
See also:
Detailed State US table with climate zones for windows, doors
and skylights
The U-factor
values and the SHGC in the
American Climate Zones
Energy Star Windows and doors:
Northern climate: U-factor: <0,35; SHGC: any
North-Central climate: U-factor: <0,40; SHGC: <0,55
South-Central climate: U-factor: <0,40; SHGC: <0,40
Northern climate: U-factor: <0,65; SHGC: <0,40
Energy Star Skylights:
Northern climate: U-factor: <0,60; SHGC: any
North-Central climate: U-factor: <0,60; SHGC: <0,40
South-Central climate: U-factor: <0,60; SHGC: <0,40
Northern climate: U-factor: <0,75; SHGC: <0,40
AUSTRALIA Climate Zones

In Australia the predominant climate is equivalent to the
American Southern, with the exception of Tasmania and the
southeast corner or mainland (cold climates) and the temperate
southern coastline and much of NSW.
Australian Window Energy Rating Scheme (WERS) rate windows for
the three big Australian climates:
rated
windows get from 0 to 5 stars for both cooling (summer) and
heating (winter).
Image Source:
www.greenhouse.gov.au
CANADA Climate Zones
Canada has been divided into four climate zones
when choosing windows, doors and skylights energy performance. The scheme
is very analogous to the USA system.

Image Source: Office of
Energy Efficiency Canada
US
TABLE WITH CLIMATE ZONES FOR WINDOWS, DOORS AND SKYLIGHTS
|
TYPE OF WINDOWS, DOORS
AND SKYLIGHTS |
|
State |
Climate Zone Window |
|
Alabama |
South/Central or
Southern |
|
Alaska |
Northern |
|
Arizona |
Northern or South/Central |
|
Arkansas |
South/Central |
|
California |
South/Central |
|
Colorado |
Northern or North/Central |
|
Connecticut |
Northern |
|
District of Columbia |
North/Central |
|
Delaware |
North/Central |
|
Florida |
Southern |
|
Georgia |
South/Central or Southern |
|
Hawaii |
Southern |
|
Iowa |
Northern |
|
Idaho |
Northern |
|
Illinois |
Northern or North/Central |
|
Indiana |
Northern or North/Central |
|
Kansas |
Northern or North/Central |
|
Louisiana |
Southern or South/Central |
|
Kentucky |
North/Central |
|
Maryland |
Northern or North/Central |
|
Massachusetts |
Northern |
|
Maine |
Northern |
|
Michigan |
Northern |
|
Minnesota |
Northern |
|
Mississipi |
South/Central or Southern |
|
Missouri |
Northern or North/Central |
|
Montana |
Northern |
|
Nevada |
Northern or South/Central |
|
New Jersey |
Northern or North/Central |
|
New Mexico |
North/Central or Northern |
|
North Carolina |
North/Central or South/Central |
|
North Dakota |
Northern |
|
Nebraska |
Northern |
|
New Hampshire |
Northern |
|
New York |
Northern |
|
Ohio |
Northern or North Central |
|
Oklahoma |
South/Central |
|
Oregon |
Northern |
|
Pennsylvania |
Northern |
|
Rhode Island |
Northern |
|
South Carolina |
South/Central |
|
South Dakota |
Northern |
|
Tennessee |
North/Central or South/Central |
|
Texas |
South Central or Southern |
|
Utah |
Northern or South/Central |
|
Vermont |
Northern |
|
Virginia |
North/Central |
|
Washington |
Northern |
|
West Virginia |
Northern or North/Central |
|
Wisconsin |
Northern |
|
Wyoming |
Northern |
For more information:
Windows, doors and skylights basics
Windows, skylights, doors & rating
Frames and sashes
Advanced Doors
Skylights
Weatherstripping
Caulking
Rebates and Tax Credits
Back to top Energy Efficient Windows and Climate Zones
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