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How To Compare Window Energy Performance

The National Fenestration Rating Council (NFRC) energy performance label can help you determine how well a product will perform the functions of helping to keep your home cool in the summer and warm in the winter.

By using the information contained on the label, builders and consumers can reliably compare one product with another, and make informed decisions about windows and doors.

NFRC adopted a new energy performance label in 1998. It lists the manufacturer,
describes the product, provides a source for additional information, and
includes ratings for one or more energy performance characteristics.


U-Factor

U-factor measures how well a product prevents heat from escaping. The rate of
heat loss is indicated in terms of the U-factor (U-value) of a window assembly.
U-Factor ratings generally fall between 0.20 and 1.20. The insulating value is
indicated by the R-value which is the inverse of the U-value. The lower the
U-value, the greater a window's resistance to heat flow and the better its
insulating value.

Solar Heat Gain Coefficient

Solar Heat Gain Coefficient (SHGC) measures how well a window blocks heat caused
by sunlight. The SHGC is the amount of solar radiation admitted through a
window, both directly transmitted, and absorbed and subsequently released
inward. SHGC is expressed as a number between 0 and 1. The lower a window's
solar heat gain coefficient, the less solar heat it transmits.


Visible Transmittance

Visible Transmittance (VT) measures how much light comes through a product. The
visible transmittance is an optical property that indicates the amount of
visible light transmitted. VT is expressed as a number between 0 and 1. The
higher the VT, the more light is transmitted.


What Makes Windows Energy Efficient?

Windows today are more energy efficient for several reasons. The material that makes up today's windows has a lot to do with energy efficiency. For example, the majority of windows sold in the United State have a vinyl or wooden frame, dual paned glass, and special energy efficient coating called LowE.  Often an inert gas, such as argon is inserted between the double panes providing another energy barrier.

What is LowE2, And How Can This Technology Reduce Your Energy Bill?

Spectrally selective glazing is window glass that has been treated to allow the
visible spectrum of light to pass, but blocks ( reflects ) the other spectrums, infrared (IR) and ultraviolet (UV). This type of glazing can transmit a high proportion of the visible solar radiation (sunlight), but screen out up to 80% of the infrared radiation.

This type of glazing can transmit a high proportion of the visible solar
radiation (sunlight), but screen out up to 80% of the infrared radiation.

This results in a low transmission of radiant heat from the sun, and reduces the
need to operate the Air Conditioning, thereby saving on energy cost.

 

How LowE Keeps Homes Warmer In Winter

                 

LowE increases the window's ability to reflect infrared radiation, which
reduces energy loss from a warm room, which means that heat is reflected back
into your rooms when it's colder outside.

Windows with Low-E coatings may cost 10-15% more than traditional windows, but
their energy loss is reduced by 30-50%.




How LowE Keeps Homes Cooler In Summer

                     

It has been proven that windows with a high solar heat gain, can account for
more than 50% of air conditioning costs. LowE was engineered and designed to
allow daylight to come through the window, but filters out the solar heat, and harmful UV rays.  Those UV rays are what cause carpet to fade, so by minimizing the UV rays allowed in we reduce carpet fade.






Double-Paned Windows

To improve a window's energy efficiency the number of glass panes in the window
unit is doubled, because multiple layers of glass increase the window's ability
to resist heat flow.

Double-glazed, or insulated, windows are the standard for window technology
today. Basically, a double-glazed window contains two layers of glass sandwiched
together for greater energy efficiency.

Glass is highly conductive, which means single-pane windows let heat pour out of
a room. By trapping air between two panes of glass, the thermal resistance is
more than doubled-a simple enough solution that the majority of windows in the
U.S. are now manufactured with insulating glass.

Good quality, double-glazed windows are generally more expensive than
single-glazed windows because of the additional cost of manufacturing. The insulation value or energy savings they provide certainly makes them a wise choice for the energy conscious home owner.
 

The Value of Argon Gas

Super-insulating argon gas has several benefits, first it reduces energy ( heat ) transfer by placing it between the panes of glass.  Next,  it also helps to reduce the level of noise that passes through.

Which Home Improvement Project Should Have Priority?


Energy efficient windows should certainly be among the priorities since this will have an immediate impact on your energy bills. An additional benefit of energy efficient windows is they help to maintain a more stable ( comfortable )  temperature all year long and may be replacing windows which allowed a drafty condition to exist.
 

For the Your Window Replacement needs
Call 703-963-2687  or view our Online Presentation, then get pricing !
 

Copyright  2003 Best Buy Windows, Inc. All rights reserved.
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