A measure of how well a product blocks heat from the sun. The lower the SHGC, the better a product is at blocking unwanted heat gain. SHGC is measured on a scale of 0 to 1; values typically range from 0.25 to 0.80.
A measure of how well a product prevents heat from escaping
a home or building. U-Factor values generally range
from 0.25 to 1.25. The lower the U-Factor, the better
a product is at keeping heat in.
Visible Transmittance (VT)
A measure of how much light comes through a product. The higher the VT, the higher the potential for daylighting. VT is expressed as a number between 0 and 1.
Air Leakage (AL)
A measure of how much outside air comes into a home or building through a product. AL rates typically fall in a range between 0.1 and 0.3. The lower the AL, the better a product
is at keeping air out. AL is an optional rating, and
manufacturers can choose not to include it on their labels.
Condensation Resistance (CR)
A measure of how well a product resists the formation of condensation. CR is expressed as a number between 1
and 100. The higher the number, the better a
product is able to resist condensation.
ENERGY STAR is a joint program of the U.S.
Environmental Protection Agency and the U.S.
Department of Energy helping us all save money
and protect the environment through energy efficient
products and practices including windows and doors.
2009-10 Stimulus Tax Credit
In order to qualify for up to $1500.00 off your income tax the window and door you install must meet the following criterira:
1. ENERGY STAR approved product
2. Must have a U-factor of .30 or less
3. Must have a SHGC of .30 or less
4. Must have low-E coating on glass
National Fenestration Rating Council (NFRC)
The National Fenestration Rating Council is a non-profit
organization that administers the only uniform, independent
rating and labeling system for the energy performance of
windows and doors, skylights and attachment products.
HOW TO MEASURE THE EFFCIENCY OF A WINDOW AND DOOR?
A window and door is measured to be efficient using the five overall criteria below. The two main characteristics are Solar Heat Gain and U-factor. These ratings are found on the fenestration label that should be attached to every window and door.
WHO MEASURES THE EFFCIENCY OF A WINDOW AND DOOR?
The main independent organization for certifying a window and door is the NFCR. Energy Star is also a rating system provided by the United States Department of Energy.