|Looking for Energy Efficient Windows?
It's SIMPLE... well, with the new catch
The ENERGY STAR label was designed to make choosing high performance, energy
efficient windows simple. Homeowners no longer need to be concerned with
companies claiming their windows have this R-value, that air-infiltration or boasting
about other confusing or misleading data. They only have to find a window with the
easy to identify ENERGY STAR label. A window with the ENERGY STAR label must be
tested by an independent laboratory and certified by the National Fenestration Rating
Council (NFRC). A program of the U.S. Department of Energy and Environmental
Protection Agency, ENERGY STAR was designed to
set apart (approximately) the top 30% of energy
products based on their performance.
Current 2010 ENERGY STAR Performance Criteria
In response to changing technologies, as well as state and international codes,
since January 2010, windows are now required to meet new, more difficult to
achieve U and SHGC values to be labeled as ENERGY STAR. For most of Maryland
and Washington DC, windows are required to have a U-Value <= 0.32 and a
SHGC <= 0.40. NOTE: While many were expecting the new 2010 ENERGY STAR
criteria to be equivalent to the tax credit criteria, buyer beware, it is not.
WeatherMaster is a proud partner with the U.S. Department of Energy and EPA in
the ENERGY STAR program. We encourage homeowners learn more about energy
efficient products, and consider their long term payback when making purchase
decisions. Often times, the most energy efficient choice is also the most economical.
Additional information is available at the ENERGY STAR website.
The NFRC Certification Label
An opening in a building's outer shell (or "envelope") is called fenestration, a term
that includes windows, skylights and doors. Since 1993, new windows began carrying
energy efficiency labels from an organization called NFRC — the National
Fenestration Rating Council.
NFRC is a non-profit, public and private organization created by the window, door and skylight industry. Its membership includes manufacturers, suppliers, builders, architects and designers, building code officials, utilities and government agencies.
NFRC's primary goal is to provide standardized accurate information to consumers, making it possible to measure and compare the energy performance of window, door or skylight products.
The NFRC label describes the type of window, and rates it for these factors:
U-factor is a measure of how well heat is transferred by the entire window — the frame, sash and glass — either into or out of the building. The lower the U-factor number, the better the window will keep heat inside a home on a cold day. Typical U-factors for windows range from 0.50 (poor) to 0.18 (excellent).
Solar heat gain coefficient (SHGC) is a measure of a window's ability to transmit
warmth caused by sunlight. A lower number means less heat is getting through,
resulting in reduced air conditioning costs during the hot season. Typical SHGCs for windows range from 0.61 (poor) to 0.18 (excellent).
Visible light transmittance measures how much light gets through the window. A
window with a high number will allow more natural daylight into your home.
An NFRC label merely presents objective information. It does not distinguish
between a "good" window and a "bad" window, nor does it set minimum
performance standards or mandate performance levels.
When comparing U and SHGC values, make sure they are from the NFRC product
sticker, not "GLASS" or "CENTER OF GLASS" ratings. NFRC values are based on the
"WHOLE WINDOW" performance which more closely represent the energy efficiency
of the entire window. To compare other values is to compare apples with oranges.
Center of glass values are always lower (better) than whole window values.
Various information courtesy of the Department of Energy and ENERGY STAR www.energystar.gov,
and the California Energy Commission www.consumereneravcenter.org