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Structural & Testing

The energy performance of all qualified ENERGY STAR vinyl windows, doors, and skylights must be independently tested and certified according to test procedures established by the National Fenestration Rating Council (NFRC) .

NFRC is a third-party non-profit organization that sponsors certified rating and labeling to help consumers compare the performance of windows, doors, and skylights. NFRC does not distinguish between “good” and “bad” windows, set minimum performance standards, or mandate performance levels. This is where ENERGY STAR comes in. ENERGY STAR enables consumers to easily identify NFRC-certified products with superior energy performance.

The NFRC label can be found on all ENERGY STAR qualified windows, doors, and skylights and provides performance ratings in five categories.

NFRC Performance Ratings

  • U-Factor measures the rate of heat transfer and tells you how well the window insulates. U-factor values generally range from 0.25 to 1.25 and are measured in Btu/h·ft²·°F. The lower the U-factor, the better the window insulates.
  • Solar Heat Gain Coefficient (SHGC) measures the fraction of solar energy transmitted and tells you how well the product blocks heat caused by sunlight. SHGC is measured on a scale of 0 to 1; values typically range from 0.25 to 0.80. The lower the SHGC, the less solar heat the window transmits.
  • Visible Transmittance (VT) measures the amount of light the window lets through. VT is measured on a scale of 0 to 1; values generally range from 0.20 to 0.80. The higher the VT, the more light you see.
  • Air Leakage (AL) measures the rate at which air passes through joints in the window. AL is measured in cubic feet of air passing through one square foot of window area per minute. The lower the AL value, the less air leakage. Most industry standards and building codes require an AL of 0.3 cf·m/ft².
  • Condensation Resistance measures how well the window resists water build-up. Condensation Resistance is scored on a scale from 0 to 100. The higher the condensation resistance factor, the less build-up the window allows.

For more information on NFRC performance ratings and label, visit NFRC’s Web site. ENERGY STAR qualification is based on U-factor and SHGC ratings only.

Many Krestmark windows meet or exceed the strict Energy Star criteria when ordered with options such as Argon gas enhancement.

Note: All picture windows, shapes and one-frame glass larger than 30 square feet will come with Tempered Glass as standard for safety reasons. All additional charges for Tempered Glass will automatically be applied.

Product lines and their components, building codes, installation techniques and third party certifications are constantly evolving. For the most current information, check our website frequently at www.www.krestmark.com.

Krestmark Industries, LP. reserves the right to improve, change or discontinue product lines and/or components without notice.

Krestmark Industries, Windows  Installation & Service, Dallas, TX