What Does the NFRC Label Measure?

NFRC ratings describe specific areas of energy performance. Depending on the product and label, the information may include U-factor, solar heat gain coefficient, visible transmittance, air leakage and condensation resistance.

These values are not interchangeable. A window can perform strongly in one category without being the ideal choice in every other category. Contractors should connect the ratings to the orientation, climate, room use and homeowner’s priorities.

U-Factor: Heat Transfer Through the Entire Window

U-factor measures how readily heat passes through the window assembly. It evaluates more than the center of the glass. The certified value represents the performance of the complete product, including the glass, spacer, sash and frame.

A lower U-factor indicates less heat transfer. In a heating-dominated climate, this can help reduce heat loss through the window during cold weather. It may also help the interior glass surface remain warmer, although surface temperature depends on indoor and outdoor conditions.

What contractors should not promise

A lower U-factor does not translate into a guaranteed percentage reduction in the homeowner’s utility bill. Actual energy use also depends on the wall, attic, mechanical equipment, air sealing, thermostat settings, window area, orientation and occupant behavior.

Solar Heat Gain Coefficient: Managing Heat From the Sun

Solar heat gain coefficient, abbreviated SHGC, measures how much solar heat enters through the window. The value falls between zero and one. A lower number means the product admits less solar heat.

Lower is not automatically better in every opening. Reducing solar heat can be valuable for windows exposed to strong summer sun. A higher SHGC can sometimes provide useful winter solar gain, but it can also contribute to overheating and glare.

Orientation matters. West-facing glass may receive intense late-day summer sun, while north-facing glass usually has different solar-control needs. Overhangs, trees, neighboring buildings, porches and interior shades also affect the real-world result.

Better sales question

Instead of asking whether the customer wants the “best glass,” ask which rooms become uncomfortable in the afternoon, where fading is a concern and whether the home has substantial unshaded glass.

Visible Transmittance: How Much Daylight Gets Through?

Visible transmittance, or VT, describes how much visible light passes through the complete window. A higher value generally means more natural light.

Low-E coatings, tint, additional panes, screens and grids can affect the amount of visible light. A glass package with excellent thermal or solar-control performance may transmit less daylight than a basic clear-glass unit.

That tradeoff is not necessarily a defect. A homeowner may gladly accept somewhat less daylight to reduce glare or solar heat. The contractor’s job is to explain the balance rather than declaring that the highest VT is always best.

Air Leakage: Product Testing Versus Installation Leakage

NFRC describes air leakage as the amount of air entering through a product. Lower measured leakage indicates tighter product performance under the applicable test conditions.

However, the product rating does not measure air leaking between the window frame and the rough opening. That perimeter is created at the jobsite. Incomplete air sealing, poorly connected flashing or an uneven opening can undermine an otherwise well-performing window.

Homeowners may also mistake cold interior glass or natural convection for outdoor air leakage. Contractors should investigate the source of a “draft” before promising that a particular glass package will eliminate it.

Condensation Resistance Is Not a No-Condensation Guarantee

When provided, condensation resistance is a relative rating. A higher number indicates that the product is better able to resist condensation under the standardized rating conditions.

No practical window can guarantee that interior condensation will never appear. Condensation occurs when a surface falls below the dew point of the surrounding air. Extremely cold weather, high indoor humidity, closed coverings and restricted airflow can create condensation even on a high-performance window.

Condensation between the panes is a different issue. It may indicate a loss of the insulating glass seal and should be evaluated under the applicable product warranty.

How Gentek 1900 Series Glass Features Affect Performance

Gentek identifies insulated glass packages with Low-E glass, the Super Spacer structural foam spacer system and optional insulating argon gas for 1900 Series windows. These components can work together to improve thermal performance, but each feature serves a different purpose.

Feature names are useful, but the certified whole-product NFRC values are the stronger comparison tool. Two products advertised with Low-E glass and argon can still have different certified ratings.

NFRC Certification and ENERGY STAR Are Not the Same Thing

NFRC provides standardized third-party energy-performance ratings. ENERGY STAR uses qualifying NFRC-certified ratings to determine whether a product configuration meets its program requirements.

Therefore, an NFRC-certified product is not automatically ENERGY STAR certified. The exact window must satisfy the current ENERGY STAR criteria applicable to its climate zone.

Contractors should also avoid using an outdated thermal chart to establish current eligibility. ENERGY STAR criteria and product configurations can change. Verify the current NFRC label, ENERGY STAR certification information and regional requirements before making a representation to the customer.

NFRC Label Versus the AAMA Gold Label

These labels serve different purposes and should not be presented as substitutes for one another.

The NFRC label reports certified energy-performance values. The AAMA Gold Label Certification Program addresses qualifying product performance under standards that include air, water, structural and applicable durability requirements.

FGIA states that the AAMA Gold Label indicates that a product sample was independently tested and that ongoing manufacturing inspections help confirm continued compliance. The Gold Label does not replace the NFRC label when thermal ratings are needed.

Installation Can Protect—or Undermine—Energy Performance

The NFRC rating belongs to the manufactured window, not the entire installed wall opening. Field performance still depends on proper sizing, shimming, fastening, flashing, drainage and perimeter air sealing.

The FGIA InstallationMasters program provides professional education and certification for window and exterior glass-door installation. That training can support better installation practices, but contractors must still follow current Gentek instructions, project details and local code requirements.

A premium glass package cannot correct missing perimeter insulation, an incomplete interior air seal or water-management defects around the opening.

Sales Tips for Presenting NFRC Ratings

1. 1. Start with the homeowner’s problem. Ask about cold glass, summer overheating, glare, fading, condensation and comfort before recommending a glass package.
2. 2. Compare complete window ratings. Do not compare one manufacturer’s center-of-glass value with another product’s whole-window NFRC rating.
3. 3. Explain tradeoffs. Lower SHGC may reduce solar heat while also changing visible light. A product decision should reflect the actual opening.
4. 4. Offer documented choices. Present good, better and best configurations with their corresponding NFRC values instead of relying on feature names.
5. 5. Avoid savings guarantees. Window ratings permit comparison, but they do not control every variable in the home.
6. 6. Keep the label. Photograph or retain the NFRC label before removal when project records, inspections, rebates or tax documentation may require it.

Popular Homeowner Questions

Contractor Preorder Checklist

• Identify every required window style and size.
• Ask about room orientation and existing comfort problems.
• Select the proposed Gentek insulated glass package.
• Confirm the whole-product U-factor and SHGC.
• Review visible transmittance when daylight or tint matters.
• Verify current ENERGY STAR eligibility when it is promised.
• Do not use an old thermal chart as final proof.
• Confirm code, rebate and tax-documentation requirements separately.
• Retain NFRC labels and final order documentation.
• Use current installation instructions for the exact product.

Get Help Comparing Gentek 1900 Series Glass Packages

Suburban Wholesale & Supply helps contractors, builders and remodelers compare Gentek window configurations for projects throughout the Quad Cities. Bring the opening sizes, window styles, orientation and performance requirements so the team can help organize a more accurate quotation.

Glass packages, NFRC ratings, ENERGY STAR eligibility and product availability vary by style, size and configuration. Confirm current documentation for the exact ordered window before presenting performance values to a customer.