Understanding Window Efficiency Labels and How To Lower Your Utility Bills With An Energy Efficiency Evaluation…

Scheduling an energy efficiency evaluation of your home and learning more about how much you can save is an eye opening experience. New windows are a major way to keep the work done by your HVAC System INSIDE your home or office! With the current emphasis on energy efficient windows, the National Fenestration Rating Council has designed an energy-performance label to guide contractors and homeowners in their search for the perfect window. Since the climates in different parts of the United States vary widely, checking the label before ordering the window can make a big difference in how much the window can help your client keep energy costs to a minimum. But what do all those numbers and codes on the label mean? Once you know what to look for, you’ll be able to find exactly the right windows. Here’s a quick tour:

Where Is The Label Found?

NFRC Certified labels are found in the upper left corner of the window. These labels indicate that the National Fenestration Ratings Council has licensed the window’s manufacturer and certified the window’s performance in accordance with NFRC’s standards. Labeling on the upper right corner identifies the window’s manufacturer, model, style, and the materials used in its construction.

The U-Value

NFRC Label definition of U-value is the measure of heat transmission through a building part (such as a wall or window) or a given thickness of a material (such as insulation) with lower numbers indicating better insulating properties. The U-factor is the rate of heat loss from a building as indicated in terms of the U-factor (U-value). U-Factor ratings for windows generally fall between 0.20 and 1.20. The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value. (The window’s insulating value is indicated by the R-value, which is the inverse of the U-value.)

The Solar Heat Gain Coefficient

The NFRC Label defines SHGC- the fraction of incident 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. The solar heat gain coefficient (SHGC) indicates how well a product blocks heat from the sun. The SHGC is the fraction of incident solar radiation admitted through a window and absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. Again, the lower the number, the better a s low SHGC means the window transmits less solar heat.

Visible Transmittance

The NFRC Label defines the VT- Visible Transmittance is influenced by the glazing type, the number of panes, and any glass coatings. Visible transmittance of glazing ranges from above 90% for uncoated water-white clear glass to less than 10% for highly reflective coatings on tinted glass. A typical double-pane IGU had a VT of around 78%. 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.

Air Leakage

The NFRC Label defines the AL as the heat loss and gain which occur by infiltration through cracks in the window assembly. It is indicated by an air leakage rating (AL) expressed as the equivalent cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the window assembly. An AL rating is required, this rating must be 0.30 or less and can be displayed on the NFRC’s  label. The lower the AL, the less air will pass through cracks in the window assembly.

Condensation Level

NFRC Label defines the CR as the Condensation Level that measures the ability of a product to resist the formation of condensation on the interior surface of the product. The higher the CR rating, the better that product is at resisting condensation formation. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation formation. CR is expressed as a number between 0 and 100.

The Manufacturer’s Label

Look for product certification labeling such as the AAMA (American Architectural Manufacturers Association) permanent label . These labels provide important information about the product and contain the product’s brand name or manufacturer’s code. Permanent labels are commonly affixed somewhere along the frame of a product. Manufacturer identification is the first and most essential step when ordering service parts or beginning service work on windows and patio doors. Proper identification is also important because warranty coverage terms vary with manufacturer, product, and date.  It should list the basic product features:  frame materials (wood, aluminum, vinyl, steel or fiberglass), number of panes (single, double or triple), type of gas filling the gap in multi pane window (usually argon or krypton), the glazing-style, and the Low-E (a glass treatment that reduces harmful UV rays that can fade your furniture and carpets.)

The Energy Star Label

ENERGY STAR is the trusted, government-backed symbol for energy efficiency helping us all save money and protect the environment through energy-efficient products and practices. The ENERGY STAR label was established to reduce greenhouse gas emissions and other pollutants caused by the inefficient use of energy. If a window meets certain performance guidelines for your geographical area, its label may also feature the Environmental Protection Agency’s Energy Star logo. This lets you see at a glance which windows have the most energy efficient properties. To see the Energy Star criteria for your area, refer to Energy Star’s climate map for windows, skylights, and doors.

Purchasing Your Windows

Once you know what each of the numbers on the labels means, you’ll be able to make informed purchase decisions and get the most bang for your buck. Drafty, single-pane windows can be brutal on a home’s energy efficiency. In many older homes, window replacement is one of the most effective potential investments in long-term energy savings. But choosing from among dozens of window brands and models can feel overwhelming, especially if you don’t understand all the information on the window labels.

If you are looking to make your home more comfortable while lowering your utility bills, give us a call to schedule an energy efficiency evaluation of your home and learn more about how much you can save.

Contact us (859-918-5400) for a Free Consultation!


About Phoenix Comfort Systems

Phoenix Comfort provides a full range of air conditioning and heating repair, installation, and maintenance services for residential and commercial customers. We keep your air conditioning and heating systems in their best condition and ready to go when you need them most, following the industry’s “best practice” methods and standards. Phoenix Comfort carries a full line of quiet, energy-efficient air conditioning and heating equipment.
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