Understanding The Energy Star Ratings on Windows and Doors.

Energy Efficient Windows in Fairfax County, Virginia.
Energy Star Window, Door and Sunlight Ratings Can Be Confusing.  We’ll Make Sense Of It All.

Many homeowners are confused by the labeling and different energy ratings and claims made by manufacturers.  It’s one of the most confusing parts of trying to make the most energy efficient window choice.  This article will try and make some sense out of the Energy Star window ratings for windows, doors and skylights.

Did You Know…?  In order for a manufacturer to make any claims relating to energy efficiency of their product it must be independently tested and certified according to specific test procedures that are established by the NFRC (National Fenestration Rating Council).  The 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.

The NFRC however, does not distinguish between “good” or “bad” they do not set minimum performance standards nor do they mandate the performance levels.  This is where the Energey Star programs comes in.  With the Energy Star program consumers are able to quickly identify products that have superior energy performance and efficiency.

The NFRC energy rating label can be found on all Energy Star qualified window, door, and skylight products.  The Energy Star program for windows ranks windows based on 5 different performance categories.

  • U-Factor:  This measures the rate of heat transfer between the inside of your home to the outside 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.

Are you thinking about replacing your windows or doors with more energy efficient products?  Innovative Contracting is a full service home improvement contractor serving Fairfax County, Virginia.  We specialize in installing energy efficient windows, doors and skylights into local homes and businesses throughout the Fairfax County area.

Give us a call today or fill out one of our contact forms and we can provide you with a Free Estimate for your project and answer any of your questions related to Energy Star rated home improvement products and upgrades.