Energy Efficiency FAQ’s

 So why is it important to know everything you can about the energy efficiency of your windows?

Coldness and heat can come through any poorly designed window.

How do I know the manufacture’s efficiency ratings are good?

Manufactures often use the non-profit organization- National Fenestration Rating Council (NFRC) to test their windows for energy efficiency performance.  When you see this sticker on a window, you can be assured that the window will perform the way the manufacture says it will perform, at least on the day it was manufactured.
Always look for whether or not the ratings are derived from ‘Full frame’ window value versus ‘Center-of-Glass’ (COG) value: Poorly insulated window frames can transfer unwanted heat or cold into your home. That’s why it is important to know the insulating capabilities of the entire window, not just the center of the glass. Full frame R-value or U-factor will tell you how good your entire window is at insulating.  Center of Glass measurements only tell you how well a small area of the glass performs and not the entire window including the frame.

Does the installation method affect the energy performance of a replacement window?

Heat can escape through the tiniest of openings.  Installers must properly seal the space between the new window frame and the home’s existing window frame.  This is the most important area to concentrate on to ensure the energy efficiency performance of the enter opening, not just what you can see through.  Make sure you ask how this space will be dealt with in full detail when getting an estimate for installation.  You want to make sure that no air, wind, moisture, water, or coldness can find it’s way in to your home after the window has been placed in to the opening.


U-factor measures how well heat is transferred by a window and can affect heating and air conditioning costs; the lower the U-factor, the better the insulating properties.


R-value is the standard measure of heat loss through a partition, such as a wall, window, or door; the higher the R-value, the better its insulating properties.  Washburn Windows uses Full Frame Window Values to measure it’s R-Value- meaning from the edge of frame to edge of frame, not just the glass portion of the window.

Solar Heat Gain Coefficient (SHGC)

Solar Heat Gain Coefficient measures the percent of solar heat that actually enters a building through a window. The smaller the number, the better the window is at preventing too much warmth from coming in.

Visible Light Transmission (VT)

Visible Light Transmission neasures how much light comes through the glass; the lower the number the less visible light is transmitted

UV Blockage

UV Blockage measures the percentage of damaging solar radiation that is blocked and not allowed to enter your home. The higher the percentage, the less fading and damaging to your furnishings and carpet.
Washburn Windows, Your local Window Depot USA dealer uses only the best of the best window and door products with life time warranties.  To meet Energy Star criteria, windows must be certified by the National Fenestration Rating Council (NFRC), an independent organization that tests and certifies windows for their energy performance.  This provides consumers with a way to compare one window’s energy performance to another in a non-bias way.   All of our windows have been tested and certified and have some of the highest energy ratings in the vinyl window replacement industry.  You can easily search the window manufacture’s NFRC ratings so that you can compare “apples to apples”.  Everyone tries telling you that “our window will save you the most energy” and at the same time, are often not even certified with NFRC.  The fact is that most of the time there are other more energy efficient NFRC certified windows available at a lower cost.  The NFRC label certifies that the window product actually performs the way it’s advertised to perform.   This is why Washburn Windows does very well in the vinyl window business.  When you are getting quotes from various window dealers, ask the dealer for the NFRC window’s energy performance ratings.