Understanding NFRC window performance ratings

We know it can be confusing to compare window quality and make an intelligent decision on total value. At Wonder Windows, Showers and Baths we help consumers make sense of all the numbers; what they mean and really what is important to consider when making this investment decision for your home.

By law the NFRC label is affixed to all types of windows, skylights, and entry or patio doors. Performance ratings are broken down to 4 categories that are important to consider:

In addition you should also understand the rating for Air Leakage (AL). This important factor is about the frame and how air tight a window is to the frame so that it reduces the amount of heat that escapes (or how much cool air can be lost) through a closed window.

A.  U-Factor (At Wonder Windows, Showers and Baths we think this is very important and so should you!) 
This is a measurement the rate of heat transfer. How heat escapes from your home to the outside. Very important to Homeowners in the Northeast. Window U-Factor values can range from 0.25 to 1.25. Just remember The lower the U-factor, the better the window keeps heat in your home. The more heat kept in your home the lower your heating bill.

For Energy Star qualification in the Northeast a window must have:
a minimum U-Factor of ≤ 0.27
Obviously the lower the U-Factor the greater the cost of a window. LOWER IS BETTER

For our OKNA Windows 

B. Solar Heat Gain Coefficient (SHGC) is a measurement of how well a windows stops heat from getting IN your home or how well the window blocks heat caused by sunlight. The SHGC measurement is on a scale of 0 to 1; typical ratings range from 0.25 to 0.80. The lower the SHGC, the less heat from the sun the window transmits to the inside of your home. The less heat allowed to enter your home from sunlight the lower your cooling cost.

For Energy Star qualification in the Northeast a window must have:
a minimum SHGC of "any"
While the Energy Star requirements are not calling for minimum rating the lower the SHGC the greater the cost of a window and better the energy savings. LOWER IS BETTER

C.  Visible Transmittance (VT) 
VT measures the amount of light let through a window. VT is measured on a scale of 0 to 1; values commonly vary from 0.20 to 0.80. The higher the VT number, the more light you see. HIGHER IS BETTER

D.  Condensation Resistance This is also something important to homeowners in the Northeast when you think about ice building up on the window in the winter. CR 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 of moisture the window allows.
Obviously the higher the condensation resistance of a window the better and more it may cost. HIGHER IS BETTER

Air Leakage (AL) "OK this is a big deal in the Northeast"
AL measures the rate air passes through the window. This has to do with the frame and how well the window fits in the frame to stop air moving in or out of your home. AL is measured in cubic feet of air moving through 1 sq.ft. of window area / minute. The lower the AL value, the less air escapes or enters your home.

Building codes (Industry standards) require an AL of 0.3 cf·m/ft².
Obviously the better the frame and fit the more a window may cost. LOWER IS BETTER

AL) Ratings for our OKNA Windows are Simply Amazing

At Wonder Windows, Showers and Baths we believe an educated consumer is our best customer. We carry a full line of high performance replacement windows and doors with both savings on energy usage and more importantly your wallet.

For a FREE Estimate

call 585-547-5520