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Replacement Window Ratings
Energy efficient windows can help homeowners cut down on their energy costs and help create a more comfortable home environment. These are the five performance numbers and terms that consumers should look at when comparing different windows to one another.
U-Factor
U factor measures how much heat loss occurs and is sometimes referred to as U-value. U-factor is a number that ranges anywhere from 0.15 to 1.20 - the lower the number, the more energy efficient the window. A U-factor above .35 is considered poor, between .34 and .27 is considered decent, and a U-factor at or below .26 is considered very good. The Marvin Infinity has a U-factor of .30, an okay rating even though the window is considered a very good one. Check out more Marvin window prices.
Air Infiltration
Air infiltration measures how much air passes through a window unit and is often abbreviated AI. Air infiltration is a number that ranges anywhere from 0 to .30. An AI above .15 is considered poor, between .14 and .07 is considered decent, and an AI at or below .06 is considered very good. The 9500 window from American Craftsman has an air infiltration of .12 - not horrible, but not the best out there to be sure.
Solar Heat Gain Coefficient
Solar heat gain coefficient measures how much heat passes through a window and is often abbreviated SHGC. Solar heat gain coefficient is a number that ranges anywhere from 0 to 1. SHGC will vary based on location and overall temperature and environment. For hot location, consumers should opt for a lower SHGC, while colder climates usually require a higher SHGC to allow more passive heat through the glass.
Design Pressure
Design pressure measures the amount of pressure (pressure load) that a window can withstand. (It is often abbreviated DP.) Design pressure is a number that ranges anywhere from 0 to 100. Most residential home windows will have a DP between 20 to 40, while hurricane or impact windows will have a DP rating between 45 and 100. The higher the DP rating, the more wind pressure a window can withstand. Most well made hurricane windows with a DP45 rating should hold up well under extreme weather. The 2300 Series from PGT has a DP50 rating and is considered a very solid hurricane window. Explore PGT impact windows pricing.
Visible Transferrance
Visible transferrance measures the amount of light that passes through a window and is often abbreviated VT. Visible transferrance is a number that ranges anywhere from 0 to 1. The 2900 Series from Silverline has a .58 VT, not a great rating. More Silverline windows prices.