what is the R-value of the best window vs. the worst window? I"m getting ready to build a home and will prolly be going with Pella's 'Proline' version of windows. I know nothing about windows but the Pella's are in my price range. I keep reading/hearing about argon filled, low-e, double low-e, etc. Anyone care to explain.

Anyone know if the Pella's are good/bad??

Ron

 

Windows are usually not rated with r-values, because that would be deceptive. The r-value of a window changes depending on where the measurement is taken (frame, edge of glass, center of glass, etc). No window will be as energy efficient as a wall, so if someone says they have an r-20 window, they are full of hot air. If a vinyl window has a foam filled frame, the insulation itself may have a high rating, but it is such an insignificant part of the overall window that even the mention of it is over-rated. For this reason, many companies do not even fill their frames with insulation- it's not worth the trouble as far as energy efficiency is concerned.

The best rating to look at is the u-value and the solar heat gain coefficient. Both of these values are represented by a decimal, and the lower the number the better. Low-e/argon or triple-pane/krypton IGUs (insulating glass units)will give you the best u-values. Anything in the neighborhood of .30 or lower (.29, .25) would be considered excellent. Every window sold today is required to have a sticker disclosing these ratings so that consumers can compare apples to oranges and make some sense of it all.