American Vinyl Windows

Replacement Windows Ratings

Replacement windows have 4 different factors for evaluating window performance. These criteria are used by the National Fenestration Rating Council or commonly known N.F.R.C.

The first factor of window ratings would be U value. This is a term used to score the conduction factor of the window. The most energy efficient windows have the lowest u values. Triple pane windows can have values approaching .15 which is fantastic. The inverse of the u value is the R value which is a more commonly used term for energy efficiency. This is known as the resistance factor and is widely used to rate windows, attic insulation and roofing. In the pervious example of the replacement windows u value of .15 would translate into an R value of over 9.

The next replacement window ratings would be solar heat gain coefficient. This will measure how well the replacement window can block heat from the sun. The lower the SHGC the better the window can block out the sun. Vinyl replacement windows can achieve very low numbers.

The third measurement of window performance would be air leakage or air infiltration. The lower the value the better the window performs. The windows typically perform between .1 and .3. The best windows are near a .1 level of air infiltration. These windows are commonly insulated vinyl replacement windows. They have filled the cavities and chambers of the vinyl windows with foam or polystyrene insulation. In addition the mechanic can put insulation around the jambs during installation for better window performance.

The final window rating is visible transmittance. These measures how much light comes through the product? The higher the number would indicate more light coming through the product.

Overall when researching windows look for a replacement window with the lowest values and you will achieve the best performance. These do vary by regions. Chicago replacement windows will obtain different ratings then other areas because of climate conditions. For example windows in Arizona need a windows to block out more light (VT) then replacement windows in Chicago where sun is not the culprit.