Low-e is an invisible coating applied to the glass surface of windows to reflect heat back to its source. In the summer when the suns rays are shining down more strongly, low-e reflects some of that heat back outside the home whereas clear glass allows the heat to enter the home and heat it up.

Low-e does not have any impact on how much air gets through the window creating drafts.

Argon is an inert non-toxic gas that is put into an insulated glass unit to help with the efficiency.

Single, double and triple pane refers to the amount of glass in a window. Original wood windows were made with just one piece of glass. Eventually they were replaced with double pane glass which is the most common type of glass today. Triple pane glass incorporates a third layer of glass which further enhances energy efficiency.

Similar to argon, krypton is an inert gas inserted between panes of glass. Krypton is usally used for triple pane windows instead of argon which is more common in double pane.

Typically new construction vinyl windows are used in installations for homes and buildings that are being built from scratch. Replacement windows are usually for situations where the building has already been built and has windows that are being replaced.

The only difference in the contruction of the window is the inclusion of a nailing flange around the outside frame of the window. New constructyion windows have nailing flanges, replacement windows do not.

A nailing flange allows a window to be installed from the exterior of the building whereas a replacement window is typically installed by screwing through the jamb. In order to use a nailing flange you must have access to the area around the window on the exterior of the building which is typically covered with siding on structures that are already built.

Fusion welded windows are much more energy efficient then mechancincally fastned.

Fusion welleded frames are literally melted into each othere so there are no gaps. Mechanically fastened are attached with screws. Over time as vinyl naturally expands and contracts mechanically fastned windows will degrade in energy efficiency.

Not all vinyl is the same. Certain vinyl windows use lower quality vinyl that will degrate over time.