PVC  Poly Vinyl Chloride: This is the plastic compound used to make Vinyl windows. Ultraviolet inhibitors are added to prevent yellowing and extend the life expectancy.

Grade : This number is the "design pressure".  It measures the structural integrity of the window. The higher the number the better the window is at resisting air & water infiltration in windy conditions.

U Value:  This is the insulating quality of the window. The lower the number the better. " Energy Star" rated  products must have a  U-Value of  .35 or lower (must be .30 for Tax Credit)

Low E Glass: A coating applied to standard (clear) glass which reflects radiant heat and increases energy efficiency. This coating generally makes a window "Energy Star " rated according to EPA guidelines.  Adds a slight tint to the window.

Argon Gas:  Argon gas replaces the air between the hermetically sealed panes of glass and reduces conductive heat loss through the glass pack. Used together with Low E glass to further improve the energy efficiency.

Double Strength Glass:  50% thicker than standard single strength glass. Better insulating and has better resistance to breakage.

Constant force balance and block & tackle balance: the latest in sash balance systems. Both offer superior life expectancy & smother operation than the older style spiral balance.