Master Frame: The main structural component that holds together the sashes

Sash Frame: The frame that holds the glass unit

Insulated Glass Unit (IGU): IGU’s are constructed from glass that ranges in thickness ranging between 3mm to 10mm. The two panes of glass are then sealed together with a spacer that provides insulation to the unit and gives it the appropriate thickness for the sash that it is to be inserted into. The IGU is then sealed with an adhesive sealant to keep moisture out of the unit.

Double Pane: An IGU with two panes of glass (see diagram A)

Triple Pane: An IGU with three panes of glass (see diagram B)

Low-E: Glass that has low emissivity because of a thin film or metallic coating that reduces heat transfer, it allows short wave solar energy into a building, but prevents long wave energy produced by heating systems and lighting from escaping outside. The coating during the summer the radiant heat is reflected preventing it from entering the building and during the winter it reflects the heat from the building back into the building.

Argon Gas: A safe odorless, colorless, non-toxic, non-flammable, inert gas that is inserted into in between IGU to reduce heat transfer

Krypton Gas: See Argon: The difference is that Krypton has better insulating values. Krypton is more effective when there is a smaller gap between the window panes (less than 3/8th of an inch). Krypton is also much more expansive than Argon increasing the cost of the windows.

Tempered Glass: Glass that is manufactured to be stronger, when it breaks it shatters into small piece. The glass is heated to just below the melting level, thus the silica molecules inside of the piece are bonded tightly together making the glass two times stronger than annealed glass.

R-Value: Resistance to thermal (Heat) flow, the higher the value the greater the insulation. R-value typically, not always, is derived from center of the glass only.

U-Value: Rate of heat flow through the entire window barrier, either from outside in or inside out. The lower the value the better the insulation. U-value typically, not always, is derived from all components including frame and glass.

Muntin/Grille/Grid: Aesthetic bar that separates a larger pane of glass into smaller members.

Head: The main horizontal member at the top of windows and doors

Window Sill: The main horizontal member at the bottom of a window or door

Egress: The minimum clear opening of a window required by building code for escape purposes. Presently that is 5.7 square feet.

Jamb: The vertical sides of a door or window. Windows are generally installed between jambs. It is not a component of the window itself.