Window installation services glossary

Short, plain-English definitions of the terms you'll meet when choosing a window installation service provider in Connecticut.

What are weep holes?: Weep holes are small drainage openings in the sill or frame of a window that permit water, condensation, and moisture to drain outward rather than accumulate inside the frame.
What is a casement window?: A casement window is a side-hinged sash that swings outward on a vertical pivot or hinge, operated by an interior crank or lever mechanism.
What is a composite window frame?: A composite window frame is made from a blend of wood fiber and synthetic resin designed to combine the look of wood with improved moisture resistance and durability.
What is a design pressure (DP) rating?: Design pressure rating is a standardized measure of a window's structural capacity to resist wind-driven forces and prevent water leakage under specified pressure conditions.
What is a double-hung window?: A double-hung window features two vertical sashes that slide up and down independently, with both operable to allow air flow from top or bottom.
What is a fiberglass window frame?: A window frame made from pultruded fiberglass composite, designed to resist warping, rot, and thermal movement while requiring minimal maintenance.
What is a nailing fin?: A nailing fin is a flanged perimeter on a new-construction window frame designed to be fastened directly to wall sheathing and integrated with house wrap and exterior flashing.
What is a tilt-latch sash?: A tilt-latch is the mechanical locking mechanism on a double-hung window sash that allows the sash to pivot inward on its hinges for interior cleaning access.
What is a U-factor?: U-factor is a measure of how much heat escapes through a window, with lower numbers indicating better insulation performance; the scale runs from 0.20 to 1.20, and it appears on the NFRC label.
What is a vinyl window frame?: A vinyl window frame is a hollow PVC (polyvinyl chloride) extrusion with welded corner joints that forms the structural perimeter of a window unit, requiring minimal maintenance compared to wood or aluminum.
What is a window balance?: A spring or block-and-tackle mechanism inside a double-hung window frame that counterweights the sash so it stays in place when raised without external support.
What is an awning window?: An awning window is hinged at the top and swings outward from the bottom, allowing ventilation while shedding rain.
What is an egress window?: An egress window is a window sized and positioned to meet building code requirements for emergency escape from sleeping rooms, basements, and certain other spaces, with minimum opening dimensions and maximum sill heights.
What is an Energy Star certified window?: Energy Star certified windows meet U.S. Environmental Protection Agency efficiency standards for windows in a specific climate zone, requiring performance thresholds for heat loss, solar gain, and air leakage.
What is an insulated glass unit (IGU)?: An insulated glass unit (IGU) is a sealed assembly of two or more glass panes separated by spacers and filled with air or inert gas to reduce heat transfer through windows.
What is an NFRC label?: An NFRC label is a standardized rating sticker on window units showing energy performance metrics including U-factor, Solar Heat Gain Coefficient, visible transmittance, and air leakage.
What is argon gas fill?: Argon gas fill is an inert gas sealed between the panes of a multi-pane window to slow heat transfer and improve thermal insulation compared to air-filled units.
What is full-frame vs insert window replacement?: Insert replacement installs a new window unit into an existing frame, while full-frame replacement removes the old frame entirely down to the studs and installs both new frame and sash.
What is impact-resistant laminated glass?: Glass panes bonded together by a resilient plastic interlayer (typically PVB or SGP) that keeps the glass intact when broken by impact, preventing shards from scattering.
What is Low-E glass?: Low-emissivity (Low-E) glass is window glazing coated with a thin metallic layer that reflects infrared heat back indoors while allowing visible light through, reducing heating and cooling loads.
What is Miami-Dade / Florida Building Code approval?: A Miami-Dade County testing and certification standard for impact-resistant windows and doors that demonstrates resistance to high winds and debris strike, used as a performance benchmark by manufacturers nationwide.
What is solar heat gain coefficient (SHGC)?: Solar heat gain coefficient (SHGC) is the fraction of incoming solar radiation that passes through a window and becomes heat inside, measured on a scale from 0 to 1.
What is the difference between bay windows and bow windows?: Bay windows extend outward in three flat panels set at angles (typically 90 to 120 degrees), while bow windows curve smoothly using four or more equal-radius panels.
What is window flashing?: Window flashing is a water-resistant material, typically metal or self-adhesive tape, installed around the perimeter of a window opening to direct moisture away from the frame and wall cavity.