Visible Transmittance (VT)

Related terms

• Weatherstripping

  Compressible seals around a door or operable window perimeter that block air and water infiltration. A cheap, high-impact efficiency item.

• Vinyl Window

  A PVC-framed window — low cost, low maintenance, good insulation. The dominant residential replacement material; quality varies widely by…

• Weep Hole

  A small opening in the bottom of a window frame or sill that drains incidental water to the exterior. Blocked weeps cause leaks and rot.

• U-Factor

  The rate of non-solar heat flow through a window; lower means better insulation. The primary winter-performance metric on the NFRC label.

• Wood Window

  A traditional wood-framed window with the best natural insulation and classic look but the highest maintenance unless clad.

• Triple-Pane / Triple-Glazed

  A three-pane insulated unit with two gas-filled cavities for superior insulation and sound control, used in cold climates and high-perfor…

• Transom

  A window above a door or window, fixed or operable, adding daylight and architectural detail.

• Threshold

  The bottom member of an exterior door opening, often adjustable, that works with the door bottom and sweep to seal out water and air.