Vampire (or Phantom) Load

The amount of energy a device consumes while in standby mode or switched “off.”

Vapor Barrier

A building material that resists the passage of invisible moisture in the air. Barriers are usually plastic film, metallic foil or asphalt-coated felt.


Any opening in a building designed for the flow of air or moisture.


The process of supplying or removing air by natural or mechanical means to or from any space. Such air may or may not have been conditioned.


The push that moves electric current through a conductor.