Water in the form of gas. Water vapor is transported by air movement caused by pressure differences.

  Annual Fuel Utilization Efficiency

  The barrier that prevents infiltration of outdoor air into the conditioned space and exfiltration of indoor air to the outside. Also known as “pressure boundary”, it should be continuous and aligned [..]

  A hollow conduit or tube (square or round) that circulates air from a forced-air heating and/or cooling system to a room (supply duct) or returns air back to the main system from a room (return duct [..]

  A hole, crack, or gap where air can leak in or out of a house. Air leaks can make a home feel drafty or uncomfortable and waste energy.

The process of sealing bypass ducts in the pressure boundary to prevent air leakage. Air sealing reduces heat flow from air movement and prevents water vapor from entering the wall.

Heat-resistant material used previously in many building products; represents serious health hazard as an airborne particulate.

  Negative vent pressure that uses standard chimney to remove combustion by-products from the home.

  An air connection between the living space and the attic.

  Intended to remove heat and moisture from attic areas to the outside.