Neutral Pressure Plane:  The imaginary horizontal line within the house where; below this line the house is drawing air in and above this line the house is blowing air out.

Stack Effect:  The effect of warm air rising and escaping the living area of the house.  This air must be replaced by drawing air in below the neutral pressure plane.  This effect is magnified in higher buildings

Blower Door:  A tool that installs within an existing door frame and is used to depressurize or pressurize the home to determine air leakage.  The blower door is used to determine natural air changes per hour (NACH).

Natural Air Changes per Hour:  The number of times the air in replaced with air from the outside during an hour.  Currently building scientists think that 0.35 NACH is the ideal number.  This is a measurement of air infiltration.

Air Infiltration:  The process of drawing air into the house through cracks, gaps, and unintentional (or intentional) holes within the shell of the house.

Shell:  The exterior potions of the house that define the living space

Living space:  The areas in the home that are intended to be occupied.

Caulk:  Pliable and moldable materials used to fill small cracks and voids to provide an air and/or water tight seal.  Usually latex, siliconized latex, or polyurethane materials.

Weatherstripping:  Any number of materials used to make a connection point air or water tight.  These materials can be single part or multipart fabricated pieces designed for a specific window, door, or application.

EnergyStar:  A nationally recognized brand name provided by the Environmental Protection Agency.  Products that have this brand meet specific and strict energy use criteria designed for that type of product.

Indoor Air Quality:  A term used to describe the quality of the air within a house.  Typically this term is not used for commercial buildings (industrial hygiene is used in commercial and industrial property).