HVAC and BEMS

A material that retards the movement of water vapour through a building element (walls, ceilings) and prevents insulation and structural wood from becoming damp and metals from corroding.  Often applied to insulation batts or separately in the form of treated papers, plastic sheets, and metallic foils.

A HVAC system that has a stable supply-air temperature and varies the air flow rate to meet the temperature requirements.  Compared to the CAV systems, these systems waste less energy through unnecessarily high fan speeds.  Most new commercial buildings have VAV systems.

Used to regulate a motor's speed by varying the frequency being sent to the connected motor.  VSDs are used in a variety of applications to increase efficiency, save energy, and improve performance.  VSDs are also known as Variable Frequency Drives (VFDs).

A component of a heating or ventilation appliance used to conduct fresh air into, or waste air or combustion gases out of, an appliance or interior space.

HVAC term for a device mounted in the vent connector that closes the vent when the heating unit is not firing.  This traps heat inside the heating system and house rather than letting it draft up and out the vent system.

A tube in which combustion gases from a combustion appliance are vented out of the appliance to the outdoors.

A type of combustion heating appliance in which the combustion gases are vented to the outside, either with a fan (forced) or by natural convection.

The process of moving air (changing) into and out of an interior space either by natural or mechanically induced (forced) means.

Defined as the total air, which is a combination of the air brought inside from outdoors and the air that is being re-circulated within the building.  Sometimes, however, used in reference only to the air brought into the system from the outdoors; this document defines this air as "outdoor air ventilation".

The rate at which indoor air enters and leaves a building.  Expressed in one (1) of two (2) ways: the number of changes of outdoor air per unit of time (air changes per hour, or ACH) or the rate at which a volume of outdoor air enters per unit of time (cubic feet per minute, or CFM).