HVAC GLOSSARY - V

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Valves: Components inserted into air ducts or devices which permit modification of the air resistance of the system and consequently a complete shut-off of the air flow (control valves).

VAV System: (Variable Air Volume System) A mechanical HVAC system capable of serving multiple zones which controls the temperature maintained in a zone by controlling the amount of heated or cooled air supplied to the zone.

VAV: (Variable Air Volume) Variable Air Volume.

Ventilation: 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 or treated.

Ventilation Air: Defined as the total air, which is a combination of the air brought inside from outdoors and the air that is being recirculated within the building.

Ventilation effectiveness: A measure of the fraction or percentage of outdoor air that reaches the occupied zone of a specified area; an evaluation of air delivery to occupants, regardless of the effectiveness of contaminant removal.

Ventilation efficiency: An evaluation of the pollutant removal capacity of a ventilation system.

Ventilation Rate: The rate at which indoor air enters and leaves a building. Expressed in one of two 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").

Ventilation standard: A specification for the minimum rate of input of outdoor air into indoor spaces.

VFD: (Variable Frequency Drive) Electronic speed control for motors.

Volatile Organic Compounds:(VOCs) One of a class of chemical compounds; indoor sources include tobacco smoke, building products, furnishings, cleaning materials, solvents, and office supplies. In sufficient quantities, VOCs can cause eye, nose, and throat irritations; dizziness; and headaches. Some VOCs are suspected carcinogens. Data for health effects resulting from exposure to the characteristically low levels of VOCs in the indoor environment are scarce. Compounds that vaporize (become a gas) at room temperature. Common sources which may emit VOCs into indoor air include housekeeping and maintenance products and building and furnishing materials. In sufficient quantities, VOCs can cause eye, nose, and throat irritations, headaches, dizziness, visual disorders, memory impairment; some are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.

Volt: A unit of electromotive force. It is the amount of force required to drive a steady current of one ampere through a resistance of one ohm. Electrical systems of most homes and office have 120 volts.