Trim

The visible finishing work on the interior of a building includes all wood, metal or plastic ornamental parts used to cover joints between jambs and plaster around windows and doors may also include hardware.

Triple Glazing

Three panes of glass or plastic with two air spaces between.

Truss

A structural member utilizing triangular shapes to gain strength with a minimum amount of material.

Tube

A pipe that water flows through to transfer heat.

Tube Bundle

A group of heat exchanging tubes.

Turbulent Flow

Disturbed, chaotic flow of a fluid. The velocity at a given point varies erratically in magnitude and direction.

Two Phase Flow

Change in phase (liquid to gas, gas to liquid), due to changes in pressure or temperature, that takes place while the fluid is circulating through the heat exchanger.

UBC

Uniform Building Code.

U-Factor (U-Value)

A measure of the rate of non-solar heat loss or gain through a material or assembly. It is expressed in units of Btu/hr-sq ft-°F (W/sq m-°C). Values are normally given for NFRC/ASHRAE winter conditions of 0° F (18° C) outdoor temperature, 70° F (21° C) indoor temperature, 15 mph wind, and no solar load. The U-factor may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. The lower the U-factor, the greater a window's resistance to heat flow and the better its insulating value.

UL

Underwriters laboratories, inc.

UL Label

Label displayed on packaging to indicate the level of fire and/or wind resistance of asphalt roofing.

Ultrasonic Flow Meter 

A device that is used to measure flow through piping.

Ultraviolet

Invisible radiation waves with frequencies shorter than wave lengths of visible light and longer than X-Ray.

Ultraviolet Light (UV)

The invisible rays of the spectrum that are outside of the visible spectrum at its short-wavelength violet end. Ultraviolet rays are found in everyday sunlight and can cause fading of paint finishes, carpets, and fabrics.

Undercut

To cut away inner edges of a crack or hole in the shape of an inverted V in order to provide a stronger base for patching material.

Underfloor Crawl Space

The area within the confines of the foundation and between the ground and the underside of the lowest floor structural component.

Underfloor Wiring System

A system in which ducts or raceways are built into a floor to house electrical wiring.

Underlayment

The first layer of insulation placed under vinyl siding, usually made of foam.  Also asphalt saturated felt used beneath roofing to provide additional protection from the deck.

Underpinning

Timbers, steel beams or other temporary props used to support a foundation during construction also permanent supports installed to increase the load-bearing capacity of a foundation or wall.

Universal Motor

An electric motor which will operate on both AC and DC.

Up Flow

A type of furnace that draws cool air from the bottom and blows the warmed air out the top into the duct work. This type of furnace is usually installed in a basement or an out-of-the-way closet.

Urethane Foam

A type of insulation which is foamed in between inner and outer walls of display case.

Utility Room

A room that is designed or used for laundry, heating, equipment or related purposes.

Vacuum

A reduction in pressure below atmospheric pressure.  A space partially exhausted by artificial means (i.e., suction measured in inches of Hg in a low pressure chiller).

Vacuum Control Systems

In many automobile air conditioning systems, intake manifold vacuum is used to operate dampers and controls in system.

Vacuum Pump

A special high efficiency compressor used for creating high vacuums for testing or drying purposes.

Valley

The internal angle formed by the intersection of tow sloping roof planes.

Valve

Device in a heating or plumbing system that controls the flow of a liquid or gas.

Valve, Service"

A device used by service technicians to check pressures and charge refrigerating units.

Valve, Solenoid"

A valve actuated by magnetic action by means of an electrically energized coil.

Vapor Barrier

Any material used to prevent the passage of water vapor.

Vapor Retarder

A material that reduces the diffusion of water vapor across a building assembly.

Vaporize

To convert liquid into a gas, usually by application of heat.

Vapour/Vapor

A substance in gas form, particularly one near equilibrium with its condensed phase, which does not obey the ideal gas laws in general, any gas below its critical temperature.

Vapour/Vapor Barrier

A moisture impervious layer applied to the surfaces enclosing a space or to the surface of thermal insulation to limit moisture migration through the surface.

Variable Air Volume System

The air handling system that conditions the air to a constant temperature and varies the outside airflow to ensure thermal comfort. Ventilation air-defined as the total air, which is a combination of the air brought into the system from the outdoors and the air that is being recirculated within the building. Sometimes, however, used in reference only to the air brought into the system from the outdoors.

Variable Frequency Drive (VFD)

A chiller with a variable frequency drive has a controller that monitors the operating conditions and uses a combination of inlet guide vanes and speed control. Vfds act as a soft-starter. Vfds can offer significant energy savings at part load conditions, but they typically do not run as efficiently at full load when compared to constant speed drives.

Vault

A continuous length of arched ceiling.

VAV

An acronym for a Variable Air Volume system.

Vent

The movable framework or sash in a glazed window that is hinged or pivoted to swing open.  Any oriface in the floor or ceiling attached to ductwork for the purpose of supplying or circulating air in a forced air heating system. 

Vent Pipe

A small pipe that extends from gas heating fixtures to a vent stack in the roof, allowing exhaust gases to escape to the outer air i.e. duct, ductwork, duct system. 

Vent Sleeve

See collar