A (23) B (23) C (41) D (27) E (28) F (15) G (12) H (21) I (20) K (5) L (11) M (16) N (15) O (11) P (21) R (22) S (37) T (14) U (12) V (11) W (10)
Tandem Wiring

A wiring option in which a ballast is shared by two or more luminaires. This reduces labor, materials, and energy costs.


Thermal efficiency.

Temperature Reset Controllers

Controls that automatically reset supply water temperatures by representative building loads (including return water temperature) or by outside air temperature.

Thermal Block

A collection of one or more HVAC zones grouped together for simulation purposes. Spaces need not be contiguous to be combined within a single thermal block.

Thermal Bridge

A component, or assembly of components, in a building envelope through which heat is transferred at a substantially higher rate than through the surrounding envelope area.

Thermal Conductance

Time rate of heat flow through a body (frequently per unit area) from one of its bounding surfaces to the other for a unit temperature difference between the two surfaces, under steady conditions (Btu/h x ft² x °F) [W/(m² x K)].

Thermal Resistance (R)

The reciprocal of the time rate of heat flow through a unit area induced by a unit temperature difference between two defined surfaces of material or construction under steady-state conditions.

Thermal Transmittance

The coefficient of heat transmission (air to air). It is the time rate of heat flow per unit area and unit temperature difference between the warm-side and cold-side air films (Btu/h x ft² x °F) [W/(m² x K)]. The U-factor applies to combinations of different materials used in series along the heat flowpath, single materials that comprise a building section, cavity air spaces and surface air films on both sides of a building element.


An automatic control device responsive to temperature.

Thermostat Setback

Usually done at night to reduce the amount of conditioning provided at night by allowing the interior temperature to drift naturally to a marginal temperature and then to recondition it to normal conditions in the morning.


(As applied to fenestration) bronze, green, blue, or gray coloring that is integral with the glazing material. Tinting does not include surface applied films such as reflective coatings, applied either in the field or during the manufacturing process.

Trade-Off Approach

A trade-off approach involves trading enhanced energy efficiency in one component against decreased energy efficiency in another component. These trade-offs typically occur within major building systems (e.g. envelope, mechanical) or in commercial lighting.


A piece of electrical equipment used to convert electric power from one voltage to another voltage.

Transverse Seam

All duct seams other than the longitudinal seam (which runs parallel to the direction of air flow).