Tankless water heater

Hot water heaters designed to provide instantaneous hot water, rather than storing preheated hot water in a tank. Such devices can serve an entire home, or be "point-of-use", serving an individual fixture (like a shower or sink). Benefits include elimination of "standby losses", or energy wasted keeping stored water warm, and with point of use devices, reduction or elimination of water wasted waiting for water to get warm, as well as conductive losses as water travels through pipes. Electric demand systems tend to use a large amount of energy; gas-fired units with standing pilot lights lose much of their efficiency due to the ongoing pilot light.

Task lighting

Lighting to provide illumination for a specific activity in a specific place.

Tax credit

A state or federal benefit paid through the tax system, which has the effect of increasing (rather than reducing) net income. A tax credit is generally more valuable than an equivalent tax deduction, or tax allowance, because a tax credit reduces tax directly, while a deduction or allowance only reduces taxable income and so the reduction in tax is only a fraction (the marginal tax rate) of the deduction or allowance.

Tax-shifting

The objective is to stop taxing the things we do want (like income and savings) and shift towards taxing things people collectively do not want (like waste and pollution). The current tax system encourages the depletion of natural resources and the unsustainable degradation of the environment, while discouraging job creation. Ideally, a shift toward taxing unwanted effects over desired ones, without increasing the total tax burden, will use market mechanisms to influence and reward more sustainable behavior without more government regulations.

Therm

A unit of heat energy equal to 100,000 British thermal units (BTU). It is approximately the energy equivalent of burning 100 cubic feet (often referred to as 1 Ccf) of natural gas at standard temperature and pressure.

Thermal break

An element of low conductance placed between elements of higher conductance to reduce the flow of heat. For example, a thermal break material, such as plastic, may be placed between the inner and outer parts of an aluminum window frame to make the window more energy efficient.

Thermal bridge

A highly conductive element such as a metal channel in the building envelope that penetrates or bypasses the less conductive element such as insulation, and acts as a thermal short circuit through the insulation system.

Thermal buffer

A space or other element that reduces the heating and cooling load on another space located between the space and the exterior.

Thermal chimney

A section of a building where solar heat or thermal currents are controlled and utilized to stimulate an updraft and exhaust hot air. This draws in fresh air through open windows or vents and is a passive cooling technique.

Thermal conductance

Ability of a material to allow heat to pass through it. Aluminum has high thermal conductance, insulation has low thermal conductance.

Thermal energy storage

Refers to a number of technologies that store energy in a thermal reservoir for later reuse. They can be employed to balance energy demand between day time (when rates are high) and night time (when rates are low). The principal application today is the production of ice, or chilled water at night, which is then used to cool environments during the day (peak energy demand). Thermal energy storage technologies also store heat, usually from active solar collectors, in an insulated repository for later use in space heating, domestic or process hot water, or to generate electricity. Most practical active solar heating systems have storage for a few hours to a day's worth of heat collected.

Thermal flywheel

A space or other element such as a solid masonry wall that collects heat during one period and releases it during another in a repetitive pattern.

Thermal mass

Materials that have a high capacity for absorbing heat, and change temperature slowly. These materials are used to absorb and retain solar energy during the daytime for release at night or during cloudy periods. They include water, rocks, concrete, masonry, and earth.

Thermal panel

A flat solar collector, such as a solar hot water or air panel used to heat water, air, or otherwise collect solar thermal energy.

Thermal storage capacity

The capacity for a building material to store heat internally from the sun, generally for later use or release.

TI

Tenant Improvement: refers to the build-out of a commercial interior.

Tight building

A building that is designed to let in minimal infiltration air in order to reduce heating and cooling energy costs. In actuality, buildings typically exhibit leakage that is on the same order as required ventilation; however, this leakage is not well distributed and cannot serve as a substitute for proper ventilation.

Tipping fees

Fees charged for dumping large quantities of trash into a land fill.

Topography

The physical features, including the configuration of a surface, of a place or region.

TND

Traditional Neighborhood Development: a basic unit of New Urbanism, which includes the following characteristics: a center that includes a public space and commercial enterprise; an identifiable edge, ideally a five-minute walk from the center; a mix of activities and variety of housing types; an interconnected network of streets and blocks usually laid out in a modified grid pattern; high priority to public space with prominently located civic buildings and open space that includes squares, plazas, and parks.

TPO

Thermoplastic Olefin: a polymeric membrane frequently found in outdoor applications such as single-ply roofing because it does not degrade under solar UV radiation. TPO can be recycled. Sheets are installed with mechanical fasteners.

Transition town (also Transition Network, Movement and Initiative)

The term was coined by Louise Rooney and then spread to Totnes, England where Rob Hopkins and Naresh Giangrande developed the concept during 2005 and 2006. The aim of this grassroots community project is to equip communities for the dual challenges of climate change and peak oil. The Transition Towns movement is an example of socioeconomic localization.

Transit-oriented development

A mixed-use community within an average 2,000-foot walking distance of a transit stop and core commercial area that mixes residential, retail, office, open space, and public uses in a way that makes it convenient for residents and employees to travel by transit, foot, bike, etc.

Triple bottom line

A business and development philosophy incorporating the three E’s: equity, environment, economics. Also referred to as the three P’s: people, planet, profit. This business model contrasts with the traditional model of focusing on economics or profit.

Trombe wall

A thermal storage system used in passive solar design. A high-mass wall that stores heat from solar gain during the day and slowly radiates the heat back into the living space at night.

Truth window/wall

An exposed section, or “window” of a wall that reveals the layered components within it.