AAMA

American Architectural Manufacturers Association. A national trade association that establishes voluntary standards for the window, door, storefront, curtain wall, and skylight industries.

Absolute Humidity

Amount of moisture in the air, indicated in grains per cubic foot.

Absolute Pressure

Gauge pressure plus atmospheric pressure (14.7 lbs. Per sq. In.).

Absolute Temperature

Temperature measured from absolute zero.

Absorptance

The ratio of radiant energy absorbed to total incident radiant energy in a glazing system.

AC

Abbreviation for alternating current, a type of electric current in which the polarity is constantly reversing causing the electron flow to reverse.

AC Pressurization Technique

This technique allows building air tightness to be examined at small (<4 Pa) pressure differentials with minimal interference from climatic forces. The airflow through the building envelope can be evaluated by using a piston assembly to vary the effective volume of the structure. Measuring the amplitude of the pressure response inside the building and phase relationship between this pressure and the velocity of the piston enables the airflow through the building to be determined.

Accelerate

To add to speed hasten progress of development.

Acceptable Air Quality

Air in which there are no known contaminants at harmful concentrations as determined by specialist authorities and with which a substantial majority (80 % or more) of the people exposed do not express dissatisfaction. (ASHRAE 62-1989).

Accessible Hermetic

Assembly of motor and compressor inside a single housing unit.

Accumulator

Tank on the suction side of a system that holds excess refrigerant to prevent slugging the compressor with liquid.

Accumulator

Storage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line.

ACH (Air Changes Per Hour)

Unit used for quantifying airflow.

Acid Condition In System

Condition in which refrigerant or oil in system is mixed with fluids which are acid in nature.

Acidize 

When acid is used to remove mineral and iron deposits (scale) to restore heat transfer efficiency.

A-Coil

A heat exchanger consisting of two diagonal coils that are joined together in a manner that looks like the letter ""A"".

ACR Tubing

Tubing used in refrigeration which has ends to keep tubing clean and dry.

Acrylic

A thermoplastic with good weather resistance, shatter resistance, and optical clarity, used for glazing.

Activated Alumina

Chemical used as a drier or desiccant.

Activated Carbon

Specially processed carbon used as a filter-drier commonly used to clean air.

Active Solar Heating System

System in which solar energy is absorbed in a collector, stored, and distributed by an auxiliary circulating system.

Actuator

That portion of a regulating valve that converts mechanical fluid, thermal energy, or electrical energy into mechanical motion to open or close valve seats.

Adiabatic Compression

Compressing refrigerant gas without removing or adding heat.

Advanced Reciprocating Compressor

Type of compressor that uses a more efficient process for compressing refrigerant for better cooling efficiency.

Aeration

The act of combining a substance with air. Agitator-device used to cause motion in confined fluid.

Aerogel

A microporous, transparent silicate foam used as a glazing cavity fill material, offering possible U-values below 0.10 BTU/(h-sq ft-°F) or 0.56 W/(sq m-°C).

AFUE

Annual Fuel Utilization Efficiency. This number represents how efficiently a furnace converts fuel to energy. The higher the rating, the more fuel-efficient the furnace is. . For example, an AFUE of 90 means that 90% of the fuel is being used to warm your home, while the other 10% escapes as exhaust with the combustion gases. The government's established minimum rating for furnaces is 78%. 

AFUE%

Furnace Efficiency ""AFUE"" is a measure of a furnace's heating efficiency. It stands for Annual Fuel Utilization Efficiency. The higher the AFUE%, the more efficient the product

Air

A mixture of gases constituting a compressed fluid tied to the planet by gravitational attraction. Air on earth is 79.0% nitrogen, 20.9% oxygen, and less than 0.1% a mixture of carbon dioxide, argon, helium, and hundreds of other gases originating from natural and man-made sources. Air in the context of building simulation is often used to infer dry bulb temperature.

Air Balance Test

A test used to measure airflow across a tower or air handler system.

Air Balancing Hood

Measures airflow from grilles and diffusers.

Air Change

A quantity of fresh air equal to the volume of the room or building being ventilated.