Brochure

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Dry bulb temperature: Measurement of sensible
heat.
Economizer: A mechanical device that makes
system adjustments in response to changing
conditions in order to maximize energy efficiency.
An economizer typically contains a thermostat
control that opens the dampers when outside air
temperatures are lower than indoors, providing
“free cooling”. Many economizers will incorporate
humidity sensors to ensure outside air is both cool
and dry enough to allow indoors, unconditioned.
Emissivity: The efficiency with which the surface
material of a certain object emits energy. Emissiv-
ity is an important consideration in using infrared
to measure temperatures on reflective surfaces.
Enthalpy: (h) Total heat contained in a substance,
which is the sum of sensible heat and latent heat.
Evaporator coil: Cools and dehumidifies the air
by converting liquid refrigerant into a gas, which
absorbs the heat from the air.
Exfiltration: The controlled or uncontrolled move-
ment of air out of a building, through cracks, and
other openings.
Exhaust air: Air that is removed from a space, and
not recirculated into the system.
Exhaust ventilation: Mechanical removal of air
from a portion of a building (e.g., piece of equip-
ment, room, or general area).
Fan coil: A component of a heat pump system, used
to provide additional heat when the heat pump
does not provide adequate heating.
Filter efficiency: The ratio of particles trapped by
filter media compared to the total number of par-
ticles found in the air upstream of the filter.
Filter, HEPA: High-efficiency particulate arrestance
(HEPA) filter that is at least 99.97 percent efficient
in removing particulate matter with a diameter of
0.3 micrometers or greater.
Flame rod: Combustion safety control that conducts
electricity through a flame for flame detection.
Forced-air heating system: Uses air to carry heat.
Fungi: Any of a group of parasitic lower plants that
lack chlorophyll, including molds and mildews.
Green buildings: The building industry is increas-
ingly focused on making its buildings “greener,”
which includes using healthier, less polluting and
more resource-efficient practices. Indoor envi-
ronmental quality (IEQ) refers to the quality of
the air and environment inside buildings, based
on pollutant concentrations and conditions that
can affect the health, comfort and performance of
occupants—including temperature, relative humid
-
ity, light, sound, and other factors. Good IEQ is an
essential component of any building, especially a
green building.
Heat exchanger: Material that transfers heat from
one substance to another without allowing the
substances to mix.
Heat pump: Mechanical compression refrigeration
system that contains devices and controls that
reverse the flow of refrigerant. Reversing the flow
of refrigerant switches the relative position of the
evaporator and condenser.
Heat: Form of energy identified by temperature
difference or a change of state.
HEPA: High efficiency particulate arrestance (filters).
Hydronic heating system: Heating system that
uses water, steam, or other fluid to carry heat from
the point of generation to the point of use.
Indoor air pollutant: Particles and dust, fibers,
mists, bioaerosols, and gases or vapors.
Infiltration air: Air that flows into a building when
outer doors are open or when air leaks in through
cracks around doors, windows, or other openings.
Laminar air flow: Streamlined airflow in which
the entire mass of air within a designated space
moves with uniform velocity in one direction
along parallel flow lines with minimal mixing.
Latent heat: Heat identified by a change of state
and no temperature change.
Load: The amount of heat imposed on a refriger-
ant system, or the required rate of heat removal
in order to maintain a constant temperature in a
building. Typically expressed as a unit of heat per
unit of time (i.e. BTU/hr).
Makeup air: Air that is used to replace air that
is lost to exhaust.
Mixed air: A combination of return air and
outside air, prior to conditioning and being
supplied to the building.
Negative pressure: Condition that exists when
less air is supplied to a space than is exhausted
from the space, so the air pressure within that
space is less than that in surrounding areas.
Under this condition, if an opening exists, air will
flow from surrounding areas into the negatively
pressurized space.
Organic compounds: Chemicals that contain
carbon. Volatile organic compounds vaporize at
room temperature and pressure. They are found in
many indoor sources, including common house-
hold products, and building materials.
Outdoor air supply: Air brought into a building
from the outdoors (often through the ventilation
system) that has not been previously circulated
through the system. Also known as “Make-up Air.”