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Indoor Air Quality
Air Flow Measuring Control Damper
IAQ-42
April
2006
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Why is outside air measurement important?
There are many signifi cant benefi ts to monitoring outside air volumes. First, by measuring the amount of
outside air coming into a building you can be assured that the building is complying with all applicable
indoor air quality codes including ASHRAE Standard 62 and California Title 24. Meeting these minimum
requirements reduces indoor airborne viruses and bacteria which can lead to Sick Building Syndrome.
Studies have shown that buildings that are under ventilated suffer from reduced productivity levels.
The second major advantage to monitoring outside air volumes is that it eliminates costly over ventilation. In
addition to increased energy costs associated with heating and cooling of outside air, over ventilation causes
in an increase in humidity that can result in mold development.
Where should an air measuring damper be used?
Exhaust Air
Mixed Air
Outside Air
Exhaust Air
In this application an air measuring control damper is used to measure and control outdoor air intake while a
second air measuring control damper is used to measure and control the exhaust fl ow. The set point for the
exhaust air damper would track the fl ow of the outdoor air damper (minus a differential if positive building
pressure is desired.)
Mixed Air
In this application, an air measuring control damper is used to measure and control outdoor air intake while
a second air measuring control damper is used to control the mixed air temperature. Normally an averaging
sensor is required for mixed-air temperature control because the large temperature differences between
return air and outdoor air cause stratifi cation. The mixed air temperature is calculated from the fl ows and
temperatures measured by each damper eliminating the measurement problem caused by stratifi cation.
Outside Air
In this application, an air measuring control damper provides outdoor air control based on a demand signal.
The demand signal could be determined by a set schedule or by occupancy sensors. Examples of demand
signals are carbon dioxide (CO2) concentration, a binary signal from a motion detector, or a manual switch.
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What is the IAQ-42?
Greenheck’s IAQ-42 is an air measuring control damper that utilizes patented Specifl ow™ technology. The
IAQ-42 will control air to prevent over-ventilation, provide energy savings during periods of low occupancy,
and prevent under-ventilation not meeting ASHRAE Standard 62. The Specifl ow™ technology built into the
controller measures the pressure, position of the damper blades, and the temperature of the air fl owing
through the damper.
The IAQ-42 can help buildings meet the minimum outdoor air requirements of ASHRAE Standard 62 or
California Title 24 by providing accurate monitoring and control of outside air. You can earn LEED-EB credits
for air monitoring, increased ventilation, and ultra low leakage.
The IAQ-42 meets IECC (International Energy Conservation Code®) requirements with a leakage rating of
3 cfm/sq. ft. @ 1 in. wg (55cmh/m2 @ .25 kPa) or less.
The IAQ-42 is provided
with a factory supplied
honeycomb air straightener.
When ordering an IAQ-42
with an optional 4 inch
(101mm) or 6 inch (152mm)
louver it does not require an
airfl ow straightener.
The air pressure pickups
are designed to be
mounted on the blades.
Temperature sensors
monitor air temperature
to allow the controller to
correct the airfl ow rate
for changes in air density.
Every damper is provided with
a 24 Vac modulating actuator
to control the damper’s blade
position and provide feedback
to the controller. The actuator
can be mounted externally or
internally.
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Why is Factory Calibration Important?
Every IAQ-42 damper is factory calibrated in
our accredited testing facility before shipping.
Greenheck provides a certifi cation chart with every
damper. By calibrating each damper, you can be
assured of the most accurate airfl ow readings
possible.
The IAQ-42 is available with or without a factory
calibrated controller. The Specifl ow™ technology
built into the controller measures the pressure,
position of the damper blades, and the temperature
of the air fl owing through the damper. From these
readings, the controller computes the airfl ow rate
and adjusts the damper blades accordingly.
What’s the benefi t of the IAQ-42 over the competition?
The IAQ-42 has a number of advantages over the competition:
• By integrating the pressure pickups with the control damper, the pressure signal is increased at low
velocities making the unit more accurate in non-uniform fl ow conditions.
• Locating the pickups on the blade amplifi es the pressure signal which increases the accuracy of
readings.
• The pickups can easily be repaired or replaced.
• The small size of the pickups add minimal pressure drop to the system.
• The controller with Specifl ow™ technology automatically compensates for the effect of air
temperature on air density.
• The controller with Specifl ow™ technology can operate stand alone or integrated with a DDC building
control system.
This table shows the benefi ts of the IAQ-42 versus competitor’s models.
Benefi ts
Low pressure drop
Low velocity
accuracy
Temperature
compensated
Insensitive to
condensation
Integral controller
Factory calibrated
No additional
duct work required
Easily maintainable
Insensitive to
non-uniform fl ow
Greenheck
IAQ-42
99 9
99
99
99 9
99 9
99
99
99
99
Ruskin
IAQ50
Trane Traq™
Damper
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Why is temperature compensation important?
Airflow measurement accuracy is dependent on the density of the air being measured and in turn air
density is a function of temperature. The IAQ-42 monitors the dry-bulb temperature of the air passing
through it and corrects the air density used to calculate the airflow rate. Airflow measuring devices that do
not compensate for changes in air density must assume a “standard” density to calculate an airflow rate.
As air heats up it gets lighter. If this change in air density is not taken into consideration the monitoring
device will allow too much hot outside air into the building, thus unnecessarily increasing the cooling
load. On a hot summer day outside air temperatures coming off of a black tar roof can easily reach over
120° F (49° C). Without temperature compensation, an airflow-monitoring device would be telling the
system to allow about 5% more air into the building than is desired. For an air-handler with an outside
air design load of 20,000 cfm (101 m/s), this could cost a facility $500 per year. In parts of the country
where dynamic utility rates will be used, the penalty for a 20,000 cfm (101 m/s) outdoor air load would
be $750 per year. In addition to increasing energy costs, over-ventilation in humid climates could cause
excessively high indoor humidity, which could promote the growth of mold.
The opposite is true as air cools down and gets heavier. In cold climates outside air temperatures can
reach –40° F (-40° C). This condition can lead to under-ventilation. An airflow-measuring device that does
not compensate for temperature changes would measure 11% more outside air than is actually coming
into the building. Under-ventilation from lack of temperature compensation will occur at the same time as
cold and flu season.
IAQ-42 can save you space!
In a typical ventilation system, there is a separate damper and airfl ow monitor. The airfl ow monitor needs
to be a certain distance from the damper (formula driven).
The IAQ-42 with a straightener is mounted in a sleeve; the spacing doesn’t change based on the size that
you need. The total space required is 12 inches (305mm)! The IAQ-42 with a 4 inch (101mm) or 6 inch
(152mm) louver needs 16 inches (406mm) of space.
Example:
If the opening is 36 inches W x 36 inches H (914mm x 914mm), the space between the damper and airfl ow
monitor would be 18 inches (457mm). If you add in the damper depth, 5 inches (127mm), and air monitor
depth, 8 inches (203mm), you would need 31 inches (787mm) of space.
The IAQ-42 with straightener takes only 12 inches (305mm) of space and it doesn’t change! That saves 19
inches (483mm) of space!
IAQ-42 with straightener requires a 12 inch
(305mm) sleeve.
IAQ-42 with a 4 or 6 inch (101 or 152mm)
louver requires a 16 inch (406mm) sleeve.
IAQ-42 is available with louver models
ESD-635, ESJ-401LT, or EHV-602.
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More Energy saving products
from Greenheck!
The following models meet IECC (International Energy Conservation Code)
requirements of damper leakage of 3 cfm/sq. ft @ 1 in. wg or less:
VCD-33
VCD-34
SEVCD-33
VCD-40
VCD-42
VCD-43
ICD-45
The Greenheck Difference
What makes Greenheck different from other damper manufacturers?
Perhaps it’s having the most UL-certified dampers, or the industry-
leading testing capabilities. Most Greenheck dampers meet California
State Fire Marshal and NY MEA requirements. Aggressive research
and development also keeps Greenheck a major player in the damper
industry.
Unparalleled In-house Testing
Capabilities
State-of-the-art testing facilities have always been important to Greenheck’s
continuing business success. We have laboratory facilities devoted to the latest
development and testing of damper products to the latest versions of AMCA,
ASHRAE, UL, and other industry standards of performance.
Every IAQ-42 damper is factory calibrated in our accredited testing facility before
shipping. Greenheck provides a certifi cation chart with every damper.
Leading Edge Technical Support
All Greenheck products are supported by the industry’s best product
literature, electronic media, and Computer Aided Product Selection program
(CAPS). You’ll also find extensive information on the internet.
You can always count on the personal service and expertise of our national
and international representative organizations. To locate your nearest
Greenheck representative, call 715-359-6171, or visit our website at
For more information on energy saving programs:
www.usgbc.com - United States Green Building Council
www.energycodes.gov - U.S. Department of Energy Building Energy Codes Program
www.energystar.gov - Energy Star
www.epa.gov - U.S. Environmental Protection Agency
www.greenseal.org - Green Seal
Our Warranty
Greenheck warrants this equipment to be free from defects in material and workmanship for a period of one year
from the purchase date. Any units or parts which prove defective during the warranty period will be replaced at
our option when returned to our factory, transportation prepaid. Motors are warranted by the motor manufacturer
for a period of one year. Should motors furnished by Greenheck prove defective during this period, they should
be returned to the nearest authorized motor service station. Greenheck will not be responsible for any removal or
installation costs.
As a result of our commitment to continuous improvement, Greenheck reserves the right to change specifications
without notice.
Greenheck P.O. Box 410 • Schofield, WI 54476-0410 • Phone (715) 359-6171 • greenheck.com
IAQ Catalog Rev. 1 April 2006 RG Copyright © 2006 Greenheck Fan Corp.
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