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Tamarack Cape Backdraft Damper
One Way Air Flow Valve
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The Cape Backdraft Damper is the ultimate one way air flow valve, designed to overcome
the inefficiencies and limitations of traditional gravity or butterfly dampers.
Click on either
image below for a larger picture.
The Cape Damper consists of a specially formulated fabric sleeve attached to an outer metal
sleeve. The fabric sleeve will allow air to pass through in the desired
direction of flow with miniscule reduction in airflow. For reverse airflow, airflow that should be
stopped by a backdraft damper, the Cape Damper gives a better seal at a lower
pressure and holds that seal as the pressure increases. The Cape Damper is quiet, with no metal clanging
sounds, and can be installed in a horizontal or vertical orientation. It is
available in five sizes, 4", 5", 6", 7" and 8".
The Cape Damper was tested against two other dampers at a moderate airflow, the kind of
airflow in a residential application. First the fan was run through
plain duct to set the desired airflow. Then each type of damper was inserted
into the same duct to measure the airflow.
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Product
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Resulting Airflow in CFM
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6" duct, 4" length
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80
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Butterfly Damper
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17
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Gravity Damper
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30
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Cape Damper
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77
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The other dampers decrease system efficiency by adding static
pressure in the direction of desired airflow. For reverse airflow, the same test was used.
Because all of these dampers are reasonably effective at stopping air, the next chart compares
leakage rates at various pressures.
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Leakage in CFM @ Inches/wg
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Product
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-.10"wg
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-.080
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-.052
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-.036
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-.018
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Butterfly Damper
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1.6 CFM
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2.0
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1.6
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1.2
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1.0
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Gravity Damper
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3.0
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4.0
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5.0
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5.0
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5.0
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Cape Damper
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0.4
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2.0
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2.0
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2.0
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2.0
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The Cape Damper works as well or better than other dampers at stopping undesired airflow. The Cape
Backdraft Damper is far superior at allowing unrestricted airflow in the desired direction of flow;
it doesn't steal away system efficiency. The Cape Damper is quiet, no metal clanging sounds and it
can be installed in a horizontal or vertical orientation.
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