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Tamarack Cape Backdraft Damper
One Way Air Flow Valve for whole house fans
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.
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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
| Product |
-.10"wg |
-.080 |
-.052 |
-.036 |
-.018 |
| Butterfly Damper |
1.6 CFM |
2.0 |
1.6 |
1.2 |
1.0 |
| Gravity Damper |
3.0 |
4.0 |
5.0 |
5.0 |
5.0 |
| Cape Damper |
0.4 |
2.0 |
2.0 |
2.0 |
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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