Duct Blaster
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Summary
There are over a
million miles of forced-air ductwork in American homes. If ducts leak-and they
do-energy is wasted. Leaky ducts can significantly increase energy needed for
heating and cooling. Leaky supply ducts can send expensive conditioned air into
unconditioned spaces such as attics and crawlspaces and leaky return ducts draw
unconditioned air into the duct system. Simple duct sealing methods can save
energy and increase homeowner comfort.
Duct leakage
measurements are used to diagnose duct leakage problems, estimate energy loss
from duct leaks, and verify the quality of duct system installation. A Duct
Blaster is one diagnostic tool used by energy professionals to determine how
leaky, or energy-inefficient, a duct system is.
Details
A Duct Blaster
consists of a calibrated fan capable of
blowing up to 1500
cubic feet per minute (CFM) of air,
a pressure tap, and
flexible ducting for hook-up with a
duct system. It can
accurately measure duct leakage
rates of between 20
and 1500 CFM. The entire unit
weight less than 10
pounds. Duct leakage testing can
quickly determine the
quality of ductwork installation.
Installation
To perform a duct
leakage test, an energy professional connects a Duct Blaster to a duct system
at the air handler or a central return grille. All other return grilles and
supply registers are temporarily sealed. The Duct Blaster fan is turned on and
flow is increased until the duct system is pressurized to the specified test
pressure (typically 25 Pascals). The contractor measures leakage rate using an
airflow and pressure gauge. If desired, theatrical fog can be injected in the
systems to determine the exact location of leaks and to demonstrate duct
leakage to homeowners. The Duct Blaster's calibrated fan takes precise
measurements of leakiness from 20 to 1500 CFM.
Benefits/Costs
The Duct Blaster is a
relatively inexpensive, simple, and accurate diagnostic method that requires
only one piece of equipment. Low flows can be measured precisely. Tests can be
performed on new homes before drywall is installed--making duct sealing an
easier task.
Studies estimate that
fixing leaky ductwork can save up to 25 percent on energy costs.
Limitations
The Duct Blaster
measures total duct leakage and cannot separate leaks to the outside from leaks
to conditioned spaces unless combined with a whole-house pressurization.
Code/Regulatory
Duct Blaster equipment
and gauges meet ASTM Standards E779-87 and 152-P, and CGSB-149.10-M86.
Availability
Contractors nationwide
can conduct airtightness testing. A list of experienced contractors can be
obtained from the manufacturer. Many utilities conduct duct leakage testing.
Contact(s)
If you have a specific
questions about this technology and/or its applications, please contact the
following resources.
The Energy
Conservatory
5158 Bloomington Ave.
South
Minneapolis, MN 55417
612/827-1117
http://www.energyconservatory.com/
Home Energy Magazine
Contains series of
articles on duct sealing, diagnostics, and installation.
Fact Sheet Source
The material provided
in this section is used with permission by the National Association of Home
Builders Research Center and the Partnership for Advancing Technology in
Housing (PATH).
Web sites: