Proper installation
and maintenance of HVAC duct work is directly related to the way a heating and air
conditioning system works. The efficiency of a new system or an existing one
depends on the quality of the ductwork.
Ductwork is a series of hollow,
insulated conduit that forms a network to deliver conditioned air through the
vents in a home/building. Typically, it is in the
attic where temperatures reach extremes of hot and cold.
A study by the US Department
of Energy (DOE) reports that typical duct systems in homes/buildings lose from 25 to 40 percent of the energy that is
intended for heating or cooling purposes.
Common problems with HVAC Ducts
- Insulation
- Design Defects
- Leaks
- Wasteful practices
- Replacement systems
The old adage that
“out of sight is out of mind” offers a caution that home/building owners may heed to an advantage. Many defects can
develop over time, and some may have occurred at the time of the original
installation. Any defect can make an air conditioning system less effective and
more expensive to operate.
1.
Insulation of Ducts
The insulation in the
ducts may not have the capacity to withstand temperatures in attic
spaces that can easily reach 100 degrees or more and zero degrees or less. The
prevailing temperature can permeate ducts that are not adequately insulated.
The resulting condition allows the air that is too hot or too cold to pass
directly into the home/building.
2.
Design defects in Ducts
Many homes/buildings use duct systems that were not properly
engineered or designed to distribute air evenly, unlike systems used in
commercial buildings. As a result, home/building owners have rooms that are uncomfortably hot, cold
or humid.
A contractor
can make a visual inspection of the configuration, but specialized equipment
can offer a more precise diagnosis. An air flow capture device that resembles a
hood may provide details about the effectiveness of the design and identify any
defects.
Hidden restrictions
within the ducts can impede the flow of air. Some electric utility
studies have shown that more than two-thirds of private residences were found
to have restrictions in air flow. Ducts are not intended to serve as attic
storage areas, and they react poorly to the weight of boxes that are stored on
top of them. If the weight causes the sections of duct to separate, it creates
an obvious problem. However, if the weight even slightly compresses the
interior area of the duct, the volume of air that can pass through is
significantly reduced.
3.
Leaks in Ducts
Taped joints are
frequently the place where leaks occur. DOE found that the grey tape
typically used on joints dries out rapidly and loses its ability to form a
seal. Leaks not only let air escape but also allow contaminants to enter. Dust
and mold that accumulate in the attic can enter the ducts and the air inside,
possible conveying health concerns to people and pets.
For many systems, the
loss of air through leaks is the cause of the most common type of problem.
Leaks reduce the cooling and heating capacity of any system, and they reduce
the output as well. A rate of air flow that is too high can force more air out
through the leaks. A contractor can test the air flow after repairs are made to
fix the leaks and make adjustments as needed.
For existing systems,
the DOE suggests that repairs to faulty ductwork are among the best ways
to improve energy efficiency. Contractors can check a duct system for air flow
and leaks. Tests may include the use of computerized instruments and gauges as
well as other equipment to determine the condition of the ducts.
4.
Wasteful practices
The energy that is
wasted through faulty duct systems often goes unnoticed until it causes an
increase in the utility bill. Inefficiency results from the uneven distribution
of conditioned air, creating areas in a home/building that are either too hot or too cold.
5.
Replacement systems
Many times, home/building owners buy new air conditioning systems a lack of
understanding that the duct system is at fault and not the unit itself.
Duct problems are
frequently the reason an existing systems seems unable to work efficiently.
Systems may meet the demands of the home/building as to sizing requirements, but ducts that waste
energy make them appear inadequate and in need of replacement.
A new air
conditioning system that uses a poor quality hvac ductwork / hvac duct
system has almost no chance to provide the maximum efficiency in heating
or cooling a home/building. When thousands of dollars
are required for the purchase of a new air conditioning system, the status of
the ductwork is an important fact to consider. Wasteful spending may result
from a lack of understanding of how ductwork affects the performance of HVAC
systems.
