Energy Solutions  Newsletter

 

Who Should Be Interested?

"Anyone who rents or owns a residential or commercial space should be interested in duct testing and sealing as it will improve efficiency of heating and cooling equipment, enhance air distribution, and reduce air borne contaminants", according to Rich Gajarsky, Operations Manager at the Richmond-based Sustainable Technology Institute (www.sustainabletechnologyinstitute.com). 

 

Ralph Joyce, Energy Conservation Program Manager at Dominion added: "Dominion's Non-Residential Duct Testing and Sealing Program is an easy way for customers to save energy and create a more comfortable work environment for their employees and customers."

 

Who Can Do the Work?

When asked who can do the duct testing and sealing, Gajarsky replied: "Only experienced contractors who are trained and licensed in the field of HVAC duct sealing should be sought for testing and sealing. A reputable contractor will hold credentials in the energy efficiency and building diagnostics fields as well as a proven track record they can validate with list of references".

 

What is It?

When asked to describe duct testing and sealing, Richard A. Hansen, PE, Mechanical Engineer at Core-Technical Mechanical Engineer (www.Core-Technical.com) said: "Duct Air Leakage Testing (often abbreviated "DALT") is a process by which air is forced at a known rate into a section of duct work that has been isolated from the rest of its system.  The rate that air is able to flow into the section is equal to the rate at which air is leaking from that section.  This leakage rate and an associated pressure reading are used, along with information about the size and shape of the ductwork, to determine several different metrics.  These metrics are used to characterize what proportion of the air fed into the duct will emerge where it is needed."

 

Hansen continued: "Duct sealing is the process by which leakage points in ductwork (frequently seams, screw penetrations or joints) are coated with specifically formulated compounds or wrapped with specialized tape in order to lessen the leakage rate of the ductwork.  After duct sealing is performed, DALT is usually repeated in order to prove that the treatment has achieved the desired result".

 

When?

Hansen and Gajarsky agreed that ideally,duct testing and sealing should be performed when the ductwork is installed.  Of course duct work can be tested at any time.  Even new duct work may leak if not tested and sealed properly during construction.  Hansen recommends testing on at least a 10 year cycle.

 

Where?

When asked where duct testing and sealing takes place, Hansen added:  "Duct leakage testing and sealing occur wherever there is accessible ductwork.  This is frequently located above drop ceilings in commercial office space, but exposed ductwork in office spaces has been increasing in popularity as a design choice in recent years."  Gajarsky replied:  "Most testing is performed in the conditioned space with test equipment connected to the grills and vents of the system. In the case of a drop ceiling, duct work will be accessed from ladders that allow workers to reach the duct system within ceiling."

 

Why?

According to Gajarsky: "There are several important reasons that duct testing and sealing should be performed. First of all, without testing, we really don't know how our ductwork is performing. Secondly, holes in the duct system are a direct correlation to increased energy bills, longer equipment run times, shorter equipment life-span, and the introduction of contaminants."

 

Hansen says: "Duct Leakage is a matter of persistent loss.  If 10% of the air that is being sent through a duct never reaches its destination, a number of other things are happening:

• 10% of the energy that the air handling unit's fan has used in order to push the air is going to waste.  .
• 10% of the heating or cooling energy an air handler has put into (or removed from) that air is not getting to its desired destination.  
• 10% of the ventilation air being brought in in the interest of maintaining worker comfort and productivity is not reaching its intended destination

In typical, ducted central air handling systems, all of the energy that the HVAC system uses (hydronic pumps, chillers, boilers, fans, etc.) is used in the interest of altering the temperature of air being served to a space through that ductwork.  In that case, our hypothetical 10% is applied to the entire HVAC system.  HVAC systems are generally either the single largest energy expenditure in office or hospitality facilities or a close second."

 

How?

Gajarsky provided information on how duct testing and sealing takes place: "Testing is performed using specialized diagnostic equipment specifically designed to test duct systems. A calibrated fan is used in conjunction with a pressure gauge that together are tailored to record both pressure and cubic feet per minute (CFM). The heating and cooling equipment are turned off and the duct system is sealed off at all vents. The fan is connected to the return side of the system to measure CFM and a hose is run into a supply vent to monitor pressure within the duct system. The test targets are determined by a calculation using either the heating and cooling equipment size or the square footage of the area served. The fan is used to either pressurize or depressurize the duct system while fan CFM and pressure within the duct system is monitored. Typically systems with large leaks will have low pressure and high CFM readings with tighter systems being the inverse."

 

Gajarsky went on to say: "Sealing is performed by accessing the duct system through drop ceilings and/or attic spaces and applying approved duct sealing materials such as UL-listed 181 foil tape and mastic. The tape is rolled out and stuck onto the leaky joints, and mastic is applied to joints and seams with a brush. Mastic is a glue-like material and is usually the preferred sealing material when a contractor is trying to get the system as leak-free as possible. Ducts systems typically have a trend in leakage locations, which, for the experienced contractor can be identified and repaired quickly."

  

1. Duct testing and sealing improves the efficiency of heating and cooling equipment.
2. Select an experienced and trained contractor with references to perform the work.
3. Testing determines what portion of air fed into the duct will emerge where it is needed.
4. Duct sealing takes place in areas such as joints, seams and penetration points such as screws and damper rods.
5. Ideally perform duct testing and sealing during installation. Work can be performed any time.
6. Ductwork is frequently above drop ceilings.
7. Specialized diagnostic equipment is used to test duct systems.  
8. Sealing materials such as foil tape and mastic are used to seal the leaks.

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