A duct leakage HERS test is a pressure test to measure any air loss in your duct system. The HERS Rater seals off the duct system to pressurize it and uses special duct-testing equipment that measures the input and loss. The Energy Department found that the average homes duct system leaks approximately 30% and made duct leakage testing mandatory in October of 2005.
A Home Energy Rating System Rater (HERS Rater) is a person trained and certified by a state-approved organization through the California Department of Energy to perform testing pertaining to conserving energy. HERS Raters can perform many services, from duct testing to builder inspections for LEED or Energy Star Programs. They can also do energy credits and other energy-saving inspections.
Even if you only changed out the condenser you need a duct leakage test. As of October of 2005, changing or adding the coil, condenser, or furnace or adding more than 40 feet of ducting needs a HERS Duct Leakage Test. The city requires the CF-6R and CF-4R forms before finalizing the permit. Effective January 1, 2010 the DOE added a refrigerant charge measurement. We can provide you with both of these forms after the HERS Rating is completed.
The Heating/Ventilation/Air Conditioning System, otherwise known as HVAC, is the biggest consumer of energy in a home. Ductwork is designed to deliver the conditioned air through floor or ceiling vents known as supplies. All HVAC systems have returns designed to remove untreated air from any room while simultaneously supplying newly treated air. Both directions of air flow, into and out of each room, is contained and insulated in ducts. When ducts have leaks in them, the conditioned air is allowed to escape, literally blowing your money out the door.
Each HVAC system has a central component where the air is handled and negative airflow, known as suction, is converted into positive air flow, known as blowing. If there exists a leak on the supply side of your ducts, the conditioned air begins to leak into otherwise unoccupied areas such as your attic. If there exists a leak on the return side of the ducts, it means that air from unconditioned spaces are mixing with the conditioned air, not only increasing costs but placing your health at risk.
There are four manners through which passing results can be obtained, and three that handle the actual calculated air flor and leakage within your CFM.
They are as follows:
- 15% of calculated airflow will leak with 400 CFM per ton formula.
- 60% reduction to the initial leakage, before change-out, can be achieved.
- The leakage outside can be measured to ensure it is less than 10%. This requires a blower door and all duct supplies must be taped off.
- If one of the aforementioned passing methods is not achieved, passing results can still be obtained if the contractor seals the visual leaks, something visually verified with smoke by a HERS rater.
You must visit one of two places: the furnace or the condenser.
If you are looking at the condenser you must find the model number and with that, there will be a number that will yield the size of your unit in tons, when divided by twelve. Calculations for this are performed with 400 CFM per ton. For example: a 4.5 ton unit will have 1800 CFM.
Another calculation is air load, derived from the output BTU’s of the furnace. If the output BTU’s are specified on the model number as, for example, 89,000 one would multiple 89 by 21.7 to achieve 1931. Because you want the home to be guaranteed within the passing zone, the smaller of the two numbers is used to calculate the target leakage in terms of CFM.
In order to calculate target leakage, you multiple the total air load by the amount of leakage allowed for change-outs. Using the example above, the total air load is 1800 and the allotted leakage is 15% which results in 270. After this all supply registers are sealed and the duct system is pressurized with a duct blaster. Sensors can be attached to the duct system and the blaster can be channeled from there using a manometer, which measures static pressure. The system is then pressurized to 25 Pascal (which is the standard amount of air pressure in a duct system operating at full capacity) and the manometer will read the air leakage in CFM.
For newly installed duct systems, the allotted leakage is 6%. For new construction the leakage allotted is 4% if tested at rough-in and 6% when tested for final. For alterations and change-outs please refer to question 3.
Building codes state that each building owner or agent has the option of hiring a 3rd party to perform verification on their building or home, or they can opt to choose to be part of a sample wherein the contractor creates groups of no more than 7 jobs where duct sealing was required and a HERS rater will select one out of that group to test at random; should the random sample pass, then all others in that group pass as well but if the random sample fails, then the first home is revisited and retested until it passes. If the second test also fails, the entire sample group must be tested 100%.
A calibrated manometer is used with a duct blaster.
The length of time required is contingent upon the size of the building or home, but typically the time ranges between 30 minutes and 2 hours.
You have the option of installing an EER 12 with a refrigerant charge measurement or with TXV, with 0.82 or 0.92 AFUE as well as increased duct insulation.
This is an option for every building owner. If they opt to be included in a sample, they must be notified and must be informed of their alternative option to instead have 100% testing conducted.
Having a home or building 100% tested is the only manner by which to guarantee compliance with all California State requirements and to minimize leakage. Properly functioning HVAC systems benefit homeowners and building owners in a plethora of ways including saving money, creating a healthier living environment, conserving fuels, and protecting the atmosphere.
The average home in California has more than 30% of air flow leaking from just the ducts.