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CHEERS/HERS Raters - HVAC Duct Testing

California Home Energy Efficiency Rating System, Inc. (CHEERS) is a California Statewide non-profit organization dedicated to promoting energy efficiency. CHEERS was created to provide a simple, accurate and reliable method of measuring the existing energy efficiency of a home, estimate the annual costs of the existing home and provide a list of energy saving recommendations for improvements.

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HERS Rating

The California Energy Commission is required by Public Resources Code Section 25942 to establish regulations for a Home Energy Rating System (HERS) Program to certify home energy rating services in California. The goal of the program is to provide reliable information to differentiate the energy efficiency levels among California homes and to guide investment in cost-effective home energy efficiency measures.

The California HERS Program includes field verification and diagnostic testing available through Commission-certified providers and their raters when duct efficiency, thermostatic expansion valves (TXVs), refrigerant charge and airflow measurement, and building envelope sealing measures are used for complying with the new 2001 building efficiency standards (effective June 1, 2001).

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Duct Leakage Testing

Duct leakage measurements are used to diagnose duct leakage problems, estimate energy loss from duct leaks, and verify the quality of duct system installation. Energy professionals can use duct testing equipment or a blower door to determine how leaky, or energy-inefficient, a duct system is.

Duct leaks can make your home uncomfortable and unhealthy. Leaky return ducts can pull pollutants into your home from your attic, crawl space, basement or garage. Poorly installed supply ducts can cause dangerous backdrafting of fireplaces, wood stoves, and naturally vented gas and oil furnaces and water heaters. Leaky ducts also create pressure differentials in the house that cause drafts and moisture problems.

A poorly installed duct system costs you money, too. It reduces the efficiency of a forced-air furnace, heat pump or air conditioning system by 20 percent to 40 percent.

What are Performance Tested Comfort Systems?

Most contractors don’t test the performance of the heating and cooling systems they install. Performance Tested Comfort Systems are tested for efficient operation and safety. Because ducts are sealed, drafts are reduced and more of the heating or cooling produced by the furnace, heat pump or air conditioning system is delivered to the rooms you live in. Performance Tested Comfort Systems certified contractors also conduct tests and make any necessary repairs to ensure the furnace doesn’t depressurize the house and cause backdrafting of combustion appliances.

How does duct testing and sealing make my home healthier?

Duct testing and sealing reduces indoor air pollutants two ways:

First, testing duct systems for pressure balance can uncover negative indoor air pressures that cause the whole house to leak (bringing in air from the attic, crawl space, basement or garage) and cause backdrafting of fireplaces, wood stoves, furnaces and water heaters. Without testing, many of these problems are not uncovered and corrected.

Second, sealing leaks in return ducts stops pollutants from being drawn into the home from the attic (insulation fibers, dust), crawl space (moisture, radon gas, pesticides, mold and mildew spores, animal residue, insulation fibers, dust), basement (mold, mildew, dust, carbon monoxide, chemical fumes) and the garage (car exhaust, carbon monoxide, chemical fumes, dust).

Don’t try to fix your ducts without advice
from a professional. If you seal them
improperly, you may make the problems
worse and create health risks.

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Frequently Asked Questions

Will I save on my energy bills?
Problem ducts make your heating and cooling system work longer and harder to keep you comfortable. Sealing leaky ducts improves the efficiency and performance of your heating and cooling system. Many homeowners who had their ducts tested and sealed have noticed a decrease in their monthly energy bills and an increase in comfort.

How long will it take to test and repair my duct system?
It depends on the size of the system, accessibility to the ductwork and duct materials used. Typically, duct testing takes just one to two hours. Repair time ranges from a couple of hours to several days.

What is a Performance Tested Comfort Systems certified contractor?
Certified contractors receive extensive classroom and in-field training. They learn how to use high-tech testing equipment to identify duct leakage, house depressurization and combustion appliance problems. And they learn how to safely and effectively repair and seal duct systems. Before they are certified as a Performance Tested Comfort Systems contractor, they must pass a written exam and demonstrate proper testing and sealing techniques in the field.

Should I test my home for duct problems?
Your home is a candidate for duct sealing if you have a furnace, heat pump or air conditioning system and ductwork runs through the attic, garage, crawl space or unheated basement. Any one of these problems may be a sign of leaky ductwork:

  • Parts of your home are uncomfortably hot or cold in summer or winter
  • Your heating or cooling bills seem too high
  • Your feel a draft at heating registers when the heat is off
  • Your home has a musty odor

What’s the first step?
Call a Performance Tested Comfort Systems certified contractor to evaluate your duct system. At the end of the test, you will know:

  • If your duct system is leaky and needs repair
  • If your home has adequate ventilation
  • The potential for backdrafting problems in your home
  • The estimated cost to properly seal your duct system

What are the most important elements of an efficient HVAC and duct system?

A. There are four elements: 

  • The duct system must have a good design that is planned early in the construction process and understood by the builder, framer, structural engineer and truss company. Every fit and bend in the duct system affects the efficiency of the system.
  • The system must be properly installed with the correct amount of airflow and refrigerant verified through the tests listed in the appendix of the ACM.
  • The system must be appropriately sized according to Air Conditioning Contractors of America standards.
  • There must be easy access to the coil for maintenance.

What are "sealed ducts"?
Ducts are tubes that make up a system to distribute heated or cooled air to various rooms throughout a house. Sealed ducts have appropriately installed joints and connections to minimize leakage of conditioned air. Air leakage cannot be seen by the naked eye, therefore, diagnostic testing verifies leakage and, by using complying tapes, mastics and mechanical fasteners or aerosol sealant, leaks can be closed.

What is a "Duct Blaster®"?
A Duct Blaster® is a tool used to test the air leakage rate of forced air duct systems. The equipment and appurtenances consist of a calibrated fan, pressure tape to temporarily seal all the registers and grilles, flexible duct to fasten the system to the central return or the air handler cabinet of the duct system; and a digital monometer to measure fan flow and duct pressure.

Duct leakage is measured by either pressurizing or depressurizing the duct system and precisely measuring the fan flow and duct pressure. Duct leakage measurements are used to diagnose and demonstrate leakage problems, estimate efficiency losses from duct leakage, and certify the quality of duct system installation.

Do all houses have to have their duct systems sealed?
Not necessarily. It depends on the compliance approach. Under the Title 24 Prescriptive Compliance Method ducts must be sealed in all climate zones. Under the Performance Compliance Method, the builder may make credit by "trading-off" between the envelope, water heating and space conditioning, but will probably find that duct sealing is the most cost-effective measure.

Can I still put an HVAC forced air unit on a platform in the garage?
Yes. The return plenum that is normally located under the platform must contain either a duct to the HVAC unit or be constructed of sealed sheet metal or ductboard, not the commonly used sheetrock or drywall.

What kind of duct tape can I use?
You must use a UL 181 approved tape or sealant. Duct tape, which is a cloth-backed tape with rubber adhesive is not permitted in the new Title 24 unless it is used with mastic and a draw band.

What are the new AB970 mandatory requirements for duct systems?
The requirements under AB970 include:

  • UL 181 approved tapes and sealants.
  • No cloth-backed rubber adhesive tapes without mastic and a draw band.
  • Building cavities cannot convey conditioned air.
  • Plenum insulation must have a R4.2 resistance factor.
  • Ducts must be supported every four inches to reduce sagging.

In addition, when using the Prescriptive Compliance Approach, every custom home and every seventh production home must be tested by a HERS rater. In many cooling load zones, a thermostatic expansion valve (TXV) is required to meter the correct amount of refrigerant in a system.

What is a "HERS" rater?
A HERS rater is an energy expert certified by the California Energy Commission (CEC) to rate homes in California according to the Home Energy Rating System (HERS). These services include field verification and diagnostic testing to differentiate energy efficiency levels among homes tested for duct efficiency and envelope leakage for compliance with current building efficiency standards. You can locate a HERS rater at

What do I have to do to be a HERS rater?
To become a HERS rater, you must take a certification exam and become certified by CHEERS. To do this you can take a training program through CHEERS that provides technical instruction on the rating procedures and background on residential construction and home heating and cooling equipment.

What is CHEERS?
The California Home Energy Efficiency Rating System or CHEERS, is a non-profit educational organization that trains and provides services to HERS raters. CHEERS has been approved by the California Energy Commission as a "Provider" for HERS.

CHEERS also provides information to consumers and builders on energy efficiency and provides a listing service to find a HERS rater who can measure the energy efficiency of a home. You can learn more about CHEERS by visiting or calling, 1-800-4-CHEERS.

Do I need to seal the ducts in multi-family housing?
Yes, if the Prescriptive Compliance Method is used, the ducts must be sealed according to the minimum requirements described above. Open-ended fan coils may not be used in a sheet rock plenum unless the plenum is lined with sealed ductboard or sheet metal. See Chapter 4 of the California Energy Commission's Residential Manual for details on duct testing and sealing.>

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