RA3.7 contains procedures for verification of heat recovery efficiency and fan efficacy, and for measuring the airflow rate for mechanical ventilation systems.
RA3.7 is applicable to mechanical ventilation systems in residential dwelling units.
RA3.7 provides required procedures for installers, HERS raters and others who are required to perform field verification of mechanical ventilation systems for compliance with Part 6.
| Diagnostic | Description | Procedure |
| Whole-Building Mechanical Ventilation Airflow | Verification of whole-building ventilation system airflow rate . Continuous Operation | RA3.7.4.1 |
| Whole-Building Mechanical Ventilation Airflow | Verification of whole-building ventilation system airflow rate . Intermittent Operation | RA3.7.4.2 |
| Kitchen Local Mechanical Exhaust | Verification of vented range hood airflow rate or capture efficiency | RA3.7.4.3 |
| Heat Recovery Ventilation (HRV) or Energy Recovery Ventilation (ERV) Rated Performance Verification | Verification of the HRV/ERV fan efficacy (W/cfm) or heat recovery efficiency. | RA3.7.4.4 |
The instrumentation for the air distribution diagnostic measurements shall conform to the following specifications:
All pressure measurements shall be measured with measurement systems (i.e., sensor plus data acquisition system) having an accuracy equal to or better than ± 1% of pressure reading or ± 0.2 Pa (0.0008 inches water) (whichever is greater). All pressure measurements within the duct system shall be made with static pressure probes such as Dwyer A303 or equivalent.
All measurements of ventilation fan airflow rate shall be made with an airflow rate measurement apparatus (i.e., sensor plus data acquisition system) having an accuracy equal to or better than ± 10% of reading. The apparatus shall have an accuracy specification that is applicable to the airflow rates that must be verified utilizing the procedures in Section RA3.7.4. Airflows shall be measured at the mechanical ventilation fan’s inlet terminals/grilles or outlet terminals/grilles.
All instrumentation used for mechanical ventilation system airflow rate diagnostic measurements shall be calibrated according to the manufacturer’s calibration procedure to ensure the airflow measurement apparatus conforms to the accuracy requirement specified in Section RA3.7.2.2.
Ventilation system airflow rate shall be measured using one of the apparatuses listed in Section RA3.7.3. The apparatus shall produce airflow rate measurements that conform to the accuracy requirements specified in Section RA3.7.2 for measurements of residential mechanical ventilation system airflow at system inlet or outlet terminals, grilles, or registers for single or multiple branch ventilation duct systems.
The airflow rate measurement apparatus manufacturers shall publish in their product documentation, specifications for how their airflow measurement apparatuses are to be used for accurately measuring residential mechanical ventilation system airflow at system inlet or outlet terminals, grilles or registers of single or multiple branch ventilation systems.
The airflow measurement apparatus manufacturers shall certify to the Energy Commission that use of the apparatus in accordance with the specifications given in the manufacturer's product documentation will produce measurement results that are within the accuracy required by Section RA3.7.2.2.
For the airflow measurement apparatuses that are certified to the Commission as meeting the accuracy required by Section RA3.7.2.2, the following information shall be posted on the Energy Commission website, making the information available to all people involved in the airflow verification compliance process:
-
The product manufacturers' model numbers for the airflow measurement apparatuses.
-
The product manufacturers' product documentation that gives the specifications for use of the airflow measurement apparatuses to accurately measure residential mechanical ventilation system airflow at system inlet or outlet terminals, grilles or registers of single or multiple branch ventilation systems.
A manufacturer's certification to the Commission of the accuracy of the airflow measurement apparatus, and submittal to the Commission of the product documentation that specifies the proper use of the airflow measurement apparatus to produce accurate airflow rate measurements shall be prerequisites for allowing the manufacturer's airflow measurement apparatus to be used for conducting the system airflow verification procedures in Section RA3.7 for demonstrating compliance with Part 6.
A flowmeter designed for measurement of residential exhaust airflows that meets the applicable instrument accuracy specifications in RA3.7.2 may be used to measure the mechanical exhaust ventilation airflow.
A powered and pressure balanced flow capture hood (subsequently referred to as a Powered Flow Hood3) that has the capability to balance the flow capture static pressure difference between the room and the flow capture hood enclosure to 0.0 ± 0.2 Pa (0.0008 inches water) and meets the applicable instrumentation specifications in Section RA3.7.2 may be used to verify the ventilation airflow rate if the powered flow hood has a flow capture area at least as large as the ventilation system inlet or outlet, terminal, register, or grille in all dimensions. The fan adjustment needed to balance the flow capture static pressure difference between the room and the flow capture hood enclosure to 0.0 ± 0.2 Pa (0.0008 inches water) shall be provided by either an automatic control or a manual control operated in accordance with the apparatus manufacturer's instructions specified in the manufacturer's product documentation.
A traditional flow capture hood4 meeting the applicable instrumentation specifications in Section RA3.7.2 may be used to verify the ventilation system airflow rate if the non-powered flow hood has a capture area at least as large as the ventilation system inlet or outlet terminal, register or grille in all dimensions.
This section describes the procedures used to verify Mechanical ventilation system airflow.
If multiple fans are specified to operate simultaneously to provide the total required ventilation airflow, the measurements shall be made with all applicable fans operating simultaneously.
- A flow measuring device that meets the applicable instrumentation requirements given in Section RA3.7.2, and RA3.7.3 shall be used to measure the ventilation airflow(s).
- Measure and record the ventilation airflow(s).
- If the measured total airflow is greater than or equal to the ventilation airflow rate required by the Standards or the Certificate of Compliance, the mechanical ventilation system complies. Otherwise the mechanical ventilation system does not comply, and corrective action shall be taken.
-
Confirm that both the supply side and the exhaust side of the balanced system operate simultaneously in response to a shared system control.
-
Measure the airflow rate for the exhaust side of the system.
-
Measure the airflow rate for the supply side of the system.
-
Calculate the percent difference between the exhaust and supply airflow rates.
-
Calculate the average of the exhaust and the supply airflow rates.
-
If the exhaust and supply airflow rates are within 20% of each other, and the average of the exhaust and supply airflow rates is greater than or equal to the airflow rate required by the Standards or the Certificate of Compliance, the balanced ventilation system complies. Otherwise, the system does not comply, and corrective action shall be taken.
-
If the balanced system is an HRV or ERV and compliance with a recovery efficiency or fan efficacy specification is required, then also perform the verification specified in RA3.7.4.4.
The Executive Director may approve intermittent mechanical ventilation systems, devices, or controls for use for compliance with field verification and diagnostic testing requirements for mechanical ventilation airflow, subject to a manufacturer providing sufficient evidence to the Executive Director that the installed mechanical ventilation systems, devices, or controls will provide at least the minimum ventilation airflow required by the Standards, and subject to consideration of the manufacturer's proposed field verification and diagnostic test protocol for the ventilation system(s). Ventilation airflow of systems with multiple operating modes shall be tested in all modes designed to comply with the required ventilation airflows.
Approved systems, devices, or controls, and field verification and diagnostic test protocols for intermittent mechanical ventilation systems shall be listed in directories published by the Energy Commission.
The verification shall utilize certified performance rating data from the Home Ventilating Institute (HVI) Certified Home Ventilating Products Directory at https://hvi.org/proddirectory/index.cfm, the Association of Home Appliance Manufacturers (AHAM) Certified Products Directory at https://www.aham.org/AHAM/What_We_Do/Kitchen_Range_Hood_Certification, or another directory of certified product performance ratings approved by the Energy Commission for determining compliance. The verification procedure shall consist of visual inspection of the installed kitchen range hood to verify and record the following information:
- The manufacturer name and model number.
- The model is listed in the HVI, AHAM, or other CEC-approved directory.
- The rated airflow value or rated capture efficiency value listed in the HVI, AHAM, or other CEC-approved directory.
- The sound rating value listed in the HVI, AHAM, or other CEC-approved directory.
- If the value for the rated airflow or rated capture efficiency given in the directory is greater than or equal to the airflow or capture efficiency requirements specified in the Standards, and if the value for the sone rating given in the directory is less than or equal to the sone rating requirements specified in Standards, then the kitchen range hood complies. Otherwise the kitchen range hood does not comply. If the kitchen range hood is not listed in the HVI, AHAM, or other CEC-approved directory, then the system does not comply.
The verification shall utilize certified performance rating data from the Home Ventilating Institute (HVI) Certified Home Ventilating Products Directory at https://hvi.org/proddirectory/index.cfm, or another directory of certified product performance ratings approved by the Energy Commission for determining compliance. The verification procedure shall consist of visual inspection of the installed system to verify and record the following information:
-
If compliance with a fan efficacy performance rating (w/cfm) is required, then determine and record the fan efficacy rating for the installed model using the model details in the energy ratings in the HVI, or other CEC-approved directory in accordance with steps a, b, and c below.
-
From the energy ratings in the HVI or other CEC approved directory, determine, and record the rated Power Consumed (Watts) at 32 degrees Fahrenheit, at the closest Net Airflow (cfm) listed in the directory that is greater than or equal to the ventilation airflow (cfm) required on the certificate of compliance. Alternatively, linear interpolation of the directory ratings at 32 degrees Fahrenheit shall be allowed if the interpolated value is calculated based on a Net Airflow (cfm) that is equal to the ventilation airflow (cfm) required on the certificate of compliance. Interpolation shall be in accordance with equation RA3.7-1. Extrapolation of the directory ratings at 32 degrees Fahrenheit shall not be allowed.
Equation RA3.7-1
pc = pc1 + [(na – na1) / (na2 – na1)] X (pc2 – pc1)
where:
na is the known value for Net Airflow equal to the ventilation airflow required on the certificate of compliance,
pc is the unknown value for Power Consumed (Watts) at 32 degrees Fahrenheit.
na1 and pc1 are the closest rated values at 32 degrees Fahrenheit for Net Airflow (cfm) and Power Consumed (Watts) respectively that are below the known na value. na2 and pc2 are the closest rated values at 32 degrees Fahrenheit for Net Airflow (cfm) and Power Consumed (Watts) respectively that are above the known na value -
Divide the value for Power Consumed (Watts) recorded in step b, by the Net Airflow (cfm) used in step b to determine the Power Consumed.
-
-
If compliance with a sensible recovery efficiency (SRE) performance rating (%) is required, then determine and record the SRE rating for the installed model using the model details in the energy ratings in the HVI or other CEC-approved directory in accordance with steps a, and b below.
-
Record the required ventilation airflow (cfm) for the installed HRV/ERV as specified on the certificate of compliance.
-
From the energy ratings in the HVI or other CEC approved directory, determine, and record the rated SRE (%) at 32 degrees Fahrenheit, at the closest Net Airflow (cfm) listed in the directory that is greater than or equal to the ventilation airflow (cfm) required on the certificate of compliance. Alternatively, linear interpolation of the directory ratings at 32 degrees Fahrenheit shall be allowed if the interpolated value is calculated based on a Net Airflow (cfm) that is equal to the ventilation airflow (cfm) required on the certificate of compliance. Interpolation shall be in accordance with equation RA3.7-2. Extrapolation of the directory ratings at 32 degrees Fahrenheit shall not be allowed.
Equation RA3.7-2
sre = sre1 + [(na – na1) / (na2 – na1)] X (sre2 – sre1)
where:
na is the known value for Net Airflow equal to the ventilation airflow required on the certificate of compliance,
sre is the unknown value for SRE at 32 degrees Fahrenheit.
na1 and sre1 are the closest rated values at 32 degrees Fahrenheit for Net Airflow (cfm) and SRE respectively that are below the known na value.
na2 and sre2 are the closest rated values at 32 degrees Fahrenheit for Net Airflow (cfm) and SRE respectively that are above the known na value.
-
-
Determining Compliance.
-
If the value determined for SRE by one or both of the alternatives in step 4 for the installed system is greater than or equal to the SRE required for compliance, then the system complies with the sensible recovery efficiency rating requirement. Otherwise the system does not comply.
-
If the value determined for fan efficacy (W/cfm) by one or both of the alternatives in step 3 for the installed system is less than or equal to the fan efficacy required for compliance, then the system complies with the fan efficacy rating requirement. Otherwise, the system does not comply.
-
If compliance with both fan efficacy and sensible recovery efficiency ratings are required, then both ratings shall comply at the same Net Airflow (cfm), otherwise the system does not comply.
-
If the system is not listed in the HVI or other CEC-approved directory, then the system does not comply.
-
3 Also known as "active" flow hood, or "fan assisted" flow hood.
4 Also known as “non-powered flow hood, "standard" flow hood, "commercially available" flow hood, or "passive" flow hood.