Code Cycle: 2019 Standards Only!
Reference: 2019 CalCERTS New Construction Training Manual Chapter 6, section 6.
New Form: CF3R-MCH-31
Impact: New 2019 HERS verification
Notes: Verification that whole house airflow meets the target on the CF1R. There are three approved airflow measurement methods, one is new.
RCM188.8.131.52 - Whole-House Fan Ventilation Cooling
A whole-house fan (WHF) is not a mandatory requirement. It is required in some climate
zones when using prescriptive compliance. The three performance compliance options are
1. No WHF is assumed in the performance compliance software (no ventilation cooling).
This will be either energy-neutral, or there will be an energy penalty if the applicable
climate zone assumes the effects of a WHF.
2. A default WHF means this proposed feature is equivalent to the standard feature used to
establish the energy budget of the building (The performance of the fan is de-rated to
account for deficiencies from installing undersized or inefficiently designed WHF).
3. The HERS-verified WHF option allows for modeling the effects of the WHF without
de-rating the system performance. The HERS-verified option also allows modeling a WHF with a higher airflow rate or lower fan efficacy than the default, which improves the
RA184.108.40.206.1 - WHF Airflow Rate Measurement Using Pressure Matching and Fan
Flowmeter. (Option 1)
1. Set up a blower door as you would for a dwelling unit air infiltration test using negative pressure. Cap off the blower door fan. Use one-minute time averaging for pressure and airflow measurements to minimize any wind effects.
2. Open the window(s) that are typically opened during WHF operation.
3. Turn on all WHF’s required to meet the dwelling unit WHF airflow rate. Adjust multiple or variable speed WHF’s to operate at an airflow rate that will be greater than or equal to the rate required for compliance.
4. Adjust the dwelling unit window openings to bring the dwelling unit to the WHF operating pressure (OP) of negative 10 Pa. ±5 Pa. WRT outside.
5. Measure and record the actual dwelling unit depressurization attained (Pa) WRT outside at the WHF-OP.
6. Turn off the WHF and seal the WHF inlet opening(s). The WHF system dampers may be used to seal the WHF inlet opening(s) if the dampers close tightly and will not leak.
7. Do not change the window openings. The same dwelling unit window opening configuration used to establish the WHF-OP shall be used for the BD measurements specified below.
8. Remove the BD fan cover.
9. Increase the BD fan speed to match the WHF-OP measured in step 5.
10. Record the BD airflow, which is also the WHF airflow.
RA220.127.116.11.3 - WHF Airflow Rate Measurement Using Flow Capture Hood (Option 2)
The WHF airflow measurement shall be performed using the following procedures.
1) Open the window(s) that are typically opened during WHF operation.
2) Turn on all WHFs required to meet the dwelling unit WHF airflow rate. Adjust multiple or variable speed WHFs to operate at an airflow rate that will be greater than or equal to the rate required for compliance.
3) Adjust the dwelling unit window openings to bring the dwelling unit to the WHF-OP of negative 10 Pa ± 5 Pa WRT outside.
4) Measure the airflow rate(s) at the inlet grille(s) with a calibrated traditional flow capture hood to
determine the total WHF airflow for the dwelling unit.
No part of the WHF intake shall be blocked or masked off to accommodate an undersized hood.
Operation of the flow hood shall conform to the specifications in the manufacturer's product documentation.
RA18.104.22.168 - WHF Fan Watt Draw Measurement Procedures
When multiple WHF's are used to comply with the required WHF watt draw for the dwelling unit, all WHF's in the dwelling unit shall be operated simultaneously and the sum of the watt draw measurements of the simultaneously operating WHF's for the dwelling shall be determined.
When required for compliance, the WHF watt draw shall be measured using one of the methods used as described in the 2019 Alterations training manual.
- Clamp-on, and
- Utility revenue meter.
RA22.214.171.124 - WHF Compliance Criteria
In order for WHF to comply, the requirements in both subsections (a) and (b) below shall be met.
- The measured WHF airflow (cfm) shall meet or exceed the WHF airflow compliance criterion specified on the CF1R.
- The calculated value for fan efficacy (watts/cfm) shall be less than or equal to the WHF efficacy compliance criterion specified on the CF1R.
The WHF’s used to comply with the Energy Standards must be listed in the Energy Commission’s Appliance Database, which can be accessed at: