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• If whole house fan product has a ducted system, ensure the duct is installed per
manufacturer instructions for the whole house fan. Improper installation may cause HERS
test failure.
• If whole house fan system has damper doors, ensure dampers are opening/closing as
expected. Malfunctioning damper doors may produce HERS test failures.
• If whole house fan is a multi-speed system, verify that you are testing at the lowest speed
required to meet the minimum WHF airflow rate listed on CF-1R report. Title 24 reports that
have modeled medium speeds for 2019 code, only need to be tested at medium speed.
• If the measured flow rate is failing (too low) try running WHF at a higher speed.
• If the measured airflow rate is failing HERS test at its highest operating speed, check the
attic pressure with reference to the home. Attic pressure WRT the home should be less than
40 Pa. Higher readings may indicate the home may not have enough venting for the installed
WHF.
• If the whole house fan is moving high volumes of air and you are unable to zero out the
hood, adjust the stand to be closer to the bottom of the flow hood. Aim for about 1’ away.
