When is HERS Verification Required?
When compliance documentation indicates field-testing of specific energy efficiency improvements for Title 24 compliance credit, an approved HERS (Home Energy Rating Systems) certified rater must be used to conduct the field-testing. In California, these raters are part of CHEERS (California Home Energy Efficiency Rating System).
HERS raters are considered special inspectors by building departments.
The HERS provider and rater must be independent from the builder and/or subcontractor installing the energy efficiency improvements to be tested and verified, and can have no financial interest in the installation of the improvements.
HERS Required Verification:
Ducts – Duct Efficiency Improvements that require HERS testing.
q Duct leakage testing – credit if leakage verified to be less than 6% of fan flow.
q ACCA Manual D duct design – credit for the duct layout, engineering calculations and duct system specifications included in the plans. The HERS rater must either diagnostically test the system fan flow and verify that the fan flow specified by the ACCA Manual D design is achieved; or, remove the access panel and verify installation of the (TXV) thermostatic expansion valve.
q Ducts in conditioned space – credit if less than 12 lineal feet of ducts outside the conditioned space.
q Duct surface area – credit for maximum surface area of supply ducts in unconditioned space is 27% (can only be used in conjunction with the ACCA Manual D duct design credit)
q TXV (thermal expansion valve) – used for split system central air conditioners to improve the performance and efficiency of the air conditioner condenser.
Infiltration – Building Envelope Air Sealing requires HERS testing using diagnostic blower door testing.
q Reduced infiltration – requires blower door testing to verify that the target leakage has been achieved. The compliance author using computer “performance” compliance chooses “SLA” for the Housewrap/Air Infiltration credit, and the computer program specifies target CFM at 50 Pascal.
HERS Verification Not Required:
Duct Efficiency Improvements and Building Envelope Air Sealing that do not require HERS testing, only building department inspection:
q Duct insulation – compliance credit available for ducts with insulation greater than R-4.2.
q Radiant barriers – installation of a radiant barrier in the attic increases the duct efficiency by lowering attic summer temperatures.
q Ducts located in crawlspace – credit is available for ducts installed in crawlspaces instead of attics with all of the supply registers located in the floor.
q Building house wrap – credit can be taken for installation of an air-retarding wrap (insulative sheathing and building paper do not qualify as air retarding wraps).
q Multi-Family Housing. The standard design for multi-family housing assumes tight ducts. Credit can be taken for increased duct insulation and sealed ducts only.
q Production Homes. At the builder’s option, HERS testing shall be completed either for each house or for a sample of houses of the same model. In order to take credit using the sample of houses:
o The HERS rater must diagnostically test and field verify the first house of each model.
o To be considered the same model, houses shall be in the same subdivision and have the same energy designs and features, including the same floor area and volume.
o After the initial testing is complete, the builder must identify a group of houses from which a sample will be selected for testing. The group of houses must include those houses expected to be ready for diagnostic testing within a 180-day period.
o The HERS rater must select a minimum of one out of every seven sequentially completed houses in the group. The HERS rater must diagnostically test and field verify the houses selected.
o When a failure is encountered during the sample testing, the HERS rater must conduct re-sampling to assess whether the failure is unique or the rest of the houses are likely to have similar failings.
o When re-sampling reveals a failure, the builder shall: 1) take corrective actions as required in all unoccupied houses in the group and in occupied houses in the group where homeowners have accepted field verification, testing and corrective action; and 2) offer at no charge to homeowners of occupied houses in the group to complete field verification, testing and corrective action if necessary.