HERS®/Title 24 Clarifications, Differences and RESNET Guidance – FAQs Are there differences in the Energy Pro software used in California for Title 24 compliance vs RESNET Accredited Software Tools? While there is overlap, there are certainly differences. E Pro software cannot be used to produce a HERS® Index and RESNET® Accredited Software cannot be used to show Title 24 compliance. EnergyPro utilizes California’s Alternative Calculation Method (ACM) rules and hourly simulation engines (frequently aligned with or built upon California’s public domain CBECC rules). RESNET tools follow national test protocols (RESNET Publication 002) for calculating standard loads, infiltration, and heating/cooling equipment performance EnergyPro evaluates compliance using California-specific metrics like Time Dependent Valuation (TDV) energy and source energy budgets. RESNET tools score a home using the Energy Rating Index (ERI) / HERS Index, where a reference home scores 100. EnergyPro for Title 24 is approved by the California Energy Commission (CEC) to enforce California’s Building Energy Efficiency Standards (Title 24, Part 6). RESNET tools are governed by the Residential Energy Services Network (RESNET) based on national standards like ANSI/RESNET/ICC Standard 301. [1, 2, 3] What type of infiltration testing is allowed in California? The 2025 Version of Title 24 is mandatory as of 1/1/26. Therefore, now a single-point OR a multi-point blower door test can be performed. The energy model is what the home must be built to. The energy model is created long before construction begins. Multi-point can be used on homes with energy models approved by the AHJ in the Title 24 2025 code cycle (started in 1/1/26). Prior to 1/1/26, ONLY single point testing was performed. Energy models approved under previous code cycles can’t use multi-point. This is an important distinction because homes approved under previous code cycles will continue to be constructed for many years to come, and they are not allowed to use multi-point blower door testing. Can I just model the target infiltration as long as my field measurement beats the target? Raters who have been working under Title 24 may be used to modeling the target and making sure they beat the target. However, for RESNET HERS® Ratings, this practice could only be allowed for Confirmed Threshold ratings. For Confirmed Ratings, the model must reflect the actual test results plus relevant correction factors. In CA, the target is set, and the home must meet it when constructed. If it does not meet it, the energy model can be adjusted with a different target, however it will often cause other requirements (often additional) to be met for the dwelling to be compliant. For example, a blower door target is 3ACH, and the constructed building can’t meet that, then the energy modeler can change it to 4ACH. However, that change may necessitate better windows, a whole house fan, HRV/ERV, etc. It depends on whether the overall energy usage is compliant. How is the single point blower door 10% correction factor applied in California for code purposes? For single point blower door testing, California code targets reflect the “10% in reverse” because when they give a target, it has a +10% printed in it for a single point. For RESNET HERS Rating purposes, the model for a Confirmed Rating must reflect the actual test results plus relevant correction factors. The energy model provides a target. The Rater inputs their result into the CA registry, and it corrects it using a calculation and then penalizes the result by 10%. So the Rater is not certain at the time of testing if the home met the target until it goes through the calculation and penalty. How are California Raters with older manometers handling the conversion from multipoint to single point blower door testing? A lot of California Raters have older manometers because they were required to use single point blower door testing until the end of 2025. Now that they’re doing multi-point blower point testing, some are transitioning to newer models and using the manufacturer’s testing app. For field verifiers still using older manometers, we suggest that they reach out to their manufacturer for multipoint app options that can be used with older manometers. Is a blower door test required in California? CA does not require Raters to do blower doors; they can take a default of 5 ACH. It’s a simple workaround. If you are doing a RESNET® HERS Rating, you are required to perform the blower door test, even for a Confirmed Threshold rating. RESNET guidance is that if you model the default 5 ACH versus the actual test result of 5ACH or less, then you must register the rating as a Confirmed Threshold rating. Regarding ANSI/RESNET/ACCA 310 HVAC Grading and CA Raters who are EPA-certified to do refrigerant charging, can CA Rater’s refrigerant charge be used in place of one of the two approved 310 refrigerant charge methods? The answer is NO. The California process cannot be used in lieu of 310 approved refrigerant charge evaluation methods. Refer to HERS® Standards Chapter 1 – Providers overseeing HVAC Grading. However, it may be recognized in the future if there is a QA process that gives RESNET confidence in it. Is it true that duct leakage targets for Title 24 in CA can be more stringent than ENERGY STAR? Yes With Title 24, the duct leakage targets are based on the condensing unit tonnage; not the square footage of the home. So up to 1000 ft², the CA target is higher than the ENERGY STAR target because it’s based on the tonnage. Above 1000 ft², the CA target is lower than the ENERGY STAR target which is based on CFA. A study was done on this years ago and found that for a strong majority of projects the CA duct leakage targets are more stringent than the ENERGY STAR targets. CA: 20 CFM/1 ton of cooling RESNET® guidance: Title 24 uses a different target. When RESNET becomes an ENERGY STAR HCO in CA, then any ENERGY STAR certified home submitted through RESNET as ENERGY STAR HCO will need to meet both HERS® & ANSI/RESNET/ICC Standards. Does RESNET-accredited software have a high-performance attic input for CA so roof deck insulation and potentially the gable ends (insulated or uninsulated) can be modeled? Yes, RESNET-accredited software programs (such as Ekotrope and REM/Rate) feature robust inputs for modeling High-Performance Attics (HPAs). However, there is a major structural distinction between how national HERS rating software handles this geometry compared to California-specific Title 24 software. [1] What forms are needed to comply with Title 24? Unvented/Sealed Attics (Insulated Roof Deck): If you are moving the thermal boundary to the roof deck, you define the attic space as a separate, unconditioned or semi-conditioned zone. The software allows you to input Roof Deck Insulation (continuous or between-rafter) and its exact R-value Gable End Walls: In a sealed, unvented attic, the gable walls are part of the building’s exterior thermal envelope. RESNET-accredited software allows the input of gable wall areas and insulation types (whether insulated or uninsulated) because they are actively transferring heat to the outside Vented High-Performance Attics: If modeling a traditional vented attic that simply has insulation tacked below the roof deck (a common prescriptive path in California), the software allows you to define a multi-layered ceiling/roof system to accurately capture the performance of both the flat ceiling insulation and the roof deck insulation. However, National RESNET software cannot directly generate or print Title 24 compliance paperwork. To model a high-performance attic for a California building permit, you must use California CEC-approved software like CBECC-Res or Wrightsoft/EnergyPro (which utilize the California Alternative Calculation Method engine) CF1R gets created off the E Pro model and is needed for a building permit. CF2R is a declaration by the trade contractors that they installed the specified energy measures correctly. It is filled out during construction. CF3R is the independent verification signed by a certified HERS® or ECC Rater after they have personally verified and tested the installation
