Frequently Asked Questions

← Frequently Asked Questions

4. Lowrise Residential Title 24

For starters you must consider a Heat Pump as the source of heating, using electric resistance heat if not going to comply. For the Domestic Hot Water, and electric résistance unit (either tank style or tankless is not going to comply). Try it if you do not believe us, you will need to consider a Heat Pump Water Heater. The good news is that starting with the 2019 code, your Heat Pump heater is compare with a Heat Pump heater in the Standard, same goes for the Heat Pump Water Heater, so any penalty you might have on achieving compliance is related to the design of the rest of the home. See here for further tips.

You can review two sample files we provide, the the lowrise example is the MF Example.bld, we also provide a file  Highrise Res Electric.bld Both are modeled at the Plant level of the tree, Domestic Hot Water tab.  The inputs for the CHPWH are at the bottom section of the input screen, you can choose the type of Heat Pump, quantities, etc, as well as tank volumes, and supplemental loop capacities, tank locations and locations of condensers.  The input at the top is not used in this case if you are doing Lowrise projects.  In the case of Highrise projects the water heater input at the top of the screen is used to supply Nonresidential spaces (corridors, lobbies and support spaces).  No you cannot assign those spaces to the CHPWH, CBECC does not allow for that circumstance, so you will have to assign those spaces to a standalone WH.

When molding HIghrise Res projects, at the PV+Batt tab, we also provide for the circumstance where PV assist is being provided to the Central HPWH, only the top boxes need to be checked, the software will size the PV system for you.  It is important when using this feature that you check you compliance results on the PERF-01, since this PV assist is actually reported there, not onscreen, as a “flexibility” credit, along with the PV size.

When modeling an ADU, there are several circumstances to consider.

In the case of an attached Garage conversion, this is considered an Addition, and the floor space of the Garage is input as New (no it is not an Alteration).  See our example file “Existing+Alterations+Addition.bld” for an example.  Note in this case, the code does allow for the “Existing Wall w/Siding” selection to be used, listed under the wall input.

In the case where they are adding square footage to an existing home, it is treated the same as the Garage conversion, and you may be able to claim the “Wall Extension” selection, also given under the wall input.

In the case of an existing building (garage, shed), not attached to the home, this is also an Addition as described above, and also qualifies for the “Existing Wall w/Siding” provided the siding remains.  Also, any type of Addition to this same structure is still an Addition to the main house.  Existing Floor area, where required, should be for the main house.

In the case of a New building on the site, this is now input as New, and the ADU designation is not relevant.  It is a new home, and will be documented as such, and the output will not indicate ADU.  This circumstance will also require a PV system be installed.

In ALL cases, an ADU will require an IAQ fan, verified in the field by a HERS rater.

At the top level of the Building Tree, in the PV+Batt tab, we offer the option to input a Battery Storage System, however there are some important restrictions on the use of this feature as follows:

  • Battery storage must be fed via a PV system, so you must input an appropriately sized PV system in this same tab.
  • Battery storage and PV are not recognized in the Nonresidential calculations for the purposes of Title 24 Compliance, although it is recognized for Above Code purposes.
  • Battery storage and PV are only recognized for New Construction projects, not for Additions and/or Alterations.

When inputting the Battery system, you will need to indicate the size of the battery, as well as the strategy used to charge the battery.  In most cases this will be the Basic charging selection.  In addition, you will need to indicate the efficiency of the system used to charge the battery as well as to discharge the battery.

These systems are sometimes referred to as Air To Water Heat Pumps.  At the System level of the Building Tree, create a new Central System in the library.  The system type should be set to Hydronic Heat Pump.  Enter the Heating Capacity and COP in the Heating Tab, and the Cooling Capacity and EER in the Cooling Tab.

We have an example of this system in the ResAirToWaterHP.bld example file.

If you wish to make this a ground coupled system (geothermal), at the Plant level of the Building Tree, Hydronic tab, check the box for Ground Coupled.

If the Heat Pump also supplies the Domestic Hot Water, at the Plant level of the Building Tree, Domestic Hot Water tab, create a Heat Pump Water Heater with the COP entered for the Energy Factor.

An unventilated attic (sometimes referred to as a sealed attic) is created in the Assembly Editor by first importing an Attic assembly with R-0 insulation using the green Import button.  At the Res T24 Performance tab, check the box for Unventilated.  Now input whatever level of insulation you have at the rafters under the Below Roof Deck entry.

Note if using this assembly for Prescriptive compliance, the entry in the JA4 tab for Interior Insulation should be included.

When using QII, the CBECC Res engine requires any surfaces (walls, roofs, floors) be selected as different construction assemblies between the existing part of the house or the garage, and the new surfaces.  Thus if you had an R-19 Wall selected for the new part of the home, your Garage and/or Existing part of the home would need to use a different wall, for instance “R-19 Existing” or whatever other unique name you wish to assign.  So you cannot use the exact same assembly names in the library in these cases.

The only time you can consider the ducts as being in conditioned space is if the ducts and air handler are installed underneath the ceiling inside the thermal and air barrier of the envelope.

If the ducts are in an attic with continuous insulation at the roof deck is that considered conditioned space?  No, however, when there is roof deck insulation the attic temperature will be much closer to the conditions within the conditioned space and that is already accounted for in the software. So there is a tremendous benefit from roof deck insulation even if the ducts are not able to be considered as within conditioned space. (NOTE: Because a radiant barrier requires a 1-1/2″ air space, when roof deck insulation is modeled uncheck the radiant barrier option.)

In the Construction Assembly editor at the General tab, we provide a pulldown listing all available Roofing Types that the CEC provides.  The CEC would need to expand that list since we have no control over it, so if you do not see your roofing material, you must choose the closest option provided.

In the Construction Assembly editor, at the Res T24 Performance tab (JA4 tab in older versions), we provide a pulldown listing all Exterior Wall Finishes that the CEC provides.  The CEC would need to expand that list since we have no control over it, so if you do not see your exterior wall material, choose the closest option provided.

Section 150.2 of the code specifically allows small additions that comply Prescriptively to be built with either 2×4 R-15 or 2×6 R-19 walls in cases where that wall is an extension of the existing wall, or the siding is not being removed.  You are responsible for demonstrating that the wall is in fact an extension per this section, or has the siding remaining so we recommend discussing this with the CEC Hotline (800) 772-3300.

Assuming you do meet the exception, we have a pulldown that allows you to indicate that exception at the Wall level of the building tree.  This exception will then be documented on the CF1R.

Select an Attic roof assembly that has the appropriate level of ceiling insulation in the EnergyPro Assembly library.  For a high performance attic with above deck insulation edit the input for “Above Deck Insulation” (or if doing Prescriptive compliance “Exterior Insulation”) and put in an R-Value for the insulation.  For a high performance attic with below deck insulation edit the input for “Below Deck Insulation” (or if doing Prescriptive compliance “Interior Insulation”) and put in an R-Value for the Insulation.

If you do the below deck approach, you should not include a radiant barrier since the insulation will be up against the barrier and will negate the product effectiveness.

In the assembly editor, you will add Exterior Insulation to your wall assembly.  If the project is Nonresidential Performance, this will be done in the Layers tab by clicking on the Yellow Plus sign to add a layer.  Double click on the layer and select an insulation material from the material list, then move it so it is on the exterior of the wall framing.

If the type of project is Prescriptive, then edit the JA4 tab and simply type in the R-Value of the insulation in the Exterior Insulation entry.  If the project is a Residential Title 24 Performance project, enter the Exterior Insulation on the Res T24 Performance tab.

At the top level of the Building Tree, in the Residential tab, you can select from a variety of different ventilation cooling systems, including a Whole House Fan.  Once the type of ventilation cooling system is selected, at the System level of the Building Tree, in the Residential tab, input the total CFM for your fan, along with the total wattage.  A whole house fan will only be recognized on a project that has a ventilated attic, and whole house fans will receive no credit in multi-family occupancies per the CEC guidelines.  Note that the CEC maintains a list of approved whole house fans with specifications on their website.

Select the Assembly Library by clicking on the Libraries in the bottom left corner and selecting the library in the list that appears above.  Now in the right pane, select your roof assembly.  Check the box that indicates the roofing is CRRC-1 certified, then enter your roof reflectance and emittance.  This data will come from your roof properties, typically obtained from the Cool Roof Rating Council website.

Quality Insulation Installation (QII) is indicated at the top level of the Building Tree, in the Residential tab by checking off the box.  Note that while you will get substantial credit for this feature, it is an option you should verify with the builder.

EnergyPro includes the ability to calculate energy design ratings (EDR) as required in the CALGreen energy provisions (Title 24, Part 11) for new construction projects.  Note that this rating will not appear for additions and alterations.  Please review page 2 of the CF1R for more information.  You will find two EDR scores, an EDRe which represents the EDR efficiency of the building alone, and an EDRt, the EDR total efficiency of the building, which includes the savings contributions from Solar PV and batteries.  For the 2019 code, new construction projects are required to comply with both scores.

The EDR is an alternate way to express the energy performance of a home using a scoring system where 100 represents the performance of a building meeting the envelope requirements of the 2006 International Energy Conservation Code (IECC). A score of zero or less represents the energy performance of a building that combines high levels of energy efficiency and/or renewable generation to “zero out” its TDV energy use.

The EDR is similar to the energy rating index in the 2015 IECC. The lower the score, the more efficient the building.

Buildings complying with the current standards are more efficient than the 2006 IECC, so newly constructed buildings will have EDR scores well below 100 (if an EDR were calculated for an older, inefficient home, the score could go above 100).

EnergyPro is “ZNE Ready” meaning it is now configured to allow you to demonstrate a residential building meets the ZNE definition the CEC describes on the CF1R document.  To help you understand this we have provided a new example BLD file designed to run in EnergyPro that shows an Energy Design Rating (EDRt) at Zero.  In addition, the new version provides reporting that will help you and your client understand the energy usage in the home.  Please look at the pages on the sample report, in particular the last two pages.  As an exciting new addition, the software includes a full hourly annual solar system simulation based upon the CECPV/PVWatts simulations.  Look at the example file at the top level of the Building Tree, PV tab.

For residential projects starting in the 2016 code, the standard water heater is a gas fired tank-less water heater in both the Prescriptive and Performance compliance approaches so using any unit with a tank, and especially an electric water heater will produce a significant penalty.

For commercial projects, the standard water heater under Performance is also a gas water heater.  However, under Prescriptive, you are allowed to use an electric water heater.  Our recommendation is to submit the DHW using the NRCC-PLB-01 form which is available under the NR T24 Prescriptive forms list.

Under the Calculation Options, bottom left button, click and you will see the NR T24 Performance calculations in the list above.  Select this, then on the right unclick DHW from the scope and then rerun and the penalty will be gone.

A duplex is treated as single family, as is a townhome or townhouse.  Because the duct leakage requirements for these dwelling units are different from multi-family, they must show compliance based upon each dwelling unit and a model for each unit must be developed, with separate reports.

However, in the case of a townhome that has more than 3 stories, this will fall under the Highrise Residential Standards and a Nonresidential calculation must be run.  In this case a single model can be developed for all of the townhomes.

This would require us to review a detailed set of plans and specifications for the project. Our software support services are confined to issues related to running the software, not how to design a building to be in compliance so this is not something you should contact us about.  However, we do realize the new codes are much tougher so we have compiled some ideas below for you to consider.

In addition, getting a better idea of what the Standard Building looks like so you will understand the budget would be a good idea. There are a lot of online resources to help you understand the energy code including trainings offered by the utilities.  Our support forums also will give you the opportunity to see how other users are getting their buildings to comply.

They are just warnings, if you feel your inputs are set properly then it is fine to ignore them.  EnergyPro sets standards for these inputs and gives you a warning if anything is more than 30% outside of that range.

The CF-1R is required on the plans, we also recommend the Mandatory Measures form.

The amount of credit for an alteration depends on whether a HERS rater verifies the existing conditions. For example, if you are altering existing metal frame, single-pane windows to vinyl frame, low-e windows, if you do not check “HERS Verification” at the top level of the Building Tree, Residential Tab, the software will not prompt you to input the Existing Conditions. You will only input the efficiency of the new windows and your credit is based on the difference between the new window U-factor/SHGC and 0.40/0.35 (values from Table 150.2-B of the Standards). If you check “HERS Verification” and enter the existing conditions of 1.28 U-factor/0.80 SHGC, the credit you receive is based on the difference between these values and the U-factor/SHGC of the new windows.

You can let this default and it will be modeled automatically for you, or you can input the IAQ fan at the Zone level of the tree, Dwelling Units Tab.

A wall facing a garage is input as an interior wall, and thus the program will register no solar gain.

Starting in EnergyPro V7.1, at the System level of the Building Tree, Residential tab, simply check the Wood Stove checkbox.

To model a wood stove or fireplace in older versions, create a new system in the Central System Library. Set the System Type to Split DX, set the Heating Type to Gas Furnace, Central, with an AFUE of 0.78. Zero out the cooling and fans, put ducts in the attic under the Distribution.

For conventional ductless heat pumps (mini-split, multi-split VRF systems) the CEC Compliance Manager simulates these as a system equivalent to the standard minimum efficiency split system A/C with a fully ducted system in the attic, thus affording no credit

When inputting these systems, each INDOOR unit should be input at the System level of the Tree as it’s own System, with a corresponding Zone, thus allowing for the necessary HERS field verification.  You can take compliance credit for theses systems as a VCHP (Variable Capacity Heat Pump) system.  In the case of a VCHP, which requires an indoor unit installed in each habitable room over 150 sqft, we offer the checkbox at the System level of the Building Tree, Residential tab.  Note however that when using this feature, changing the efficiency will not impact the VCHP credit.

You will see the VCHP on the CF1R under HERS Feature Summary, and a new section “Variable capacity heat pump compliance option – HERS Verification” on the CF1R, including a comprehensive list of HERS measures for verification.  Our sample file Res Mini-split demonstrates this feature.

Appendix B of the VCHP staff report is entitled VCHP Compliance Credit—Eligibility Verification Protocols. This document describes the criteria to be met and is available from the newly established CEC website dedicated to VCHP.

There is no set limit to the length of names in the building tree, but CBECC adds data to the field names to keep track of the parent/child relationships and interactions. So you might want to try limiting names to 25 characters.

Only fixed Overhangs and Side Fins are recognized in the modeling tools, the CEC does not currently recognize other devices such as shade screens or blinds.

The calculation engines in EnergyPro that are now used for Title 24 code compliance are developed and maintained by the California Energy Commission. The new Residential and Nonresidential calculation engines they provide are significantly slower than the prior ResSim and DOE-2 engines we provided in older versions of EnergyPro. The new engines incorporate CSE and EnergyPlus, which are more powerful than the older calculations, and simulate the zones much more thoroughly, resulting in longer simulation runtimes.

Try to keep the number of zones in your model to an absolute minimum, but it is not unusual to see run times of over an hour on more complex models.

To speed up run times, you can select the Quick Analysis option, which will run a partial year simulation.  In the bottom left, click on the Calculations.  In the list that appears above, select either Res T24 Performance or NR T24 Performance.  On the right will appear the option for Quick Analysis.  This will cut your runtime in half.  However that option will trigger a report that includes a watermark that states “Not useable for compliance” since you must run the full year for code compliance.

Another option is to check the box for “Do Not Generate PRF01/CF1R”  This will skip the report generation feature that occurs at the end and can save additional time, but you will not get the Title 24 reports needed for permitting.

This check box is to enable modeling the exception for zonally controlled systems with a bypass duct to only meet 150 CFM/ton. The 150 CFM/ton (an energy penalty) does not have to be verified by a HERS Rater, however any level higher than 150 CFM/ton for a zoned system and any if you want to include a bypass duct and not meet 350 CFM/ton.

To model a Gas Boiler with Radiant Floor Heating, start at the Central System Library.

At the Heating Tab:

System Type: Split DX

Heat Type: Hot Water   (Will use efficiency from boiler)

Heating Output: Output of System

Cooling tab: enter relative cooling information, or Zero for output if there is no cooling (See the topic on No Cooling)

Fans Tab: 0 cfm, 0 hp

At the System Level of the Building Tree:

General Tab:

Select the Central System entry created above.

Hydronic Space Heating: Choose DHW or Boiler provide heat. Note this will point the program to either the DHW or the Heating Hot Water tab at the Plant level of the tree for the source of heat.

Distribution Tab:

Heating Distribution: Radiant Floor

Select a heated slab-on-grade from the library at the Slab element.


If the same boiler is used for radiant floors and domestic hot water, model the boiler in the DHW tab and at the System level of the tree select ‘DHW boiler provides heat’.

Sample file located in My Documents\EnergyPro x\Projects\Low-rise Combined Hydronic.bld

It may be the case that there is a dedicated boiler for radiant heat. In this case, model that boiler in the Boiler tab and in the Residential tab select ‘Heating boiler provides heat’. Then model the Domestic hot water (used for sinks, showers) in the DHW tab.

A sample file is located in My Documents\EnergyPro X\Projects\Lowrise Res Separate DHW & Hydro.bld

Below is a list of tabs in which you need to enter information for a residential title 24 calculation. You will not need to enter every available input in each tab.

Building icon:

Building Icon


Project Design Data, Project Title, Designer

Plant Icon:

Plant Icon


Heating Hot Water (if you have a boiler for space heating which is separate from the domestic hot water heater), Domestic Hot Water

System Icon:

System Icon

General, Distribution, Residential, Hers Credits (if you are taking HERS Credits)

Zone Icon:

Zone Icon


Room Icon:

Room Icon


Within the Room icon, you will enter building assemblies such as Roofs, Walls and floors by right clicking on the room icon and selecting Add / …

You do not need to model lighting in a residential title 24 calculation.

In the Central System Library, create a new system. Set the System Type to SplitDX. Now, set the heating type to Electric, and input the HSPF as 3.413

Prescriptive measures are the values of the standard package A in that climate zone – it is also the design of the baseline building; mandatory measures have to be meet no matter what. For example if a building may comply using the performance approach, with only R-7 insulation in a raised floor, but R-19 must be installed because that is the mandatory minimum.

Interior surfaces are surfaces between two spaces and can be either walls, ceilings or floors.  Note that interior walls can also contain doors.  If you have an interior window, treat it as an interior door in an interior wall.  Insert an interior surface in the room and set it adjacent to the other room.  If you do not set it adjacent to another room, or you set it adjacent to itself, it is treated as adiabatic.

In New Construction Homes, Title 24 recognizes (and generally requires in order to comply) your inputs for PV, however in no case does the credit get recognized in additions and alterations.

In Nonresidential occupancies, Title 24 does not allow you to take credit towards compliance.  In the remaining performance calculations, EnergyPro will assign full benefit for the PV production.

EnergyPro offers three possible scenarios here for modeling this type of device as follows:

Nonresidential Calculations that use ducted HVAC systems in EnergyPro that are not Zonal (FPFC, PTAC, WSHP, VRF) have Exhaust Air Heat Recovery ERV or Heat Recovery Ventilator HRV as an option on the HVAC system.  See the Outside Air tab in the Central System Library for these input options.

Nonresidential Calculations can also specify at the Zone level of the Building Tree, Mechanical tab, the use of a Balanced Ventilation system with the option of energy recovery.  This is a new option in EnergyPro 8, and would typically apply to an ERV or HRV in a highrise residential application.

Lowrise residential buildings have the option also.  Start by going to the Top level of the Building Tree, Residential tab and specifying a non-default IAQ fan.  Now at the Zone level of the Building Tree, Dwelling Units tab you can configure the IAQ fan as a balanced ventilation system with the option of specifying the heat recovery effectiveness.

For Title-24 compliance purposes, the CEC requires cooling to be included in the proposed building model.  When modeling a low-rise residential project, the software will include a default cooling system when calculating the results.  This system is defined automatically and you have no option to change the definition of the system.  When modeling a nonresidential project, you are responsible to define the default cooling system for your project, you cannot leave it undefined.  This would be a code minimum efficiency cooling system included as part of your model.

If you find your cooling numbers are causing the building not to comply, review your window inputs and in particular the SHGC since that will affect the cooling usage of the default system.

No, the standard building is a fixed entity based upon Title 24 guidelines, and the CEC does not permit you to change this.  To see the building comparison that Title 24 uses in the standard design, look at the Residential and Nonresidential Alternative Calculation Method Manuals.

You probably have a wall, roof or floor selected that has a name which does not match the actual R value of the assembly.  See screenshot below.  You can name a wall anything you want.  The actual R value that will be used in the calculation and will show up on the report is highlighted in the screenshot.  You will need to select a different assembly with the proper R value.


Building ASssembly R Value

Because the PRF-01 and CF-1R reports are created through an online based report generator on the CEC website, you will have to have an Internet connection in order to generate any Certificates of Compliance. Assuming you have Internet, you might check with your IT department to see if your system blocks the report generator from being accessed. You also have the option of turning off the reports, this option is found by clicking on the bottom left “Calculations” and then in the list above selecting the appropriate calculation.  The display on the right will show the option to turn off the reports. You will eventually have to uncheck tis option and rerun the calculations to get the final Certificate of Compliance.

Yes, since all single family buildings regardless of number of stories are considered low-rise residential, you can use do this (the three-story limit does not apply to Occupancy Group R-3). Note however that the CEC CBECC Res engine is limited to 3 stories so you will just have to trick it and input the building as though it were 3 stories.

If you select the Calculation option on the bottom left side of the screen, then select the T24 Performance calculation (either Res or NR) in the list that appears above this selection, you will see an option to “View CBECC Log”. If you click on this button, you will see the CEC log file reporting the results of the simulation. Note that this file will not exist unless you first uncheck the option for “Delete Temporary Files”, then click on calculate to run the simulation. At the end of the simulation you can view this log file and see what problems you have.

← Frequently Asked Questions

Comments are closed