Title 24 FAQs

Have you got a question that isn't covered in the FAQs below? Contact our Title 24 team for more information.

What software should I download to perform Title 24-2013 and Title 24-2016 Compliance?

Two downloads are required, depending on the compliance version: ‘IESVE for Engineers’ [http://www.iesve.com/software/download/ve-for-engineers] and ‘CBECC-Com’ [http://bees.archenergy.com/software.html].

After the installation, open the software and request license keys. When the license is activated, you’ll have a free 30-day trial.

Can I use IESVE software for the CEA Exam, as organized by CABEC?

Yes.  Please ensure you have IESVE installed on your laptop, with a valid license, before attending the exam location.

How much does IESVE software for Title 24 Compliance cost and how do I purchase it?

Pricing is below. Please request an annual license by contacting Title24@iesve.com.

An annual license requires renewal every year. A Rolling license option is a onetime software purchase, which also requires 15% as an annual fee.  The 15% maintenance fee is for ongoing software upgrades and technical support.

Technical support (email, forum and phone) is included with any software purchase.

What is the difference between using the ‘Title 24’ Application in IESVE and using CBECC-Com which is developed by NORESCO?

The Title 24 Application in IESVE uses the CBECC-Com software ‘under-the-hood’ for doing Title 24 Compliance.  However, there are a number of advantages of using IESVE as a user-interface, namely:

  1. Using IESVE for Compliance unlocks the ‘detailed geometry’ mode of Title 24 compliance because it uses a 3D model. This 3D model is unavailable if using the default ‘simplified geometry’ mode natively in CBECC-Com.  This is important as the ‘detailed geometry’ mode allows additional energy savings by way of daylight harvesting, which is a requirement in the Title 24 energy code.  IES provides a free 3-Dimensional Application called ModelIT.  
  2. The two IESVE applications ModelIT (for Geometry) and Title 24 (for Compliance) are fully interoperable. There is no loss of information when revisions to the model geometry are made.
  3. The Title 24 application in IESVE software allows a tabular editing functionality, which allows commonly used functions: ‘copy, paste, import, export’. This allows for a much quicker population of building and space data.
  4. IES provides technical support by phone and email.
What Compliance paths are available, non-residential and residential?

IESVE supports the Non-Residential option only for Title 24 (2013 and 2016 Standards), although there is a Space Function type called “High-Rise Residential Living Spaces” which could be used for a mixed-use building. Please note that the Non-Residential path is taking the performance approach only, and generates the associated Compliance reports. The compliance types are further detailed below. This may be applied for new construction, existing or alterations.


Does the IES Title 24 Tool automatically generate the compliance forms?

Yes, the tool generates the NRCC-PRF-01 Compliance forms; also known as the Certificate of Compliance. You can view a partial example of a Certificate of Compliance below.


I am doing envelope only or envelope and lighting only Compliance. Do I need to specify the HVAC system in the Title 24 Application?

No, but you do need to assign Thermal Zones to the rooms. Thermal zones are required to allow the rules to assign HVAC equipment for the proposed and baseline models.

What if a material being used in my design is not listed in the material library?

You will need to select a material from the Project Materials library with similar thermal properties to the material being used. This CEC approach is mandated and is not an IESVE limitation.


I am receiving errors with room names. Can you offer any general guidance for the 3D model?

As the Title 24 module in the VE runs the CBECC-Com Ruleset & EnergyPlus simulation engine for compliance, there are a few limitations with regards to naming the rooms. Please note that these issues do not exist elsewhere in the VE:

  • The &, >, <, and $ symbols cannot be used.
  • No more than 10 rooms allowed per thermal zone.
  • Duplicate room names are not allowed. Each room and each zone must have a unique name.
  • Rooms on different floors cannot be on the same thermal zone.
  • The analysis will not be successful with any space or surface polygon (PolyLp in CBECC-Com) containing more than 120 vertices due to a limitation in the EnergyPlus simulation.
  • Self-shading surfaces (from ModelIT) are not accounted for in the Title 24 calculation.

Note that any construction name should also exclude any unusual alphanumeric characters.

I’m getting too many unmet load hours. What is the process for compliance when CBECC-Com (using IES Title 24 Application) determines the HVAC system for the proposed building is undersized?

When the simulation has more than 150 hours of unmet load hours, the HVAC system capacities (airflow and coil capacities) must be manually increased to meet the load, even if that does not represent the actual HVAC system design.  There is an exceptional condition that should be marked “Yes” when this is done, and a note will be added to the compliance report.

Please also refer to the ApacheHVAC application in IESVE for HVAC Sizing Calculations. See reports below.


How does the Title 24 application (using CBECC-Com) use daylighting controls in the simulation and what inputs are required?

CBECC-Com determines daylit zones from the geometry of the space and the locations of skylights and windows when valid fenestration constructions have been assigned. When lighting power is above 120 Watts in a daylit zone, daylighting controls are required. Daylighting inputs include the amount of lighting controlled and the daylighting control type. Three types of controls are available: Continuous, Continuous Plus Off, and Stepped Switching. The Continuous controls can operate at any fraction between the minimum and maximum power output. With the Continuous Plus Off controls, the minimum power output is zero. The Stepped Switching controls changes the lighting power output in discrete uniform steps.

Once the proposed compliance model is built, do we need to change anything on the baseline case, or will the baseline be generated automatically?

The standard model (or baseline) or is automatically generated and cannot be edited. 

What are the options for specifying lighting? Is lighting power density the only method used?

There are two options; the Area Category Method and the Tailored Method.

Lighting in the Area Category Method can be defined as a lighting power density (W/sf).  Alternatively, lighting systems can be defined by the Tailored Method which requires the definition of each lighting fixture and quantity of each fixture in the space.

Each lighting system can be assigned to a daylit area type for use with daylighting controls: Skylit, the portion of the floor that receives daylight from a skylight; Primary Sidelit, portion of the floor that receives the highest amount of daylight from a window; Secondary Sidelit, portion of the floor that receives a lower, but still useful, amount of light from a window; or none for that portion of the space which is not daylit.

My project is using packaged single zone rooftop units. When I enter my systems and attempt a Title 24 compliance analysis, I get an error message that terminal units are required. My project doesn't have terminal units. What is the problem?

The Title 24 Application does not use Apache, but rather CBECC/EnergyPlus. Terminal units are required by EnergyPlus as the connection between an air system and a thermal zone. In your case, the terminal units would have a type of "Uncontrolled" and corresponds to the grill through which supply air enters the space.

How can I claim Power Adjustment Fraction (PAF) credits in the Title 24 Application for the lighting in my space?

In CBECC-Com interior lights can be modelled by either simply specifying the lighting power density, or by building up a detailed lighting system. PAF credits can be claimed only with the InteriorLightingSystem method. Within the ‘Space Data>Interior Lighting’ tab, choose the PAF credit type applicable for your lighting system derived from the of ‘Lighting Controls’ drop down menu. The software will auto populate the PAF fraction and adjust the total lighting power based on the selection.

What are the import/export options available in IES-VE for Title 24?

Imports include SketchUp, AutoCAD, ArchiCAD, and anything supporting gbXML or IFC (e.g. from Revit or Vectorworks). There is a gbXML export, as well as copy/paste and import/export functionality when dealing with tabular edits (spreadsheet-style) for speedy population of models.

I am receiving an error about a “non-convex space”. Is there a problem with my geometry, specifically with a ‘C-shaped’ or ‘L-shaped’ room?

This has been a common issue reported to our technical support team, but is not always reproducible.  To understand the limitations of model geometry in OpenStudio/EnergyPlus (called upon by CBECC-Com), please watch the YouTube clip: https://www.youtube.com/watch?v=GzJSHQHTHy4. There have been some instances whereby simple model geometry from ModelIT has to be further simplified, so that there are no ‘C-shaped’ or ‘L-shaped’ rooms.

Please be aware that cutting rooms into separate simple 4-sided entities might throw the daylight zoning calculation off.

A so-called “non-convex” space or zone is one where one or more surfaces cannot “see” one or more of the other surfaces in the space or zone. A common example would be an “L” shaped zone.

When CBECC-Com calls upon EnergyPlus to run its “Solar Distribution” model, it should not have the detailed “FullInteriorAndExterior” setting engaged. CBECC-Com is set to run a simpler solar distribution model called “FullExterior”. In this case, beam solar radiation entering the zone is assumed to fall on the floor, where it is absorbed according to the floor's solar absorptance. Then any radiation reflected by the floor is added to the transmitted diffuse radiation, which is assumed to be uniformly distributed on all interior surfaces. Non-convex spaces or zones should not create problems when FullExterior solar distribution is used.

Can I use the Title 24 model for LEED submission (ASHRAE 90.1)?

You can use the same 3-D model, but not with the Title 24 Application. For ASHRAE 90.1 Compliance, you would rather open that same model and use the ASHRAE 90.1 Navigator which will automate the 90.1 modeling and reports (for LEED submittal). It also provides a detailed workflow so to accurately account for all building energy end-uses and energy costs.

I know it is possible to model a VRF system in ApacheHVAC and a natural ventilation system in MacroFlo, but how do I setup and simulate these types of systems within the Title 24 application?

Currently no alternative calculation methods are approved by the CEC for Title 24 compliance. All models are currently limited by the CBECC-Com Ruleset and the EnergyPlus simulation engine, which have no provisions for VRF systems or natural ventilation modeling.

In the meantime, the simple recommended approach from the CEC is modeling them as minimally efficient single split heat pump units for VRF. For Natural Ventilation, there is no recommended approach as of yet. 

The exceptional design process is really intended to be for building designs that cannot be modeled by the Title-24/CBECC-Com software engine. If a design cannot be modeled by the software, the designer should work with their building department and the CEC to get approval for the process.

I am modeling a Shell and Core office building and do not yet have HVAC sizes for the tenant spaces. Do you have a recommendation?

You can use the same HVAC sizes as the baseline model. These should be detailed in your project/ab folder. Check the .htm file for details.

Is it possible to do a TDV analysis through the Apache-based simulation?


For those unaware, TDV, or Time Dependent Valuation is the common metric used in the cost-effectiveness calculation for Title 24 Compliance and Utility Incentives. This allows the Title 24 Standards to provide a different metric (other than primary site energy usage) to building designers, encouraging them to design buildings that perform better during periods of high energy cost, which is often when the grid is in high-demand. The concept behind TDV is that energy conservation measures (ECMs) should be valued differently at different times to better reflect the actual costs to users, to the utility system, and to society.

There is a 5 step process.

  1. Open a TDV-result file in VistaPro after an energy simulation has been complete.

  2. The TDV files have an .apu extension and are located in your installation directory, shown below. Note there are 16 California climate zones. Select the CZ for your project.

  3. Once the TDV.apu file is imported, a new category becomes visible: Utility Schedule. Check this category ON, and you will see three TDV variables appear for gas, propane and electricity.  If you select one, or more, and graph them, you will see the varied hourly multipliers throughout the year.

  4. You can now see the TDV multiplier and the varied energy variables, but they are not merged to one variable, e.g. TDV-Electricity. To do so, use Custom Variables as shown below.

  5. The custom variables will now appear in your list, which can be view graphically, or exported as an 8,760 data file.