Building Modeling: What, Where, Why, and How?

Building Modeling – What, Where, Why, and How

By Blake McLam


As climate change compromises our collective future, we all have a stake in adapting to the changing landscape and finding solutions to build a more sustainable society. One of the most beneficial things happening in the building space, mostly behind the scenes, is building modeling. The built environment is cited by The Climate Group as contributing 40% of global emissions, and if left unchecked, those are set to double by 2050. Americans spend most of their lives indoors, so this fact shouldn’t be too alarming. What should be alarming is that the indoor concentrations of some pollutants are often 2 to 5 times higher than typical outdoor concentrations.

Concerns about both emissions and occupant wellness have led to many states adopting more stringent building and energy codes. Though there is no national energy code, states and towns have consistently based their energy codes on ASHRAE requirements, and more and more states are adopting a version of the International Energy Conservation Code. Luckily ASHRAE and IECC both have a robust building energy modeling methodology that facilitates prescriptive and performance targets that have been proven effective across all kinds of buildings and climates. 

Further, building owners have adopted even more stringent guidelines like LEED, WELL, and Fitwell certifications, which further their commitment to the environment and to the health of their building’s inhabitants. This is the reason for the ever-spreading adoption of energy modeling: both the public and private sector have seen the benefits of energy modeling on their building stock, which then get reiterated back into the energy code. The energy code is guided by political commitments, building best practices, and available technology. Our political commitment to achieving net zero emissions by 2050, the Paris Climate Agreement, and other initiatives continue pushing us to reduce carbon emissions. To improve the performance of buildings, we must track and review changes to see their effects over time.

With energy modeling, we can predict with near certainty how a proposed building will perform. We can analyze how utilizing different technologies for HVAC, envelope, or glazing would affect energy consumption. Further, through advanced commissioning, we can then measure the building’s real-world performance and adjust the modeling best practices to have more accurate models. At this point, energy modeling is supported by national tax incentives, as well as state and local energy codes. This article will illustrate who is showing the most interest in energy modeling and why, a summary of how much energy models have reduced energy consumption, and finally, how an energy model could benefit your construction.


First things first. What is energy modeling?

Energy modeling is typically a physics-based software simulation which replicates, as closely as possible, the real-life use conditions of a proposed or existing building. This considers the thermodynamic qualities of the building envelope, from the slab on grade all the way up to the roof, and everything in between. All power used to light the space inside and out is considered, along with all power used to ventilate the space. Water use, heating, and distribution are considered. Plug loads are input, based off projected end use. All power generated on the site is considered.

Finally, to make sense of the output data of the simulation, the model is usually compared to a typical or baseline case. The baseline is usually what we call a “code minimum” building (meaning an existing building that is up to code but not necessarily going above and beyond sustainability-wise), or an average of real buildings’ performance, depending on the rating system or code presiding over the design.


From our analysis, we pinpointed several states where energy modeling is popular, or is gaining popularity, and here I will speculate about why this may be the case. First, we will start with California and then move into some lesser-known areas of climate action.

California, where Verdical Group is headquartered, has the most progressive energy code in the country. The California Energy Code requires either a prescriptive or performance model for all new construction and major renovations. The prescriptive approach utilizes a strict yes or no approach for compliance. The performance approach allows some tradeoffs, say a high performing HVAC system with underperforming windows could allow for more net savings than the prescriptive case, and therefore is valid design. The actual energy models are mandatory for the construction permitting process guided by the California Energy Commission. California publishes new energy codes every three years with improvements and more stringent energy efficiency mandates. This current code cycle went into effect January 1st of 2023 and for the first time required solar PV and battery storage to be installed on all projects, with very few exceptions. Getting a building to pass code in California is not a walk in the park, even with a very strong design. Energy modeling has been a known challenge for developers and contractors in California for years, which is one of the reasons that we began offering the service to Verdical Group’s clients.  

Massachusetts is a state that surprised us. Massachusetts shows the highest number of Google searches about energy modeling. This is presumably due to the state’s newly adopted energy codes, including the “Stretch Code” which went into effect first for residential buildings in January and later for commercial buildings in July of 2023. The state also proposed a Specialized Code adequate for net zero energy projects. These codes advance on the “Base Code” which is (as of July 2023) the 2021 version of the International Energy Conservation Code. The codes that improve upon the base code appear to be voluntary by the town or city, but the adoption of the Stretch Code actually outnumbers the Base Code 6 to 1. Shout out to MA – it is very impressive that are implementing a Specialized Code for net zero buildings. We can’t wait to work on more projects in the Mayflower state!

Colorado ranks second in terms of energy modeling Google searches. This is likely due to a House Bill of 2019 which stated that statewide, every city and town should adopt and enforce one of the three most recent versions of the IECC. Considering the time that has lapsed since then, we can assume that the recent uptick in energy modeling searches indicates that towns and cities have begun to enforce these new regulations and are working to implement the energy modeling requirements prescribed in the codes. We have seen some great designs coming out of the Centennial State, keep it up CO!

Texas was another surprise to see at the top energy modeling search list. But with an independent energy grid, they likely benefit the most from improved energy efficiency in their building stock. Their energy code is based off the 2015 IECC code as well as the ASHRAE 90.1 2013 energy code. These codes, like the other states mentioned above, also include energy modeling as a prescriptive and performance mandatory requirement. Happy to see Texas fighting the good fight!


Now that we’ve discussed why energy modeling is becoming more popular in specific states, let’s focus on why energy modeling is important. Energy modeling allows for the comparison of building designs to facilitate the most cost-effective path to meeting energy performance goals for any type of building, in any location and climate. This gives us ever-improving standards for building efficient, effective buildings that will stand the test of time.

The California Energy Commission recently published a paper on the statewide impact of the 2022 energy code relative to the 2019 energy code. Annually, the code’s improvement just from 2019 to 2022 stands to reduce consumption and generate massive amounts of energy. One telling snip from the 2022 Energy Code Impact Analysis shares that these improvements will:

  • save 5,472 GBtus, 1,565 GWh, and 14.39 MTherms of site energy;
  • save 46,782 GTDV, 2,954 GBtu HSE, and 285,214 tonnes of C02e;
  • provide 123 MW of non-coincident peak demand reduction.

These Gigawatts and millions of therms saved are just from analyzing California’s incremental reduction from one round of energy code improvements. Overall, energy codes and modeling have had a much greater impact on the built environment than this shows.

The US Department of Energy published a visual showing the energy use index values of buildings built since the 1970s. As seen below, the MEC and later the IECC code have decreased the average building’s EUI by roughly 45% compared to 1975 levels. Then, ASHRAE 90.1 has decreased the average building’s EUI by roughly 54%. These are incredibly important steps as we reach our collective climate goals, and the results are in: energy modeling is working.  



How can you get involved? If you are planning on building your dream home, make sure to request that it meets or exceeds the local Energy Code requirements, and if you are in a place with no energy code, request it be built to the standards prescribed in either IECC or ASHRAE 90.1. If you are looking for a nice apartment or office, make sure to look at green building certified spaces. These spaces are sure to include thoughtful design revolving around deep energy efficiency, environmental stewardship, and occupant comfort.

Are you an Architect or Contractor and codes are getting you down? This is what we do here at Verdical Group. We manage green building certifications and code compliance, from beginning design, to energy modeling, down to the last commissioning visit. We have experience and expertise in services like LEED, WELL, Fitwell, ActiveScore, ESG development, CalGREEN, life cycle assessments (LCAs), green events, PV design, commissioning, and sustainability training. Please reach out with any questions about which codes apply to your project, how energy modeling can help you reach your targets, and which green building certification might fit best for your project