Energy Code Update Options
 

The City of Flagstaff is evaluating and preparing to adopt the 2024 suite of model Building and Fire Codes—the 2024 Suite of Codes—published by the International Code Council (ICC), with local amendments. The IECC is the most effective tool to reduce building energy use in new buildings, support long-term affordability through utility cost savings, and improve health outcomes.

City staff will present four energy code options for Council consideration, ranging from the least to most aggressive in meeting Flagstaff’s adopted climate goals. The IECC (or energy code) consists of a base code and optional appendices that cities can adopt (often with local amendments) to advance energy efficiency locally. The four energy code options represent different ways to use the IECC: each option includes a distinct combination of IECC amendments and appendices that Flagstaff could adopt. Staff request Council direction on which option to explore as part of the larger Building and Fire Code update process.

1. What energy code option should staff explore?
2. Should staff explore other Energy Code options, beyond those presented here?
3. What “complementary” code options should staff explore, if any?
4. What additional information will be helpful to include when staff return to Council with proposed Energy Code updates in mid-2026?

 

• Step 1: April 8: City Council presentation - Introduction to Building and Fire Codes.
  • Recording available here: https://www.youtube.com/live/LiPRlV9owLM?t=5390s; time stamp is 1:29:50.
• Step 2: September 25 – December: Staff review key changes from 2018 – 2024 for all codes
• Step 3: TODAY, December 16, 2025: Energy Code Update Options  

2026:

• Step 4: January: Staff draft potential code revisions.
• Step 5: January - February: review and vet key code changes and potential local amendments for all codes with the City staff, the Building and Fire Codes Board of Appeals, developers, City Commissions, and the public (including open houses)
• Step 6: March: Incorporate feedback into proposed codes + City Attorney’s Office full legal review of all proposed codes and local amendments
• Step 7: April/May: City Council Work Sessions
• Step 8: June/July: City Council – code adoption

The City of Flagstaff’s Building Safety Section is leading the Building Code update effort in partnership with the Fire Department, the Sustainability Division, and other City divisions (Sustainability is assisting due to the critical impacts of the energy code on the City’s climate goals). 

2. Focus of this Presentation
Staff seek Council direction on advancing energy efficiency standards to meet Flagstaff’s carbon neutrality goals. Reducing energy use and greenhouse gas emissions from buildings is essential to achieving carbon neutrality by 2030. The Flagstaff Carbon Neutrality Plan contains several strategies for reducing emissions in the built environment, including for new residential construction to be net-zero energy by 2030 (net-zero homes are extremely energy efficient, and energy use is offset by renewable energy from solar panels).

Staff identified four energy code options for Council consideration. The IECC (or energy code) consists of a base code and optional appendices that cities can adopt (often with local amendments) to advance energy efficiency locally. The four energy code options represent different ways to use the IECC: each option includes a distinct combination of IECC amendments and appendices that Flagstaff could adopt.  Option 1 provides no improvement in energy efficiency and makes the least progress towards Flagstaff’s carbon neutrality goals; Option 4 provides the greatest improvement in energy efficiency and progress towards carbon neutrality goals.

• Option 1: No change. Keep the 2018 IECC and decline to adopt the 2024 IECC (a 0% improvement in energy efficiency).
• Option 2: Stay the course. Adopt the 2024 IECC base code and minor appendices (a 15%-29% improvement in energy efficiency).
• Option 3: Progress to net-zero. Adopt the 2024 IECC base code, minor appendices, and the  ‘stretch’ code appendix (a 24%-34%+ improvement in energy efficiency).
• Option 4: Net-zero-ready. Adopt the 2024 IECC base code, minor appendices, and the net-zero-ready appendix (31% - 42% improvement in energy efficiency).

Staff also seek direction on whether staff should explore two “complementary” code options:

1. Allowing new large multifamily residential buildings to opt into the residential energy code.
2. Requirements for radon mitigation and/or testing in new homes.

3. Energy Code Overview
The energy code primarily applies to new construction. The 2024 IECC includes a base code and optional appendices to enhance energy efficiency beyond the base code. Each edition reflects advancements in technology and building science, incorporating cost-effectiveness, lessons learned, and expert consensus from thousands of contributors nationwide.

The IECC includes separate Residential and Commercial standards. The Residential code covers low-rise housing (up to three stories), while the Commercial code applies to all other buildings, including larger multifamily structures. Commercial standards are slightly more stringent, and both codes offer flexible compliance options for builders.

3. Why Adopt a Strong Energy Code?

Staff developed their approach to energy code options based on a core set of principles aimed at improving affordability through long-term utility cost savings, enhancing public health, and reducing energy consumption in new construction across Flagstaff.

1. We are building for the next 75+ years
Buildings can last over a century, so today’s decisions will shape Flagstaff’s housing for generations. Durable, adaptable homes, like those in historic neighborhoods, have served diverse residents over time. While new housing may start as high-end, it often becomes middle-income through market filtering. Modern homes must also support emerging technologies, from energy management to climate resilience. Updating building codes is a key opportunity to ensure new construction meets future needs and challenges.

2. Healthier, more efficient buildings can benefit everyone
Strong energy codes ensure all new buildings, whether luxury homes, affordable housing, or commercial spaces, are healthy, comfortable, and energy-efficient. These standards benefit everyone, reducing utility costs, supporting climate goals, and promoting equity across all communities, now and for future generations.

3. Utility costs are projected to increase over the next 75+ years
Utility prices are projected to increase due to the cancellation of renewable energy projects, extreme weather conditions, supply constraints, and rising demand. Both APS and UniSource—the natural gas provider for Flagstaff—have rate increase cases before the Arizona Corporation Commission, which regulates utilities in Arizona. Although exact future rate increases are unknown, energy-efficient buildings will save residents money over the next 75+ years by partially insulating them from utility price increases.

4. Energy efficiency and lower monthly utility costs can help with affordability
Energy codes are a key climate tool, but must align with Flagstaff’s urgent housing needs. The Building and Fire Code update presents an opportunity to advance both goals by promoting energy-efficient, climate-resilient buildings that reduce utility costs, enhance health, and support long-term affordability. Higher efficiency at construction can save residents thousands over time, helping them stay in their homes as energy costs rise.

5. Energy efficiency features are a small percentage of total housing construction costs
Energy codes account for a small portion of overall construction costs, which are primarily driven by factors such as home size, materials, layout, and finishes. Unlike many design choices, energy efficiency features pay off over time through lower utility bills. According to the National Association of Homebuilders, construction costs make up just 64.4% of a home’s final price. The table below shows the components that contribute to the final sales price of a new single-family home (national average). The average sales price in Flagstaff in November 2025 for a new single-family home was  $911,037. Many energy upgrades cost less than the 2.8% (of the average Flagstaff sales price) spent on sales commissions.

Figure 1: Results from the most recent National Association of Homebuilders (NAHB) national study of single-family home price and cost breakdowns.

Source: National Association of Home Builders (NAHB) (2025). 

6. The Energy Code is linked to other development code changes
It is important to consider how potential Energy Code updates are related to, and impact, other development codes.  Updates to other Building and Fire codes may also impact housing construction costs (the Energy Code is one of only 15 codes in the 2024 Suite of Codes).  For example, a stronger Energy Code may reduce the need to incentivize or require additional energy efficiency standards in the Zoning Code, for example.

It is also important to consider how development codes impact costs holistically.  Recent Zoning Code changes, including for Middle Housing, Resource Protection standards, Accessory Dwelling units, the Zoning Map Amendment Process, the Subdivision Review Process, and others, are intended to streamline standards and processes, thereby reducing barriers to building housing in Flagstaff.

Potential future development changes, especially those resulting from the Code Analysis Project (LASS+CAP), could continue to reduce barriers to housing development, including reducing costs. For example, reducing parking can save $3,000 to $35,000+ per space, while increasing density and/or decreasing unit sizes can lower the cost per unit. Reducing off-site transportation improvements could save tens to hundreds of thousands of dollars, depending on the scope of the improvement (the final CAP report will be delivered in 2026 and will provide code and policy recommendations and estimated cost impacts). In this context, additional construction costs from the Energy Code would be more than offset by cost savings associated with other code changes, in addition to long-term utility cost savings from energy efficiency improvements.

7. The Energy Code supports resilience to extreme weather and grid outages
Energy-efficient, well-insulated, air-tight buildings protect residents from wildfire smoke, extreme heat, and cold. When the power goes out, they also stay livable for longer than poorly insulated buildings. A Rocky Mountain Institute study found that homes built with higher energy codes retained heat significantly longer during a simulated cold snap, with the highest-efficiency homes lasting six days before dropping below 40°F. In contrast, a typical 1950s home took only 8 hours to drop below 40°F (report available here: https://rmi.org/wp-content/uploads/2020/02/Hours-of-Safety-insight-brief.pdf).

8. Flagstaff has a unique climate in Arizona, and we can learn from other peer cities
Flagstaff is in Climate Zone 5B (Cool, Dry). In contrast, Phoenix and Tucson are in Climate Zone 2B (Hot, Dry), and Prescott is in Climate Zone 4B (Mixed, Dry). The Pacific Northwest National Laboratory found the 2024 Residential IECC improves energy efficiency over the 2018 IECC in each of these climate zones (2B: 17.1% , 4B: 16.7%,  5B: 15.2%). Differences are due to the variation in building energy use across the climate zones. Flagstaff can learn from other cities and towns in Climate Zone 5B across the Mountain West that are national leaders in advancing energy efficiency, including Denver and Boulder.

9. The Energy Code is one of the most effective ways to accelerate climate action
In 2023, 55% of Flagstaff’s greenhouse gas emissions came from building energy. Residential buildings accounted for almost 39% of these emissions. Flagstaff needs to drastically reduce energy use and emissions from buildings to achieve carbon neutrality by 2030. The recent Analysis of the Costs, Benefits, and Barriers to Building Highly Energy-Efficient and All-Electric Residential Homes in Flagstaff, Arizona (presented to City Council on December 9, 2025) found that improving energy efficiency by approximately 24% over Flagstaff’s current code resulted in an 18-58% reduction in greenhouse gas emissions.

Specifically, the adopted CNP calls for new homes to be net-zero energy by 2030, which would reduce greenhouse gas emissions from buildings by 100% over Flagstaff’s current code. Net-zero homes deliver extremely low utility bills, greater comfort, and zero operational emissions. Adopting  strong energy codes now is a critical step toward  reducing energy use and emissions from new construction.

10. Local amendments will help fit the code to our local needs
Municipalities often choose to adopt model codes, including the Energy Code (base code and appendices), with local amendments to make the code better fit the local context. Local amendments can include additions, deletions, and modifications (the City adopted the 2018 IECC with local amendments). Once staff receive Council direction, staff will work with the Building and Fire Code Board of Appeals, builders, and the Flagstaff community to identify appropriate amendments and bring them back to Council in mid-2026. It is likely that the final package of Energy Code updates brought back to Council will look slightly different than the options presented here. 

5. Overview of Energy Code Options
To develop the energy code options, City staff looked to Arizona cities and energy code leaders across the country, especially in Colorado, where many cities have a similar climate to Flagstaff. Staff organized the 2024 IECC amendments and appendices into four options. Option 1 makes no improvement in energy efficiency; Option 4 makes the greatest improvement and progress toward Flagstaff’s climate goals. Detailed information about the 2024 IECC and appendices is provided as an attachment.

Table 1: Residential Energy Code Options

Option 1: No change 0% improvement in energy efficiency	Option 2: Stay the course 15% improvement in energy efficiency	Option 3:  Progress to net-zero 24% improvement in energy efficiency	Option 4: Net-zero-ready 31+% improvement in energy efficiency
Keep Flagstaff’s current energy code (decline to adopt the 2024 IECC)	2024 IECC with local amendments: 95% efficient gas furnace Cold climate heat pump Large multifamily can opt into the Residential IECC	2024 IECC with local amendments: 95% efficient gas furnace Cold climate heat pump Large multifamily can opt into the Residential IECC	2024 IECC with local amendments: 95% efficient gas furnace Cold climate heat pump Large multifamily can opt into the Residential IECC
	Appendix RE Electric Vehicle Charging Infrastructure	Appendix RE Electric Vehicle Charging Infrastructure	Appendix RE Electric Vehicle Charging Infrastructure
	Appendix RK Electric-Ready Residential Building Provisions	Appendix RK Electric-Ready Residential Building Provisions	Appendix RK Electric-Ready Residential Building Provisions
	Appendix RB Solar-Ready Provisions–Detached One- and Two-Family Dwellings and Townhouses	Appendix RL Renewable Energy Infrastructure	Appendix RL Renewable Energy Infrastructure
		Appendix RG 2024 IECC Stretch Code	Appendix RC Zero Net Energy Residential Building Provisions

Table 2: Commercial IECC Energy Code Options
 

Option 1: No change 0% improvement	Option 2: Stay the course 29% improvement	Option 3: Progress to net-zero 34%+ improvement	Option 4: Net-zero-ready 42% improvement
Keep Flagstaff’s current energy code (decline to adopt the 2024 IECC)	2024 IECC with local amendments: 95% efficient gas furnace Cold climate heat pump Large multifamily can opt into the Residential IECC	2024 IECC with local amendments: 95% efficient gas furnace Cold climate heat pump Large multifamily can opt into the Residential IECC	2024 IECC with local amendments: 95% efficient gas furnace Cold climate heat pump Large multifamily can opt into the Residential IECC
	Appendix CB Solar-Ready Zone—Commercial	Appendix CB Solar-Ready Zone—Commercial	Appendix CB Solar-Ready Zone—Commercial
	Appendix CG Electric Vehicle Charging Infrastructure	Appendix CG Electric Vehicle Charging Infrastructure	Appendix CG Electric Vehicle Charging Infrastructure
	Appendix CH Electric-Ready Commercial Building Provisions	Appendix CH Electric-Ready Commercial Building Provisions	Appendix CH Electric-Ready Commercial Building Provisions
		Appendix CI Demand Responsive Controls	Appendix CI Demand Responsive Controls
		Appendix CE Required HVAC Total System Performance	Appendix CD the 2030 Glide Path
		Appendix CF Energy Credits

Option 1: No change from current code (0% improvement in energy efficiency)
Option 1 keeps Flagstaff’s current energy code (the 2018 IECC) and keeps new construction at the current required level of energy efficiency. It veers from Flagstaff’s past Building and Fire Code updates by declining to adopt the most current energy code. It holds Flagstaff back from meeting carbon neutrality goals for new construction by 2030 and will require a massive improvement in energy efficiency to get to net-zero in the next Building and Fire Code update.

Option 2: Maintain Flagstaff’s current course (15% - 29% improvement in energy efficiency)
Option 2 adopts the base 2024 IECC with minor appendices. It is a similar approach to the City’s recent energy code update. Option 2 reduces energy use while adding new standards for electric-ready construction. It is better than Option 1 for energy efficiency, but it still holds Flagstaff back from meeting its carbon neutrality goals for new construction by 2030. It will require a dramatic increase in energy efficiency to get to net-zero in the next Building and Fire Code update.

Option 3: Intermediate step to net-zero (24% - 34% improvement in energy efficiency)
Option 3 builds on Option 2 and is an intermediate step to net-zero construction. It takes a more aggressive approach to energy efficiency. Option 3 builds on Option 2 by including stronger standards for solar-readiness and energy efficiency. Option 3 is better than Options 1 and 2 for energy efficiency, and it moves Flagstaff closer to meeting its carbon neutrality goals for new construction by 2030. It will require an increase in energy efficiency to get to net-zero in the next Building and Fire Code update.

Option 4: Net-zero-ready construction (31% - 42% improvement in energy efficiency)
Option 4 gets to net-zero-ready new construction. It builds on Option 3 by including stronger energy efficiency standards. Net-zero-ready buildings can easily become net-zero with the future addition of solar panels to offset their annual energy use. Net-zero-ready homes include energy efficiency improvements to the building envelope that are easy to install during construction, but extremely difficult to retrofit. Option 4 is better than Options 1-3 for energy efficiency, and it gets Flagstaff on track to meet its carbon neutrality goals for new construction by 2030. The next Building and Fire Code update will need to require new construction to install solar panels to offset annual energy use to get to net-zero.

Beyond Option 4: Net-zero construction (100% improvement in energy efficiency)
To meet the Carbon Neutrality Plan goal for net-zero construction, Council can require net-zero construction now (five years ahead of the 2030 goal) or choose to require net-zero construction in the next building code update.

Cost Implications of Energy Code Options
Estimates of the impacts of the Energy Code options on construction costs and utility cost savings are provided in the presentation and other attachments. Costs and savings are provided as a range (when multiple data points are available). Values should be taken as a ballpark estimate, given the potential for large variations in construction costs and utility savings based on building type, available electricity rate plans, heating and cooling system types, actual future utility cost increases, building occupant behavior, and other external factors.

Estimates are based on multiple local and national data sources. Local Flagstaff data is primarily from the recent Analysis of the Costs, Benefits, and Barriers to Building Highly Energy-Efficient and All-Electric Residential Homes in Flagstaff, Arizona (presented to Council on December 9, 2025). National data sources include: the National Association of Homebuilders (NAHB), the Rocky Mountain Institute (RMI), and the Department of Energy (DOE), including the Pacific Northwest National Laboratory (PNNL) and the Energy Information Administration (EIA).