Energy Code for Existing Commercial Building Projects

Overview

Existing commercial buildings undergoing an addition, alteration, and/or change of occupancy or use must follow the requirements in Chapter 5 Existing Buildings of the Denver Energy Code. A given project may need to observe the requirements in more than one section, depending on the existing conditions and scope of work for each area of the building. Chapter 5 also covers work on historic buildings or buildings undergoing repairs. The sections below outline the requirements based on the 2025 Denver Energy Code 2nd printing or later for each type of project and provide example scenarios to help clarify your options for compliance.

In addition to Denver Energy Code compliance, your project may also have to comply with the Denver Green Code, Denver Green Buildings Ordinance, and/or the Energize Denver Ordinance.

Definitions and Table C505.1 Energy-Demand Categories

Project Type	Description
Addition	An extension or increase in the conditioned space floor area, the number of stories, or the height of a building or structure
Alteration	Any construction, retrofit, or renovation to an existing structure other than a repair or addition. An alteration can also be a change in a building's electrical, gas, mechanical, or plumbing system that involves an extension, addition, or change to the arrangement, type or purpose of the original installation.
Change of Occupancy or Use	Change of occupancy occurs when a change in the use of a building or a portion of a building results in a: Change of occupancy classification Change from one group to another group within an occupancy classification Any change in use within a group for which there is a change in the application of Energy Code requirements. Spaces undergoing a change in occupancy to a higher energy-demand category (as shown in Table C505.1 below) must follow the Denver Energy Code for Change of Occupancy or Use.
Repairs	The reconstruction or renewal of any part of an existing building for the purpose of its maintenance or to correct damage.

Change of Occupancy or Use Table C505.1 Energy-Demand Categories

Energy-Demand Category	International Building Code Occupancies	International Residential Code Structures
4 (highest energy-demand)	A
3	E, I-4
2	B, I-1, I-2, I-3, M, R	One- and two-family dwellings and townhouses
1 (lowest energy-demand)	F, H, S, U	Accessory structures with or without living space

Considerations Before Starting A Project

Is the project a first tenant finish?

If the project is first tenant finish, projects which are the first-time build out of any space(s) in a core and shell building that have not been previously occupied, see the core and shell building permit drawings to identify the requirements for the tenant. The requirements for the first tenant finish are described in the policy “DEC and DGC Compliance for Core and Shell and Tenant Finish.” The policy provides additional guidance for meeting Denver Energy Code sections C406.1.1 First tenant finish spaces, C404.12 Water heating equipment location, and C405.15 Additional electric infrastructure and the All-Electric Property designation.

Are you completing roof work and will it need to comply with the Denver Energy Code?

Roof recover is the process of installing an additional roof covering over an existing roof covering. It is exempt from Denver Energy Code compliance per C503.1(5).

Roof repair is the reconstruction or renewal of an existing roof for the purposes of its maintenance. It is exempt from Denver Energy Code compliance per C504.2(2).

Roof replacement is the process of removing the existing roof covering, repairing any damaged substrate, and installing a new roof covering. The roof must be brought up to code if the existing roof assembly is part of the thermal envelope and contains insulation entirely above roof deck per C503.2.1.

Will the roof work need to comply with the Denver Green Buildings Ordinance?

Buildings 25,000 sq. ft. and larger must comply with the Denver Green Buildings Ordinance when completing a roof recover or replacement. Additions 25,000 sf. ft. and larger must comply with Denver Green Buildings Ordinance.
While air barriers are not required where the work does not include alterations or repairs to the remainder of the building envelope per the Denver Energy Code C503.1(6), where a roof recover or replacement introduces a cool roof, the Denver Green Buildings Ordinance may require air barrier and other roof components to minimize condensation.

Are there any gas-fired systems or equipment in the existing building proposed to be replaced?

You can consider changing this equipment to heat pump instead of a like-for-like gas system. Denver has incentives that are available to help commercial and multifamily buildings replace their aging gas-fired equipment with heat pumps.

Check if the system type included in the Denver Energy Code partial electrification requirements in C503.3.3 and C503.4.1

Is the electrical service provided to the building sufficient for future electrification?

If not, consider upgrading it now or making a plan for a future upgrade.

If the project is first tenant finish, projects which are the first-time build out of any space(s) in a core and shell building that have not been previously occupied, see the core and shell building permit drawings to identify the electrification requirements for the tenant. First tenant finish projects must comply C405.15 Additional Electric Infrastructure for combustion equipment. Projects must also comply with the All-Electric Property designation with no permanent fossil fuel infrastructure if that was selected by the core and shell building.

Does the project qualify as a historic building?

If yes, the project is exempt from the Denver Energy Code if it is able to provide one of the following:

A report signed by the owner and a registered design professional demonstrating that compliance with a provision of the building code would threaten, degrade, or destroy the historic character or features, or the historic materials, form, or function
Letter from the Colorado State Historic Preservation Officer
Documentation from the Denver Landmark Preservation Commission or the Lower Downtown Design Review Commission

Will the project be required to comply with the 2022 Denver Green Code limited mandatory use requirements?

Commercial building projects that are major renovations, commercial as well as new buildings must comply with Denver Green Code limited mandatory use requirements. The Denver Green Code defines major renovations, commercial as alterations that are level 3 as defined in Section 604 of the Denver Building Code and also additions that are the lesser of 100,000 sq. ft. or 50% of the existing project gross floor area.

How large is your building and how will it comply with Energize Denver?

Buildings 25,000 sq. ft. and larger must comply with the Energize Denver annual Benchmarking requirements and Building Performance Standards. Think about how this project will impact the building’s ability to meet the Energize Denver performance target.

Buildings 5,000 – 24,999 sq. ft. are required to meet Energize Denver prescriptive performance requirements for this building size classification. Think about whether this project can help you meet those requirements.

Code Compliance Based on Project Scope

Additions

Denver Energy Code Compliance(PDF, 2MB)	Comply with Section C502 The addition must conform to the provisions of the Denver Energy Code as they relate to new construction Unaltered portions of the existing building/system are not required to comply with the energy code Gas-fired warm-air furnaces, unitary air conditioner/condensing units serving a heated space, and gas-fired storage or instantaneous water heaters shall comply with sections C503.3.3 or C503.4.1 Compliance path options: Prescriptive: Sections C402, C403, C404, C405, C406 (unless using an exception in C502.3.7), C408 and C502.3. Requires the Commercial Denver Energy Code Prescriptive Checklist(XLSX, 2MB) and COMCheck. - OR - Performance: Section C407 using modeling procedures from C407 for energy cost OR Appendix SE for site energy plus mandatory requirements. If the addition by itself cannot comply, trade-offs are allowed by modification to one or more existing components. Requires the Commercial Denver Energy Code Performance Checklist(XLSX, 927KB) and an energy model report.
Green Buildings Ordinance Compliance	If the addition is 25,000 sq. ft. or larger compliance is required. This includes installing a cool roof plus a compliance option
Denver Green Code - Limited Mandatory Use Provisions	Additions must comply with the limited mandatory use provisions of the 2022 Denver Green Code for Major Renovations, Commercial per section 101.4.1 if: The addition is either 100,000 sq. ft. or more - OR - The addition gross floor area is greater than 50% of the existing gross floor area
Energize Denver Ordinance Compliance	If the building with the addition is 25,000 sq. ft. or larger, the building will have to comply with Energize Denver’s Annual Benchmarking and Building Performance Standards. You should: Review the Energy Use Intensity performance requirements for your building use type Consider energy efficiency design measures, on-site PV installation, and/or partial or full electrification

Alterations

Denver Energy Code Compliance(PDF, 2MB)	Comply with Section C503 unless the scope is an exception outlined in C503.1 The altered building/structure cannot be less conforming to the provisions of the Denver Energy Code than the existing building Alterations must conform to the provisions of the Denver Energy Code as those provisions relate to new construction. Unaltered portions of the existing building/system are not required to comply New or replacement gas-fired warm-air furnaces, unitary air conditioner/condensing units serving a heated space, and gas-fired storage or instantaneous water heaters shall comply with sections C503.3.3 or C503.4.1 Compliance path options: Prescriptive: Sections C402, C403, C404, C405, C408 as required per C503.2 through C503.5. Requires the Commercial Denver Energy Code Prescriptive Checklist(XLSX, 2MB) and COMCheck. C406 is not required. - OR - Performance: Section C407.1.2 using modeling procedures from C407 for energy cost OR Appendix SE for site energy with special modeling rules for known and unknown conditions from C503.1.1. Compliance is either C503.1.1 energy cost or energy use of alterations is less than or equal to the existing building or C407.1.2 energy cost or energy use with a 10% additional allowance added to the target (PCIt or PSEIt). Requires the Commercial Denver Energy Code Performance Checklist(XLSX, 927KB) and an energy model report.
Green Buildings Ordinance Compliance	If a roof permit is required for 5% or more of the roof area and the building is 25,000 sq. ft. or larger, compliance with the Green Buildings Ordinance is required. This includes: Roof replacement: installing a cool roof plus a compliance option Roof recover: cool roof only
Denver Green Code - Limited Mandatory Use Provisions	Alterations that qualify as level 3 as defined in Section 604 of the Denver Existing Building code meet the Denver Green Code definition of “major renovations, commercial.” Level 3 alterations are where the work area exceeds 50 percent of the original building area or more than 10 parking spaces are substantially modified. These projects must comply with the limited mandatory use provisions of the 2022 Denver Green Code for Major Renovations, Commercial per section 101.4.1
Energize Denver Ordinance Compliance	If the building is 25,000 sq. ft. or larger, the building will have to comply with the Energize Denver annual Benchmarking requirements, and Building Performance Standards, and also electrification upon system replacements. You should: Review the Energy Use Intensity performance requirements for your building use type Consider energy efficiency design measures, on-site PV installation, and/or partial or full electrification Review your mechanical and plumbing systems and consider electrification when doing system replacement.

Change of Occupancy or Use

Denver Energy Code Compliance(PDF, 2MB)	Spaces undergoing a change in occupancy or use that would result in an increase in demand for either fossil fuel or electrical energy in Table C505.1 must comply with the Denver Energy Code Section C505. Where it is calculated that the change in occupancy or alterations will not result in an increase in demand for fossil fuel and electrical energy, the space shall comply with the Denver Energy Code requirements of this code for alterations. There is an exception for change in occupancy less than 5,000 sf when the current occupancy is not F, H, S, U or an accessory structure. Compliance path options: Prescriptive: C402, C405.2, C405.3, and C408. C406 is not required. Where section C402.1.5 component performance alternative is used, the proposed UA has an additional 10% allowance. Requires the Commercial Denver Energy Code Prescriptive Checklist(XLSX, 2MB) and COMCheck. - OR – Performance: Section C407.1.2 using modeling procedures from C407 for energy cost OR Appendix SE for site energy use plus mandatory requirements. The energy target has a 10% additional allowance. Requires the Commercial Denver Energy Code Performance Checklist(XLSX, 927KB) and an energy model report.
Green Buildings Ordinance Compliance	The Green Buildings Ordinance is not triggered by a change of use but review the scope. If a roof permit is required for 5% or more of the roof area and the building is 25,000 sq. ft. or larger, Green Buildings Ordinance compliance is required.
Denver Green Code - Limited Mandatory Use Provisions	Denver Green Code is not triggered by a change of use but review the scope. Scope that qualifies as level 3 alterations as defined in Section 604 of the Denver Existing Building code meets the Denver Green Code definition of “major renovations, commercial” and must comply with the limited mandatory use provisions of the 2022 Denver Green Code for Major Renovations, Commercial per section 101.4.1. Projects with level 3 alterations are where the work area exceeds 50 percent of the original building area or more than 10 parking spaces are substantially modified.
Energize Denver Ordinance Compliance	If the building is 25,000 sq. ft. or larger, the building will have to comply with Energize Denver’s Annual Benchmarking and Building Performance Standards. You should: Review the Energy Use Intensity performance requirements for your building use type Consider energy efficiency design measures, on-site PV installation, and/or partial or full electrification Review your mechanical and plumbing systems and consider electrification when doing system replacement.

Example Scenarios

Example 1: Alteration + Change of Occupancy or Use

An existing office building (120,000 sq. ft.) is converting to a multifamily building. The scope includes:

Mechanical and domestic water heating equipment replacement
Lighting replacement
Punched openings for a few new windows
Roof replacement

This project is an Alteration with a Change of Occupancy or Use, but the change of occupancy does not result in a change in energy-demand category per Table C505.1. Therefore, it must comply with the alterations section of the code.

Denver Energy Code Compliance

To comply with the Denver Energy Code, the project must comply with Section C503 alterations. The project has the option to comply with the energy code via the prescriptive path OR one of the performance pathways:

Prescriptive:
- Altered portions of the building must comply with the applicable requirements of sections C402, C403, C404, C405, and C408, as required per C503.2 through C503.5
- Unaltered portions of the building are not required to comply
Performance:
- Follow C407 OR Appendix SE plus mandatory requirements
- Unaltered portions of the building are modeled as existing conditions if known in the baseline and proposed models per C503.1.1
- Comply with either C503.1.1 energy cost or energy use of alterations less than or equal to existing building -OR- C407.1.2 energy cost or energy use with a 10% additional allowance added to the target (PCIt or PSEIt)

If any of the space heating or service water heating equipment included in the project scope is gas-fired warm air furnaces, unitary air conditioners or condensing units serving a heated space, or gas-fired storage or instantaneous water heaters, the project must comply with sections C503.3.2, C503.3.3 and/or C503.4.1.

Green Building Ordinance Compliance

The building is 25,000 sq. ft. or greater and will need a roof permit. This project must comply with the Green Buildings Ordinance by including a cool roof and an additional compliance option (such as a Green Building Certification).

2022 Denver Green Code Compliance

The project qualifies as a “major renovation, commercial.” It must comply with the limited mandatory use provisions of the 2022 Denver Green Code per section 101.4.1 for Limited Mandatory Use.

Energize Denver Compliance

Because the project is larger than 25,000 sq. ft. it is subject to the Energize Denver annual Benchmarking requirements and Building Performance Standards. Since the building is changing to a different use-type, the project team should become familiar with the new building performance interim and final targets it will have to meet. From the Energize Denver Technical Guidance, multifamily housing has a 2030 target of 44.2 kBtu/sf. The team should consider making a plan for compliance that may include:

Energy efficiency upgrades
Partial or full electrification
Installation of on-site PV
Energy modeling

Because Denver encourages adaptive reuse, the project can explore Alternative Compliance Options if needed.

Example 2: Alteration and Addition

An existing church (2 stories) is undergoing a renovation (of 75,000 sq. ft.) and an addition (of 20,000 sq. ft.). The renovation scope includes:

Lighting retrofits
HVAC system upgrades
Window replacements

The addition scope includes:

A new wing
Additional parking

The existing portion of the project must comply with the alterations section. The new portion of the project is an addition, so it will comply with the additions section.

Denver Energy Code Compliance

To comply with the Denver Energy Code, the project must comply with section C503 for the alteration and C502 for the addition. Each portion of the project has the option to comply with the energy code via the prescriptive path OR one of the performance pathways:

Alteration

Prescriptive:
- Altered portions of the building must comply with the applicable requirements of sections C402, C403, C404, C405, and C408, as required per C503.2 through C503.5
- Unaltered portions of the building are not required to comply

Performance:
- Follow C407 OR Appendix SE plus mandatory requirements. The energy target has a 10% additional allowance
- Unaltered portions of the building are modeled as existing conditions if known in the baseline and proposed models per C503.1.1

Addition

Prescriptive:
- The addition must comply with the applicable requirements of sections C402, C403, C404, C405, C406, and C408, as required per C502.3

Performance:
- Follow C407 OR Appendix SE plus mandatory requirements

If any of the space heating or service water heating equipment included in the project scope is gas-fired warm air furnaces, unitary air conditioners or condensing units serving a heated space, gas-fired storage or instantaneous water heaters, the project must comply with sections C503.3.2, C503.3.3 and/or C503.4.1.

Under the performance path, if the addition by itself cannot comply, the addition and alteration can be combined. The project team can modify one or more existing components as a trade-off to meet compliance requirements.

Regardless of which compliance path the project team chooses, the addition must comply with air leakage testing requirement (C402.5). The new parking lot must comply with electric vehicle supply equipment requirement (C405.13).

Green Building Ordinance Compliance

The alteration does not require a roof permit and the addition is less than 25,000 sq. ft. Neither part of this project has to comply with the Green Buildings Ordinance.

2022 Denver Green Code Compliance

The area of the addition is not 50% or more of the GSF and does not meet the definition of “major renovations, commercial.” However, the alterations project meets the definition of a “major renovation, commercial” because it is assumed to be a level 3 alteration for purposes of this example. Therefore, the project must comply with the limited mandatory use provisions of the 2022 Denver Green Code per section 101.4.1 for Limited Mandatory Use.

Energize Denver Compliance

Because the building was larger than 25,000 sq. ft. before the addition, it is subject to the Energize Denver annual Benchmarking requirements and Building Performance Standards. The team should investigate how the alteration and addition will affect the building's Energy Use Intensity and whether it should pursue any Alternate Compliance Options. Because of the larger square footage and the significant nature of the scope, the project should evaluate the Energize Denver 2030 target for Energy Use Intensity (EUI in kBtu/sf) and any applicable interim EUI requirements early in the design process. From the Energize Denver Technical Guidance, worship facility has a 2030 target of 42.1 kBtu/sf. The project team should make a plan for compliance that may include:

Energy efficiency upgrades
Partial or full electrification
Installation of on-site PV
Energy modeling

Example 3: Alteration and Change of Use or Occupancy

An existing retail building (5,500 sq. ft.) is undergoing a change of occupancy to a restaurant. The renovation scope includes:

Mechanical and plumbing upgrades
Lighting replacements
New exterior wall insulation
New exterior overhead door

This project is a change of occupancy resulting per Table C505.1 in a higher energy-demand category because it goes from R occupancy (category 2) to A (occupancy (category 1).

Denver Energy Code Compliance

To comply with the Denver Energy Code, the project must comply with Section C505 Change of Occupancy or Use. The project has the option to comply with the energy code via the prescriptive pathway or one of the performance pathways, with certain exceptions under section C505.1:

Prescriptive:
- Change of occupancy must comply with the applicable requirements of sections C402, C405.2, C405.3 and C408
Performance:
- Follow C407 OR Appendix SE plus mandatory requirements

Exceptions to C505.1:

If the change of occupancy will not result in an increase in demand for fossil fuel and electrical energy, provide the calculations in the permit submittal and the space must comply with the requirements of the Denver Energy Code for alterations section 503
If the project team provides COMcheck calculations in the permit submittal showing that the proposed UA using the component performance alternative of the prescriptive path (section C402.1.5), is within 10% of the target UA, it does not need to comply with C505.1
If the space complies with C407.1.2, it does not need to comply with C505.1
If the space is less than 5,000 sf, it does not need to comply with C505.1

Green Buildings Ordinance Compliance

Because the building is less than 25,000 sq. ft. and there is no roof work, compliance with the Green Buildings Ordinance is NOT required.

2022 Denver Green Code Compliance

The project meets the definition of a “major renovation, commercial” because it is assumed to be a level 3 alteration for purposes of this example. It must comply with the limited mandatory use provisions of the 2022 Denver Green Code per section 101.4.1 for Limited Mandatory Use.

Energize Denver Compliance

Because the building is between 5,000 sf and 24,999 sq. ft., it must comply with Energize Denver prescriptive performance requirements for buildings of that size. Since the project scope includes lighting replacement, we recommend that the project team use this project as an opportunity to comply with the LED lighting requirement laid out in the Energize Denver Ordinance.