ULEB Energy Modeling for NYC Buildings


What is NYC ULEB (Ultra Low Energy Buildings)?

Ultra Low Energy Buildings (ULEB) represent NYC's progressive approach to incentivizing high-performance construction through the NYC Zoning Resolution. Introduced as part of the city's broader climate initiatives, the ULEB program rewards developers who exceed minimum energy code requirements with additional development rights—offering up to 5% more Floor Area Ratio.

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The ULEB Incentive: 5% Additional FAR

The cornerstone of the ULEB program is its zoning incentive. Projects that meet ULEB requirements can earn up to 5% additional Floor Area Ratio (FAR), which translates directly to more buildable square footage and increased project value. For a large development, this bonus can represent millions of dollars in additional revenue, making high-performance design not just environmentally responsible but financially advantageous.
This FAR bonus is available for new construction projects that demonstrate exceptional energy performance through comprehensive energy modeling and meet full electrification requirements consistent with Local Law 154 of 2021.

Key ULEB Requirements
  • Minimum Energy Savings Projects must demonstrate at least 15% better energy performance than the code baseline. This performance improvement must be calculated using an approved NYC Energy Conservation Code modeling method—specifically ASHRAE 90.1 Appendix G Performance Rating Method or Section 11 Energy Cost Budget Method.
  • Full Electrification ULEB compliance requires full building electrification consistent with Local Law 154 of 2021, prohibiting on-site fossil fuel combustion for heating, hot water, and other building systems (with specific exemptions for certain building types and applications).
  • Comprehensive Energy Modeling Unlike standard energy code compliance that focuses only on regulated loads, ULEB requires modeling of both regulated and non-regulated end-uses. For residential buildings, this includes tenant-installed lighting, cooking appliances, and elevators. For commercial office buildings, food service equipment and elevator systems must be included in the energy model.
  • Scope of Application The 5% floor area incentive is available for new ultra low energy buildings, and for existing buildings that retrofit to become fully electric, typically buildings over 25,000 square feet, though specific thresholds may vary based on project type and zoning district.

NYC Energy Conservation Code Compliance Methods

ULEB modeling must follow NYC's approved energy modeling protocols based on the 2025 NYC Energy Conservation Code (NYCECC), which is based on the 2024 IECC. Its commercial path is the 2025 NYC ASHRAE 90.1, ASHRAE 90.1-2022 with NYC amendments, enforced for applications filed on or after March 30, 2026.

ASHRAE 90.1 Appendix G Performance Rating Method

The Appendix G Performance Rating Method is the most commonly used approach for ULEB compliance. This whole-building performance simulation methodology compares a proposed building design against a code-compliant baseline building:

  • Baseline Building Model Constructed per ASHRAE 90.1 requirements, representing a code-minimum building with the same geometry, occupancy, and schedules as the proposed design
  • Proposed Building Model Represents the actual high-performance design with all efficiency improvements
  • Performance Metric The proposed building's site energy use intensity (EUI), including regulated and unregulated loads, must be at least 15% lower than the baseline

Approved Modeling Software
NYC accepts energy modeling programs developed by the U.S. Department of Energy, including:
  • DOE-2 (DOE-2.1E, DOE-2.2, DOE-2.3)
  • EnergyPlus
  • eQUEST
  • EnergyPlus-based tools such as OpenStudio

Other software must be approved by both the New York State Secretary of State and the NYC Department of Buildings Commissioner.

How to Approach ULEB Energy Modeling

Successfully achieving ULEB compliance and earning the 5% FAR bonus requires strategic planning from conceptual design through construction documentation. Our comprehensive approach ensures your project meets all requirements while maximizing the financial value of the zoning incentive.

Early-Stage Integration

We start modeling before the design is fixed:

  • Pre-Design Feasibility Analysis Before committing to pursue ULEB, we evaluate your project's feasibility for achieving the required 15% energy savings. This preliminary analysis examines building program, site constraints, and budget parameters to determine if ULEB is a viable and cost-effective path.
  • Conceptual Design Modeling Energy modeling should begin during schematic design to inform fundamental decisions about building orientation, massing, glazing ratios, and system types. Early modeling identifies the most cost-effective paths to achieve 15% savings before major design commitments are made.
  • FAR Bonus Optimization We help you understand the financial value of the additional 5% FAR and develop efficiency strategies that maximize ROI on your sustainability investments.

Comprehensive Building Envelope Strategies
  • Enhanced Thermal Performance Achieving 15% savings typically requires envelope performance significantly better than code minimum. We model various insulation strategies, high-performance window assemblies, and advanced glazing systems to minimize heating and cooling loads.
  • Thermal Bridge Mitigation Critical to ULEB success is addressing thermal bridging at slab edges, balconies, parapets, and window interfaces. Our detailed modeling quantifies thermal bridge impacts and helps design teams implement continuous insulation and thermally broken assemblies.
  • Envelope-First Approach By maximizing envelope performance, we reduce HVAC system sizes and costs, often making the incremental envelope investment cost-neutral or positive when considering reduced mechanical equipment.

High-Efficiency HVAC System Design
  • All-Electric Heat Pump Systems With Local Law 154's electrification requirements, ULEB projects must utilize electric heating systems. We model high-efficiency heat pump technologies including:
    • Variable refrigerant flow (VRF) systems
    • Air-source and water-source heat pumps
    • Ground-source heat pump systems
    • High-efficiency heat pump water heaters (COP 3.5+)
  • Energy Recovery and Ventilation We evaluate energy recovery ventilation (ERV) systems with effectiveness exceeding 75%, which can significantly reduce heating and cooling loads while maintaining excellent indoor air quality.
  • Part-Load Optimization Our modeling captures real-world part-load performance and includes strategies for optimizing fan energy consumption, critical for achieving the 15% threshold.

Lighting and Plug Load Strategies
  • Reduced Lighting Power Density We model lighting systems with power densities below code requirements, incorporating LED technology, daylighting controls, automated blinds, and advanced lighting controls.
  • Receptacle and Equipment Control For commercial buildings, we evaluate receptacle control strategies and efficient equipment specifications that contribute to the overall 15% energy savings target. A critical distinction in ULEB modeling is the comprehensive treatment of both regulated and non-regulated loads:
    • Regulated Loads (covered by ASHRAE 90.1 Sections 5-10):
      • HVAC systems
      • Service hot water
      • Interior and exterior lighting
      • Vertical transportation (elevators/escalators)
      • Transformers and motors
    • Unregulated Loads (not covered by standard energy code):
      • Tenant-installed cooking equipment
      • Tenant lighting in residential units
      • Plug loads and appliances
      • Process equipment
    • ULEB modeling must include realistic assumptions for all these end-uses to accurately calculate the 15% savings threshold.

On-Site Renewable Energy

Solar PV Integration While on-site renewable generation can contribute to overall building performance, projects must achieve the 15% savings primarily through efficiency measures. We model rooftop and façade-integrated solar systems to optimize their contribution within ULEB calculation methodologies.
Renewable Energy Credits Our analysis helps clients understand how on-site renewables interact with both ULEB requirements and Local Law 97 compliance strategies.

ULEB Compliance Documentation

Our energy modeling services include all documentation required for NYC Department of Buildings review and ULEB FAR bonus approval:

  • Energy Modeling Report Comprehensive documentation using DOB-approved forms (EN1 or equivalent) that includes:
    • Baseline building model characteristics
    • Proposed building model characteristics
    • Energy or energy cost comparisons demonstrating 15% or greater savings
    • Modeling assumptions and inputs
    • Quality control documentation
  • Construction Documents All energy-related design features shown in the energy model must be clearly identified in the construction drawing set, including:
    • Envelope assemblies with U-factors and R-values
    • Window specifications and performance values
    • HVAC system types and efficiencies
    • Lighting power densities
    • Service hot water system specifications
  • Modeling Files Electronic modeling input and output files must be available to the Department upon request for verification.
  • Electrification Documentation Proof of compliance with Local Law 154 electrification requirements.

Why Choose InversEnergy for ULEB Modeling

  • NYSERDA Qualified Primary Energy Consultant InversEnergy is a qualified Primary Energy Consultant under NYSERDA's RFP 3771, demonstrating our recognized expertise in energy modeling and building performance analysis at the highest levels of New York State standards.
  • Proven ULEB Success We have successfully guided numerous projects through ULEB approval, achieving the 15% savings threshold and securing the 5% FAR bonus for our clients.
  • NYC Regulatory Expertise Deep knowledge of NYC Energy Conservation Code, ASHRAE 90.1 Appendix G methodology, Local Law 154 electrification requirements, and DOB submission procedures ensures smooth approvals.
  • Financial Optimization We understand that the 5% FAR bonus represents significant financial value. Our approach balances efficiency investments with the economic return from additional developable area.
  • Early Involvement By engaging us during conceptual design, projects achieve better outcomes with lower costs. Early modeling identifies the most cost-effective path to 15% savings before expensive design changes become necessary.
  • Advanced Modeling Capabilities We utilize DOE2-based and EnergyPlus modeling platforms approved by NYC DOB, with extensive experience in complex envelope assemblies, thermal bridging analysis, and all-electric HVAC system modeling.
  • Integrated Design Support We work collaboratively with your design team, providing actionable insights that improve performance, constructability, and occupant comfort while achieving ULEB compliance.

Get Started with Your ULEB Project

Earning NYC's Ultra Low Energy Building 5% FAR bonus requires expertise, early planning, and strategic design integration. The additional development rights can significantly increase your project's value while contributing to New York City's climate goals.

Contact InversEnergy to discuss how our energy modeling services can help your project achieve ULEB compliance, earn the 5% FAR bonus, and position your building for long-term sustainability and regulatory compliance.

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