Strategic Decarb 101

The Role of Design Charrettes in Building Decarbonization Planning

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As the world grapples with the urgent need to reduce greenhouse gas emissions, the built environment has become a critical focus area to deliver progress. Buildings are significant contributors to global carbon emissions, and transitioning to more sustainable, low-carbon operations is essential for meeting climate goals. Planning for that transition now, through a thoughtful and rational approach, is key to achieving success over time.  

Design charrettes are an important tool project teams can use to support their decarbonization planning work. These collaborative design review workshops bring together diverse stakeholders to develop and refine strategies for reducing carbon emissions from buildings over time.  

What is a Design Charrette?

A design charrette is an intensive, multi-disciplinary workshop aimed at finding and refining solutions to complex problems. The term originated in 19th century Paris and refers to the practice of design students working intensely on their projects until the last minute, when a cart or “charrette” would be wheeled around to collect their final designs. The term has evolved to describe collaborative sessions that bring together developers, designers, domain experts, community members, and an array of other stakeholders to reach mutually beneficial outcomes. In the context of building decarbonization, design charrettes facilitate the rapid development of actionable (and at times substantially more innovative) strategies to reduce emissions from buildings, with alignment among multiple interested parties.  

Why Use Design Charrettes to Achieve Resource Efficient Decarbonization?

  1. Collaborative Problem-Solving: Building decarbonization requires input from a wide range of experts, including architects, engineers, asset managers, environmental scientists, and community leaders. A design charrette brings these diverse voices together in a collaborative setting, ensuring that all perspectives are considered. 
  2. Intensive Focus: The concentrated nature of a charrette allows participants to delve deeply into the problem at hand. Over several hours (or days), stakeholders can explore various scenarios, analyze data, and develop detailed plans that might otherwise take months to create using traditional methods. 
  3. Iterative Process: Charrettes are designed to be iterative, with multiple rounds of feedback and refinement as needed. This approach ensures that the final outcomes are well-vetted and robust, with broad support from all stakeholders. 
  4. Creative Solutions: The collaborative and open nature of charrettes fosters creativity and challenges deeply held assumptions about how to approach a problem by the charrette participants.  Participants are encouraged to think outside the box and develop innovative solutions that might not emerge in a more conventional planning process. 
  5.  Achieving Resource Efficient Decarbonization (RED): Charrettes enable stakeholders to develop highly strategic plans to transition a building away from on-site fossil fuel over time in a way that does not diminish high-performance operations, contains operating and capital expenses, and maintains a complex urban systems perspective including considerations relating to infrastructure and natural resources.

The Design Charrette Process

Charrettes are conducted just after a decarbonization concept plan is created and initial decarbonization measures are framed. A successful charrette requires being prepared to discuss the existing conditions of the building in detail, various decarbonization measures and approaches considered, and an understanding of the social and market conditions influencing the building owner’s decision making. The charrette process includes: 

  1. Preparation: Successful charrettes require careful preparation. This includes identifying key stakeholders and inviting them to join, gathering relevant data, and setting clear objectives for the workshop.  
  2. Workshop Session: During the charrette, the project team presents their building existing conditions and decarbonization approaches and engage in brainstorming, design review, and business discussions with a team of technical experts and industry leaders.
  3. Iteration and Feedback: Ideas generated during the sessions can be reviewed and refined through multiple rounds of feedback and additional charrettes as needed. This iterative process helps to improve and perfect the proposed solutions. 
  4. Implementation and Follow-Up: The final step is to translate the charrette outcomes into a formal strategic decarbonization plan and business case that leads to real-world actions. This may involve further planning, securing funding, and ongoing community engagement. 

Design charrettes are a powerful tool for addressing complex decarbonization challenges, especially in the planning and early implementation phase. With collaboration, creativity, and iteration, charrettes enable the development of effective and sustainable strategies to reduce carbon emissions from buildings.

Want to review your decarbonization plan with our team of experts?

Request a design charrette.

Assessment Tools

Strategic Decarbonization Assessment (SDA) Tool

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Insights from the Empire Building Challenge

The Strategic Decarbonization Assessment calculator is a valuable tool that allows building owners and retrofit teams to align their asset decarbonization strategies with their capital investment strategies. The SDA is designed to integrate assessment of multiple requirements including optimizing net present value, replacing equipment close to end of life, avoiding compliance fees, and coordinating electrification of fossil fuel equipment with future electric grid decarbonization. 

The SDA is a long-term financial planning tool for building owners to manage carbon emissions and energy use. During the Empire Building Challenge program, the tool guided participants in refining their decarbonization scenarios and identifying the most cost-effective decarbonization plans. Several teams were able to show positive net present value for their decarbonization plans compared to business as usual. This process can benefit many buildings and property owners in New York in better quantifying, representing, and identifying optimal decarbonization scenarios.

The SDA tool was built by Arup and Ember Strategies. It was previously developed for the San Francisco Department of the Environment and modified for NYSERDA use in the Empire Building Challenge.

Download SDA Overview

User Advisory

The SDA tool was created as the one-stop shop for the development and modeling of the business case that supports initiating a decarbonization roadmap. The SDA tool below was developed based on ASHRAE Standard 211 normative forms with a variety of users and use cases across the United States in mind. 

The tables and charts on the “Summary (Print Me)” tab outline assumptions, costs, savings, decarbonization trajectory and alignment with NYC’s LL97 requirements. The bar charts and trajectories on this tab should be a graphical representation of the narrative explanation of your plan and business case from the “Narrative & Measures” and “Alternatives” tabs. The “Carbon emissions per year, before offsets” and the “Relative NPV of Alternatives” charts on the “Summary (Print Me)” tab should illustrate the sequencing and timing of equipment replacement, relationships between ECMs and savings/costs.

SDA Inputs Table

The table below describes inputs of the SDA tool and directions associated with each.

On the “Building info and assumptions” tab, users input basic information about the building: floor areas, space types, fuel types and consumption (bill) data. The “Building info and assumptions” tab enables users to communicate building information in a highly customized way at a very granular level. Default values do not need to be changed unless the business case is materially impacted by these estimates (i.e.  maintenance costs are reducing in addition to energy costs). Most of these assumptions are found in the “Real Estate Characteristics” drop down menu. Use the drop-down menu to change the default escalations rates for general costs and specific fuel costs over time. Sensitivity analyses that explore a variety of future rate scenarios are encouraged to show that you have considered the sensitivity/fragility/resilience of your plan in a variety of futures. 

The “Regulatory Assumptions” drop down on this tab includes NYSERDA default values for fuel specific emissions factors stipulated by LL97. This section also automatically calculates the building’s LL97 emissions limits for the 2024-2029 and 2030-2034 time periods using building typology and GSF inputs on the same tab. Please note: As of 2024, the SDA tool has not been updated to reflect any recent changes to LL97 building classes and missions factors.

On the “Equipment Inventory” tab, users will input major energy using equipment. All the fossil fuel equipment and at least 80% of total energy using equipment should be inventoried and reported on this tab. Very similar or identical equipment can be grouped into one row (e.g. multiple AHUs of generally the same size and age). The date of installation is required as it determines the equipment life and is used to define the Business As Usual (BAU) trajectory – existing equipment is projected to continue functioning until it reaches End of Useful Life and is replaced, like for like, at that time. User-input costs for the like for like replacement are also required inputs to complete the BAU trajectory. Please note, the estimated replacement cost and year installed are required inputs for the SDA graphics. Replacement costs for decarbonization measures and BAU equipment replacement need not be overly precise – these cost numbers should be realistic to ensure ROI and NPV calculations are sufficient for comparative purposes.

NPV and savings calculations in the SDA are significantly influenced by major energy using equipment. To streamline SDA development and simplify analysis, project teams should focus on major equipment and group minor equipment together by age, if feasible. If you are not using the landlord/tenant cost/benefit breakout, keep all equipment in column I (Tenants Own/Operate) marked “No”. This tab also enables a simple summer/winter peak/off peak calculator for demand ECMs, but using this feature is optional and is not a replacement for a full 8760 hour model. 

The “Percent energy/carbon by equipment RUL” graphics to the right (cell AY) should populate as expected if everything is input correctly. This visual is often used in business case narratives, but does not appear on the Summary tab.

On the “Narrative & Measures” tab, users narratively define their alternatives and input all the ECMs (costs and energy/carbon impacts) that will be assigned to years on the “Alternatives” tab. The SDA automatically generates two BAU cases: one in which LL97 compliance is not sought and fines are applied, and one in which LL97 compliance is achieved through carbon offsets alone.

Note the measure life column is a critical input as it determines how long the measure’s savings will persist – if the measure ends without replacement, the corresponding uptick in energy/carbon on that year will show in the trajectory graphs. 

Some potential users may be generating detailed energy models and bringing the outputs from those models into the SDA. These users may streamline ECMs to minimize data entry and rely on the narrative explanation of the measures. The simplest ECM list in this case may be “Year 1 ECMs”, “Year 2 ECMs”, etc. with corresponding costs and benefits; but be advised that users must explain their measures very clearly where they have aggregated costs and benefits.

On the “Alternatives” tab, users schedule ECMs and review the bar charts and trajectories between those Alternatives. The charts on this tab should illustrate the business case consistent with the narrative section. As stated before, the landlord vs. tenant breakdown for ECMs is not required (column H of Alternatives) and the subsequent charts can be disregarded if not used. Note the Holding period and Analysis periods can be varied independently, but most EBC users keep both set for 20 years.

The “Total Relative NPV Compared to Baseline – Varying Time Horizons” chart (cell AZ) is very commonly used in internal business cases to evaluate cost-effectiveness of the Alternatives over different time horizons, but it is not included on the Summary tab.

Most of the calculations happen on the “Operating Statements” tab, where an annual operating statement is created for each alternative/baseline for the 20-year analysis period. Users can review these statements as needed; however, it is not recommended to edit this portion of the tool directly. This is typically done when troubleshooting a trajectory chart that does not match user expectations.

Download

The SDA tool is available for download below, including a blank version as well as a version with data from a sample building.

Blank SDA Sample Building SDA

Instructional Videos

Four instructional videos detailing each step of the SDA process are linked below:

Part 1: Introduction & Inputs

Part 2: Equipment Inventory

Part 3: Narrative & Measures

Part 4: Scenarios & Results

Engineering Solutions

Building Discovery

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Insights from Empire Building Challenge 

The discovery phase is intended to provide an initial understanding of the building’s existing conditions, current challenges, and potential opportunities. The data and insights gathered during this phase will be used to create the building’s calibrated energy model.  Key activities in this workstream include: 

  • Collecting and reviewing relevant building information 
  • Observing building operations under different conditions 
  • Testing subsystems and their interactions 
  • Creating the Business-as-Usual (BAU) base case 

This workstream is critical because it grounds the project team in the reality of the building’s current performance. It also helps build a jointly owned process for uncovering early energy or carbon reduction opportunities that can increase trust and enthusiasm to identify more complex measures as the project progresses.

At the end of this phase, the team should have a clear understanding of the building energy systems, its historical energy and carbon profile, the potential impact of local laws or other building requirements, opportunities for additional metering, and preliminary energy and carbon reduction opportunities. 

This workstream provides vital information on current challenges, near and longer-term carbon reduction opportunities, and the accuracy of the energy model. It also creates early wins that build momentum and trust. Getting the most out of this work requires trust-based collaboration between multiple stakeholders, including facilities managers, operations staff, the energy modeler, external contractors, and design engineers. Engaging with tenants to get insight into what drives their loads can also add value and inform this process. Data and insights on the building’s existing condition typically arise from four sources: 

  • Design documents 
  • Data from metered systems 
  • Direct observation and testing 
  • Building operations team feedback 

Each source is important, but it is the integration across these four categories of data that leads to deep operational insights and identification of major areas of opportunity. 

Inputs
  • Cross-disciplinary, trust-based collaboration
  • Tenant insights
Activities

Gather Information:
In this phase, project teams should work with the building management and operations teams to collect key information using the sample checklist shown below.

Survey the Building:
Understanding a building’s existing conditions requires time on-site. Design drawings, operator interviews, and utility data all provide valuable insight, but do not capture the nuances of how the building runs day-in and day-out. Project teams should plan to conduct an initial site walkthrough to confirm high-level information about the building equipment, systems, and operations strategies shortly after project kickoff. As the study unfolds, additional site visits to verify information, gain additional clarity on certain conditions, or evaluate the feasibility of implementing ECMs will be necessary. The more time the project team spends in the building, the easier it will be to capture the building’s existing conditions in the building energy model and to develop ECMs that are feasible. When completing the building walkthrough, the project team should evaluate the following: 

  • Space temperatures: does the space temperature feel too low or too high?
  • Infiltration conditions: are there noticeable drafts within the space?  
  • Pipe trim and valving: is there proper instrumentation within the system?  
  • Unoccupied space conditions: is equipment running when it should be off?  
  • Central plant operations: is equipment running more often than it needs to be? 
  • Piping/duct conditions: are there noticeable leaks or inefficiencies within the distribution?  
  • Multiple controls for different equipment within a single space or physically grouped thermostats: is it possible that the controls are causing conflicting operation?  

Deploy Additional Metering (if required):
Collecting documentation and surveying the building will highlight gaps in data or information needed to build a calibrated energy model. To fill these gaps, the project team may elect to deploy additional metering to capture the missing information. Metering ultimately reduces speculation and provides real-time insight into the building’s operations. Project teams should execute the following steps when developing a metering strategy: 

  • Identify and create an inventory of existing meters, submeters and instrumentation. 
  • Verify the accuracy of existing meters and ensure they are properly connected and integrated in the building management system (BMS). 
  • Gain direct access to view the BMS data. Ideally, the team will have viewing access to real-time building operations during the entire duration of the project. 
  • Identify areas where additional meters will be required. 
  • Develop a deployment program for additional metering needs including preferred vendors, meter types, meter quantities, locations for placement, and an installation schedule. 

Observe and Test Systems:
Building system assessments and functional tests are great ways to capture operating parameters, evaluate performance, and identify issues that can be resolved with retro-commissioning. Project teams should conduct some or all the following building tests to further inform the study:

Test/AssessmentGoalsReference/Procedure
Building envelope performance and infiltrationUnderstand the conduction losses/gains through the envelope. This will inform potential envelope opportunities and the baseline energy model.Refer to ASTM E1186 – 17 for standard practices for air leakage site detection in building envelopes and air barrier systems. 
Tenant electric load disaggregation, i.e. plug loads, lighting, ITIdentify high consumption loads within tenant spaces to target critical loads and opportunities.Select one or two tenants and install submeters on their floor (can be temporary), separating out loads by lighting, IT, plug loads. Analyze consumption and data trends to develop energy conservation measures.
Setpoints and setbacks in all spaces (tenant areas, common area, IT rooms, MEP) during winter and summer seasonsDetermine the most energy efficient setpoint/setback while maintaining a comfortable space. Evaluate what is possible within each space. Evaluate the ability of the system to recover from the setback without causing excessive utility demand.Test potential setpoint and setback temperatures within each space type to determine the optimal energy efficient condition.
Airside controlsVerify that airside controls are configured to optimize energy and indoor air quality.  Identify easy-to-implement and inexpensive controls ECMs.Test procedures will vary based upon the type of airside equipment in use; however, the following assessments are applicable to many airside configurations and can act as a starting point: 
Step 1: Verify that static pressure setpoint controls are correct per the sequence of operations or current facility requirements.  
Step 2: Verify that supply air temperature resets are programmed and operating within the correct range.  
Step 3: Verify that terminal box minimum and maximum setpoint are appropriately set per the latest balancing report. 
Step 5: Confirm if outdoor airflow stations are installed, and if so, verify that the appropriate amount of outside air is being delivered per the design documents or current facility requirements.  
Step 6: Verify if a demand control ventilation (DCV) program is in place. If so, confirm that outside airflows are reduced as occupancy is reduced. 
Step 7: Verify that turndown controls are appropriately reducing equipment temperatures or flows in low load conditions.
Waterside controlsVerify that waterside controls are configured to optimize energy and are load-dependent.  

Identify easy-to-implement and inexpensive controls ECMs.

Test procedures will vary based upon the type of waterside equipment in use; however, the following assessments are applicable to many waterside configurations and can act as a starting point:  
Step 1: Verify that static pressure setpoint controls are correct per the sequence of operations or current facility requirements.  
Step 2: Verify that supply or return temperature resets are programmed and operating within the correct range.  
Step 3: Confirm if an economizer mode is available, and if so, verify that the system appropriately enables this mode in certain weather conditions.  
Step 4: Verify that turndown controls are appropriately reducing equipment temperatures or flows in low load conditions.
BMS anomalies and faultsIdentify discrepancies in what the BMS is outputting on the front-end versus the actual observed conditions. Identify easy-to-implement and inexpensive controls ECMs.For each tested system, compare the BMS outputs to the actual measured data or observed condition. Identify the root cause of the discrepancy and resolve.
Outputs
  • An additional metering strategy with a timeline for installation and a plan for measurement & verification of new meters.  
  • A preliminary list of operational adjustments and retro-commissioning issues based upon building surveys and building system assessment/tests. 
  • A plan for implementing operational opportunities like setbacks and setpoint adjustments.

Lessons Learned and Key Considerations

Business operations are as important as facility operations:
Energy studies tend to focus only on the architectural and MEP operations within the building. Project teams spend a lot of time understanding how equipment and systems operate and perform, but often don’t spend enough time considering the building’s existing lease turnover schedules, existing capital plans, or hold strategy. These business considerations are critical to understanding the types of decarbonization strategies that building ownership are likely to invest in.

2. Build the “Business-as-Usual” Base Case

Building the business-as-usual (BAU) base case occurs between the Discovery and Energy Modeling phases and includes an analysis of the building’s utility data to gain insight into how the building uses energy at a high level and how that consumption translates to carbon emissions. From this analysis, the project team will be able to evaluate the building’s exposure to mandates such as Local Law 97. 

Inputs

Building the BAU base case requires obtaining one full year of utility data, at a minimum.

Activities

Utility Analysis (Baseline Condition):
As the project team learns the building, one full year of utility data (at a minimum) will be collected. The project team should visualize this data monthly to further develop its understanding of how and when the building uses energy. The following list of questions can be used to guide the analysis: 

  • What fuel types are consumed by the building? 
  • When are fuel types used the most or the least and why? 
  • Are there unexpected usage peaks for certain fuel types? 
  • What is the building Energy Use Intensity (EUI) and how does it compare to peer buildings? 
  • What is the building Energy Cost Intensity (ECI) and how does it compare to buildings? 
  • What service class is the building in and what is the tariff structure for that service class? 
  • How does demand correlate with cost?  

Based on the results of this activity, the project team will begin to form hypotheses about how building systems interact, which end uses are the most energy intensive, and where deeper energy and carbon reduction strategies may be pursued.  

Building Performance Standard Impact Analysis:
Depending on the jurisdiction in which the deep energy retrofit study is taking place, it may be beneficial for the project team to evaluate the building’s current performance against mandates or building performance standards (BPS) that are in effect. In New York City, for example, Local Law 97 is a BPS that many building owners are focused on. Other jurisdictions may have energy use intensity (EUI) targets or other metrics for performance. The outcome of the impact analysis may help to inform the overall decarbonization approach for the building. Project teams should execute the following steps to conduct a BPS impact analysis: 

  • Step 1: Aggregate annual utility data by fuel type. 
  • Step 2: Convert raw data into the appropriate BPS metric. In the example of LL97, annual fuel consumption is converted to annual carbon emissions with carbon coefficients that are published in the law.  
  • Step 3: Compare the building’s annual performance against the BPS performance criteria. 
  • Step 4: Consider how the building’s performance might change over time as the electric grid decarbonizes. In the example of LL97, a building’s carbon emissions associated with electricity consumption will naturally decline over time as the grid decarbonizes. 
  • Step 5: Calculate impacts of compliance or non-compliance with the BPS. For LL97, building emissions in excess of the allowable carbon limit results in an annual financial penalty.   
  • Step 6: Share results with the building management and ownership teams to further inform that building decarbonization approach.

During the energy retrofit process, the team will discover simple ways to reduce energy consumption that can be implemented almost immediately. With real-time data, the BMS allows the team to analyze how effective the changes to the system are.

Outputs

Deliverables for this task include the following: 

  • Energy, carbon & cost end use breakdowns (monthly) 
  • Demand and tariff structure analysis 
  • Mandate or Building Performance Standard impact analysis

Lessons Learned and Key Considerations

3. Identify Preliminary ECMs and Carbon Reduction Strategies

Inputs

Based on the work completed during the “Learn the Building” and “Build the BAU Base Case” tasks, the project team should already have a sense of the ECMs that are a good fit for the building. The project team should review the outcomes of the work done up to this point and develop a list of preliminary strategies so the team can level set on an approach as the project enters the Energy & Carbon Modeling phase.  

Activities

• Develop a Tiered List of ECMs:
Through the document collection and building system assessments, the project team likely identified low or no-cost operational items that can be implemented immediately. These simple items should be grouped and presented as Tier 1 measures. Deeper measures that require more upfront capital and/or have a longer lead time should be separated out into Tier 2 items. Tiers can be based upon cost or timeframe for implementation. Categorizing measures in this way will support building owner decision-making. 

• Conduct a Qualitative Assessment of ECMs:
Once the measures are appropriately categorized into tiers, the project team should generate a qualitative assessment of each measure, based on metrics that are important to the building management team. For example, one building team may identify disruption to tenants as their primary go/no-go metric when deciding which strategies deserve deeper analysis. Metrics will vary from project to project. 

• Present and Solicit Feedback:
Present the tiered list of ECMs, along with the qualitative assessment, and solicit feedback from the building management team. Eliminate ideas that don’t meet the team’s decarbonization approach and welcome new items that the building team may want to pursue that were not originally considered. This process will bolster team engagement and ensure that time spent in the energy model is dedicated to measures that will be considered seriously by the building team for implementation.

Outputs

The output of this task will be a finalized list of energy reduction strategies to study the next phase: the Energy & Carbon Modeling Phase.

Lessons Learned and Key Considerations

Strategic Decarb 101

About Resource Efficient Decarbonization

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Insights from Empire Building Challenge

Improved engineering design means and methods are needed to enable and speed adoption of low-carbon retrofit technologies. High performance, low-carbon heating and cooling systems are widely available but are underutilized in the United States due to a variety of misconceptions and a lack of knowledge around thermal system interactions. Few practicing engineers prioritize recycling heat and limiting heat loss. Decarbonization requires upgrading and adapting energy distribution systems originally designed to operate with high temperature combustion to integrate with electric and renewable thermal energy systems. The engineering design industry can use a thinking framework like Resource Efficient Decarbonization (RED) to deliver projects that achieve more effective decarbonization.  

This framework emerges from the Empire Building Challenge through continued collaboration among real estate partners, industry-leading engineering consultants, and NYSERDA. RED is a strategy that can help alleviate space constraints, optimize peak thermal capacity, increase operational efficiencies, utilize waste heat, and reduce the need for oversized electric thermal energy systems, creating retrofit cost compression. While RED is tailored to tall buildings in cold-climate regions, the framework can be applied across a wide array of building types, vintages, and systems. The approach incorporates strategic capital planning, an integrated design process, and an incremental, network-oriented approach to deliver building heating, cooling, and ventilation that: 

  • Requires limited or no combustion,
  • Enables carbon neutrality,
  • Is highly efficient at low design temperatures and during extreme weather,
  • Is highly resilient, demand conscious, and energy grid-interactive,
  • Reduces thermal waste by capturing and recycling as many on-site or nearby thermal flows as possible, and
  • Incorporates realistic and flexible implementation strategies by optimizing and scheduling phase-in of low-carbon retrofits competing with business-as-usual.

Decarbonization Framework

Resource Efficient Decarbonization focuses on implementing enabling steps that retain a future optionality as technology and policy evolves. This framework allows a building owner or manager to take action now, instead of waiting for better technology and potentially renewing a fossil-fueled powered energy system for another life cycle.

The figure below illustrates a conceptual framework for accomplishing these objectives and overcoming the barriers. Specific measures and sequencing will be highly bespoke for a given building, but engineers and their owner clients can use this bucketed framework to place actionable projects in context of an overarching decarbonization roadmap.

Resource Efficient Engineering Steps

Step-by-Step Process to Advise Decarbonization Efforts

  1. Understanding a building’s fossil fuel use in detail is a critical first step. Make an effort to understand when, where, how, and why fossil fuels are being consumed at the building and under what outdoor temperature and weather conditions. Conduct a temperature BINS analysis to know how much fossil fuel is consumed during various temperature bands (typically in 5- or 10-degree increments) from design temperature up to the end of the heating season. Make an effort to understand cooling season usage patterns in detail. Go further and conduct an 8760 hour/year analysis or modeling effort to show building operation profiles with high granularity to advise targeted elimination of fossil fuel consumption.
  2. While electrification is desirable to combat climate change, energy efficiency is a  critical component of decarbonization. Reducing heating and cooling loads across all weather conditions is a major early step to achieve RED. 
  3. Identify the ways heat is being gained or lost. Hint: some places to look at are cooling towers, facades and windows, elevator machine rooms, through sewer connections, or at the ventilation exhaust system. Cooling towers operating in the winter are an obvious energy wasting activity. Seek solutions to reduce, recover, and recycle or reuse, and store this heat. 
  4. After, or in parallel with the previous steps, begin to electrify the building heat load, starting with marginal “shoulder season” loads (spring and fall). Don’t force electric heating technology such as air source heat pumps to operate during conditions for which they weren’t designed. Optimize heat pump implementation through a “right sizing” thermal dispatch approach to avoid poor project economics and higher operating expenses. This means continuing to retain an auxiliary heating source for more extreme weather conditions until fossil fuels are ready to be fully eliminated. This approach provides owners time to identify the right peak period heating solution while allowing them to act early in driving down emissions. Emissions reduced sooner are more valuable than emissions reduced in the future.
  5. Remove connections to fossil fuels and meet decarbonization deadlines!

Take Actions with these Enabling Steps

Review

  • Disaggregate time-of-use profiles to identify heat waste and recovery opportunities and to right-size equipment.
  • Thermal dispatch strategy: layering heat capacity to optimize carbon reduction and project economics.

Reduce

  • Repair, upgrade and refresh envelopes.
  • Optimize controls.

Reconfigure

  • Eliminate or reduce inefficient steam and forced air distribution.
  • Create thermal networks and enable heat recovery.
  • Lower supply temperatures to ranges of optimal heat pump performance.
  • Segregate and cascade supply temperatures based on end-use.

Recover

  • Simultaneous heating and cooling in different zones of building.
  • Eliminate “free cooling” economizer modes.
  • Exhaust heat recovery; absorbent air cleaning.
  • Building wastewater heat recovery.
  • Municipal wastewater heat recovery.
  • Steam condensate.
  • Refrigeration heat rejection.
  • Other opportunistic heat recovery and heat networking.

Store

  • Store rejected heat from daytime cooling for overnight heating.
  • Store generated heat— centrally, distributed, or in the building’s thermal inertia.
  • Deploy advanced urban geothermal and other district thermal networking solutions.

Building Systems Topologies

Commercial Office

Commercial office buildings offer significant heat recovery and storing opportunities due to simultaneous heating and cooling daily profiles. As a result, offices can heat themselves much of the year with heat recovery and storage. Example load profiles for typical heating and cooling days in a commercial office building are shown in the graph below.

Office heat and cooling load

Multi-family

Multi-family buildings’ typical daily profiles show efficiency opportunities that can lower and flatten system peaks. This can be achieved by a variety of heat reduction, recovery, and storing strategies​. Example load profiles for a typical heating day in a multifamily building are shown in the graph below.

Multifamily heat load

Thermal Distribution Opportunities

The thermal energy network approach enables transaction of thermal energy to increase overall system efficiency and reduce wasted heat. The concept can be applied at the building level (with floor-by-floor heat exchange), to groups of buildings, to whole neighborhoods, or to cities. Below is an illustration of a whole-system, thermal network approach applied in an urban environment to supply clean heat in cold-climate tall buildings:​

Resource Efficient Engineering Steps Exemplified

Engineering Solutions

Energy & Carbon Modeling Guide

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Insights from the Empire Building Challenge

A calibrated energy model should play a central role in building out a decarbonization plan because it provides insights on:

  • Current building energy and carbon profiles, and costs.
  • Potential energy, carbon, and cost savings of energy conservation measures (ECMs.
  • The impact of groups of ECMs, and the order of implementation and timeline.

The steps to follow include:

  • An initial energy model is developed using commonly available building information such as architectural floorplans, MEP schedule sheets, and BMS sequences of operation. 
  • The initial model is then refined and “calibrated” to the building’s real utility data for each utility consumed, creating a baseline condition that ECM’s will be compared against. 
  • The baseline energy model is used as a test bed for individual ECMs to understand potential energy, carbon, and cost impacts. 
  • Evaluate the financial performance of each ECM. These results will be used to identify strategies that are economically viable and should be considered further.  
  • Those ECMs that are economically viable on their own may be grouped together with other ECMs to help build a holistic business case for system optimization and maximum carbon reduction. 
  • During the evaluation process, the project team should take the evolving emission factors associated with utilities such as electricity and steam, as well as the impact of rising average and design day temperatures/humidity, into account.

Key outputs from the energy modeling workflow should include data driven charts showing energy end use breakdown and costs, carbon footprint of each utility, building carbon emissions vs. LL97 targets and fines, and who “owns” the carbon footprint (i.e. tenants, building operations). It is important to note that not all energy models are created equally. For a deep energy retrofit project, the accuracy of the energy model should align with ANSI/ASHRAE/IES Standard 90.1. Code or LEED energy models that were developed for the building in the past are not appropriate for this effort.  

Learn more about building energy modeling. 

Below is a selection of the energy modeling software packages used to support the case study findings presented in this Playbook, and throughout the industry.

1. Build and Calibrate the Initial Energy Model

An energy model is developed in multiple phases. In the first phase, the energy modeler must build an initial model that captures the geometry, material attributes, occupancy types, MEP systems and basic information about the building’s operations. The energy modeler should also include surrounding buildings that may impact sun exposure on the different facades of the building under study. This initial model will produce a rough estimate of how the building performs every hour during the year. Then in the next phase, the energy modeler must hone the model’s accuracy by “calibrating” the initial model to utility data and detailed building operations information. Code or LEED energy models that may have been created for the building during its initial design and construction should not be used in deep energy retrofit study efforts because they do not reflect the actual performance of the building under study.

Lessons Learned and Key Considerations

  • Determine energy model accuracy expectations early: Energy model accuracy can vary widely. For a deep energy retrofit study, the energy model should be highly accurate and align with ANSI/ASHRAE/IES Standard 90.1. Building management teams should set model accuracy expectations with the energy modeler at the onset of the project. This will help inform how assumptions are made and where the modeler should or should not simplify certain aspects of the model. 
  • Energy model calibration takes time but is worth the investment: Calibrating the initial energy model is a continuous and iterative process that can span multiple days or weeks depending on the complexity of the building. This time investment is well worth it because the quality of the energy modeling results is directly dependent on the quality of the calibration effort.  
  • Sync energy modeling assumptions with site observations: Even well-maintained buildings with stringent base-building and tenant standards have operational nuances and anomalies. Equipment may be shut off or sequences may be manually overwritten because the system wasn’t commissioned, wasn’t correctly integrated with the BMS, or was causing a localized issue that required a quick fix. This is especially true for older existing buildings that have had operations team turnover resulting in a loss of institutional knowledge over the years. For the energy model to accurately capture savings for ECMs, the calibrated model must reflect real-life operation. The project’s energy modeler should capture these nuances in the calibrated model whenever possible. 
  • Perfection is the enemy of “good enough”: The energy model will never perfectly simulate the performance of the building. There will also be a margin of error that comes from very specific nuances in building construction or operation that can’t be captured by simulation-based software. The project team should set reasonable expectations for the level of modeling and calibration effort that aligns with AANSI/ASHRAE/IES Standard 90.1 but also conforms to the project schedule and status. 
  • Share model visualization with the project team: Energy modeling can be a complex topic that may seem inaccessible to non-technical audiences. To maintain good project team engagement during the energy modeling phase, the energy modeler should prepare and share data visualizations that can help tell the story of how the building uses energy. Graphs, rendering, and infographics are great examples of visual assets that can demystify the energy modeling process.  

2. Create the Baseline Energy Model

The baseline model represents the current systems and operations of the building, adjusted for “typical” weather conditions and other criteria. Energy savings for all proposed ECMs will be calculated relative to the baseline model performance.

Inputs

  • The calibrated energy model 
  • TMY weather data 
  • List of planned upgrades, tenant lease turnover schedules

Activities

Make Necessary Adjustments to the Baseline Model: To create a baseline energy model, the calibrated energy model consumption should be adjusted to account for the following: 

  • Weather: Typical weather data for the site can be modeled using TMY3 data files, which capture and compare typical performance and eliminate any extreme weather event effects that may have occurred in the baseline year. TMY3 files are produced by the National Renewable Energy Laboratory and can be freely accessed and downloaded from the EnergyPlus website. 
  • Occupancy (Lease Turnover or COVID): The baseline energy model should be adjusted to account for any fluctuations in building occupancy that are expected to occur over the study period. For example, tenant lease turnover schedules should be collected during the Discovery Phase and accounted for in the baseline model. Similarly, any disruptions to building occupancy, such as those experienced during the COVID 19 global pandemic, should be captured in the baseline model. To understand the full magnitude of ECM impacts, it is important to separate energy reductions resulting from ECMs versus those resulting from lower occupancy levels. 
  • Planned Upgrades: The baseline model should be adjusted to account for any planned projects that will impact the building’s energy consumption. By capturing these savings in the baseline model, the project team will avoid projecting ECM savings that are no longer available because they have already been captured by planned projects.  

The baseline model represents “business as usual” building energy consumption and associated energy cost. It is the reference point used to determine the energy savings of potential ECMs and track progress towards reaching project objectives. 

Generate Detailed End-Use Breakdowns: Once the baseline energy model is complete, the project team can begin to gain additional insight into how the building uses energy. A particularly useful output of the model is a detailed end-use breakdown like the one shown below:

The energy modeler will be able to analyze this end use breakdown and identify systems that appear to be high energy consumers. Hypotheses should be vetted by the engineer and facilities team based on their understanding of the building.

Document Assumptions and Review Initial Results with the Team: After the initial baseline model has been built, the energy modeler should review his/her/their assumptions and the resulting load breakdowns with the project team. The modeler should then solicit feedback from the engineers and building operators who have greater insight into the current building operation and systems design. Feedback should be incorporated into the next iteration of the baseline model. The feedback loop between the energy modeler and the building team will be an iterative process that will continue throughout the duration of the project as more information is collected from the building. 

Overlay Carbon Emissions: Once the baseline energy consumption results are refined, the associated operational carbon emissions can be calculated by multiplying the annual energy consumption by a fuel-specific carbon coefficient. Carbon coefficients represent the greenhouse gas emissions intensity of different energy sources and are used to determine a building’s total greenhouse gas emissions in tons of CO2 equivalent. This analysis will identify the primary contributors to greenhouse gas emissions in terms of fuel type, system, and ownership (end-user that is driving the demand). 

Refine the Preliminary List of ECMs: At this point, the energy modeler and engineer should work together to refine the preliminary list ECMs that was developed in the “Build the BAU Base Case” task. The additional information gleaned from the detailed end use breakdown should be used to validate the initial list of measures and to identify new areas of focus that were not identified in early phases of the project.

Outputs

Deliverables from the baseline energy model work include the following: 

  • Baseline energy model is a reference for potential energy, carbon and cost savings   
  • Building energy consumption and detailed end use breakdowns 
  • Documented baseline system assumptions  
  • Finalized List of ECMs for study in the energy model

Lessons Learned And Key Considerations

  • Document and review input assumptions: A robust energy model can be a reusable tool that can serve the building team for many years after the initial deep energy retrofit study. To ensure the information within the model is accurate and up to date, any inputs and assumptions should be documented and shared with the building management team. This will give the team the opportunity to correct any assumptions that do not align with the actual operation of the building and will create a log where inputs can be revised and updated as the building evolves.

3. Analyze Individual ECMs

    In this task, the energy modeler will run all ECMs in the energy model and extract associated energy, carbon, and cost savings for each. For this task, the energy modeler will need the baseline energy model and the finalized list of ECMs that will be evaluated.

    Inputs

    For this task, the energy modeler will need the baseline energy model and the finalized list of ECMs that will be evaluated.  

    Activities  

    Develop a Modeling Strategy for Each Energy Conservation Measure (ECM): Before the modeler begins modeling each ECM, he/she/they should develop a modeling strategy for each measure including performance characteristics and any important assumptions. Documenting model inputs and modeling strategy for each ECM will make it easier to troubleshoot if there are any surprising results. 

    Run ECMs in the Model and Analyze Results: Once all ECMs are explicitly defined and the modeling strategy has been finalized, the modeler will run each ECM to create a proposed energy model. The proposed energy model is compared to the baseline energy model to estimate energy, carbon and cost savings. The energy modeler will extract savings for each ECM from the proposed model, which will enable the team to study the individual impact of each ECM and vet the results. Energy savings for individual ECMs should be compared to industry experience to gauge their validity. When surprising results arise, the team must explore why and either justify the inputs or modify them according to additional information. 

    Refine and Troubleshoot as Needed: Assumptions may need to be revised after this initial review of the results, especially if there are unexpected results.  

    Compare Mutually Exclusive ECMs: In some cases, the team may develop mutually exclusive ECMs. These competing ECMS must be compared to determine which is the most energy efficient and by what margin. The energy model can be used to run multiple ECM options and compare estimated energy savings between them. The project team should decide which mutually exclusive ECMs should be advanced into the future rounds of analysis before packaging ECM in the next phase of modeling. 

    Assess Maximum Theoretical Potential for Energy Savings: The final energy consumption of the proposed model will factor in all the energy savings associated with the ECMs. This resulting value is the theoretical minimum energy consumption for the building, assuming all technically viable ECMs are implemented. At this point it is helpful to determine the percent reduction from the baseline and evaluate how this theoretical minimum stacks up to the project objectives. Important questions to answer include:   

    • Does the theoretical minimum energy consumption meet or exceed the project’s energy and carbon goals, and if so by how much?    
    • Which ECMs contribute most significantly to energy and carbon reductions and are they likely to be financially feasible?   
    • Are most of the energy savings attributable to a few select ECMs or are energy savings spread evenly amongst many small measures?   

    The analysis of the energy modeling results can be facilitated by the creation of ECM waterfall charts which show the baseline energy consumption / carbon emissions and the progressive impact of each ECM on these values. The final energy consumption and carbon emission of the proposed model will establish the theoretical minimum.   

    Outputs

    Outputs and deliverables of this work include: 

    • Initial energy, carbon, and cost savings for individual ECMs. Based on this initial review and analysis, the team will identify further data collection required to refine the modeling assumptions and improve the accuracy of the outputs.  
    • Actionable information regarding which mutually exclusive ECMs are most impactful and should be advanced to the next phase of modeling. 
    • The maximum theoretical energy savings and carbon reduction for the building. This will give the project team an indication of how many ECMs may need to be implemented to meet the project objectives.  
    • Initial energy cost savings for each measure, which can be used to inform preliminary financial analyses.

    Lessons Learned & Key Considerations 

    Review and question surprising results: When reviewing preliminary energy savings, it is important to make sure that the results make sense and question any surprising results. The energy modeling results are only as accurate as the modeling inputs. These assumptions must be vetted to ensure accurate savings. Data collection during this time will be useful to determine modeling assumptions. Assumptions can also be informed by the insights and advice from industry experts. Energy modeling is an iterative process, and the model will continue to be refined as more information is collected.  

    Identify high priority ECMs: Preliminary results may indicate that most of the energy savings available are attributable to a select number of ECMs. Implementing these select few ECMs may be all that is required to meet the project’s short-term objectives. The project team should focus on refining the inputs for these high impact ECMs to ensure accurate savings.  

    Remember many small measures have a cumulative impact: To maximize savings and meet long-term project objectives like 80×50 it is likely that a wider array of ECMs will need to be considered for implementation. This holds true especially for buildings that have undergone recent renovations where the most impactful ECMs have already been executed. In this case it may be necessary to evaluate the cumulative impact of many small measures. Therefore, individual measures with minor carbon reduction impacts should not be dismissed too quickly.

    4. Group, Sequence, and Package ECMs

      As the Energy and Carbon Modeling phase is progressing, a preliminary financial analysis of individual ECMs will also take place in parallel. Preliminary results from the financial analysis will help inform this phase of modeling. Individual ECMs should not necessarily be discarded based solely on their associated capital cost; expensive ECMs can be grouped together with related financially viable measures to optimize savings and make a more comprehensive business case that maximizes CO2 reduction while still addressing investment return hurdles.   

      Once ECMs have been grouped, an implementation duration and timeline should be established for each. This will depend on factors like short term project budgets, tenant lease turnover, operational budgets, and maintenance schedules. The ECMs should then be sequenced according to their implementation timeline so that energy savings for each ECM can be captured accordingly.  

      Finally, several ECM packages should be assembled for owner evaluation. Each package will include a different combination of ECMs to be implemented with varying degrees of cost and carbon impact. This variety will provide the owner with options to choose from when striving to balance the project objectives and constraints.

      Inputs

      For this task the project team will need the following inputs: 

      • Energy, carbon & cost savings from the proposed energy model 
      • Preliminary ECM capital costs estimates: Preliminary results from the financial analysis will provide approximate NPV values for each ECM based on the projected energy cost savings and capital costs. These results will be used to identify those ECMs that are economically viable on their own, those that are worth pursuing due to large carbon impact, and those that should be discarded at this point due to technical infeasibility, cost, or low carbon impact. Those ECMs that are economically viable on their own may be grouped together with related, and costly, but effective, ECMs to help build a stronger business case.

      Outputs  

      Outputs and deliverables of this task include the following: 

      • Finalized grouped and sequenced ECM list.  
      • Results from Packaged ECMS for Owner consideration.

      Activities 

      Establish the Final List of ECMs: Once a preliminary financial analysis has been conducted and approximate NPV values and energy and reductions are calculated for each ECM, the list of measures should be reviewed and finalized. Typically, ECMs will fall into the 5 categories described below, with associated outcomes:  

      1. ECM has a positive NPV and has a large carbon impact. ECM should be considered seriously for implementation. Additional QA/QC should be completed to ensure savings are accurate. 
      2. ECMs that has a positive NPV but has a minor carbon impact. ECM should be evaluated collectively with other measures, as the impact of many small measures can compound. 
      3. ECM has a positive NPV and has a large carbon impact but is technically challenging or infeasible. ECM should likely be eliminated because it will not seriously be considered for implementation by the Owner or building operations team
      4. ECM has a negative NPV (simple payback may still be within the useful life of the ECM) but has a large carbon impact. Financial case for the ECM should be investigated further – the incorporation of maintenance costs, baseline requirements or planned capex unrelated to emissions reductions, and potential incentives in the financial model may improve the financial performance. 
      5. ECM has a negative NPV and a small carbon impact. ECM should be eliminated.

      Group and Sequence the ECMs: Once the list of ECMs has been finalized, the project team should determine the anticipated duration of time required for completion and the implementation sequence. There are various considerations that should be understood during this part of the modeling process: 

      • The timing of implementation will be unique to each building and vary depending on the types of existing systems and their age and performance. Well maintained systems may be able to be updated and optimized in the short term and replaced in the long run depending on the project objectives.   
      • The sequence of ECMs will depend on various factors including tenant lease turnover schedules, maintenance schedules, and investment cycles. 
      • Interrelated and codependent ECMs should have the same timeline and/or be sequenced appropriately. Some ECMs should be considered as a group to help make a financial case for optimized carbon reductions. 
      • The impact of the ECMs will decrease as the sequence progresses, and savings will be less than if they were directly compared to the initial baseline. This is because as each new ECM is executed and absorbed into the baseline model, this “new” baseline model against which new ECMs are compared performs more efficiently, thereby decreasing the potential for savings. 

      Create ECM Packages: Once the ECMs have been sequenced, various implementation packages should be compiled for final evaluation. Given that implementing all ECMs will likely be cost prohibitive, the project team should provide the owner with different options along the spectrum of project cost and carbon reduction.    

      To book end the problem, it is recommended that two of the proposed packages be a “CO2 Maximum Reduction” package and an “NPV Maximum” package. These packages are described below:

      • CO2 Maximum Reduction: Package includes all technically viable measures, even if they are not economically viable at the time of the analysis. The purpose of this package is to find the technical maximum CO2 reductions achievable.
      • NPV Maximum: Package includes only those measures that payback within the study period and have positive NPVs. These are the minimum CO2 reductions that can be expected with a financially viable package.

      Additional packages should be created and evaluated based on feedback from the project team. These hybrid packages will allow the owner to choose from a wide range of options with different value propositions.

      Lessons Learned & Key Considerations

      Visualize the results: A helpful tool for analyzing ECMs results is a 2 x 2 matrix that shows the NPV vs. the CO2 reductions for each ECM. 

      Consider non-energy benefits: Before eliminating measures because they have small carbon impacts, the project team should evaluate the non-energy benefits of the measure. If the non-energy benefits align with the owner’s overall sustainability strategy or make the building a more valuable asset, the building team may still wish to pursue the item. For example, a façade upgrade or replacement may not have a positive NVP but will make the building more competitive with newer buildings.  

      5. Generate a Decarbonization Roadmap

      Once the finalized ECMs have been grouped, sequenced, and packaged, the energy model can be run to obtain final results. These results will be used in the detailed financial analysis and will represent a time-dependent decarbonization roadmap for the building. The final results will include energy savings, energy cost, and CO2 reduction for each package under study, and should phased according to the anticipated implementation timeline to reflect the gradual and overlapping impacts of each measure over a 20- or 30-year time horizon.  CO2 reduction over a longer time horizon should include a changing electric grid carbon coefficient to account for grid decarbonization.

      Inputs

      The inputs for this task include: 

      • The finalized ECM Packages 
      • Carbon coefficients for the Future Grid 

      Activities

      Run Final ECM Packages in the Model and Analyze Results: The modeler should update the proposed model based on the final list of ECM packages and intended implementation sequence. Energy results should be provided for each ECM, even if there are several ECMs that are intended to be grouped together, as this provides granular data for the financial analysis to be conducted down the line. This is important because each ECM may have distinct capital costs, maintenance costs, and incentive implications which may impact the financial viability of the measure.     

      To reduce the modeling time, it may be assumed that a given ECM’s savings are recognized at once, even if it is anticipated that the ECM and associated savings will be realized over a period of several years. These savings can be split proportionally according to the intended timeline in a post-processing exercise without a major impact on the results, so long as the sequence of the ECMs is correct.    

      Calculate Savings from the Baseline: The final run of the proposed energy model will produce energy, carbon and cost information that should be compared to the baseline energy model to determine anticipated savings. During this exercise, project teams should consider the following:  

      • The energy model provides energy costs for each run, but it may be beneficial to conduct advanced tariff analysis that evaluates the anticipated annual hourly energy consumption for each package. Given the energy consumption results from the model, and the implementation timeline, a composite file of hourly data can be created to accurately reflect the percentage of each ECM that has been implemented each year. This will result in an energy consumption profile that reflects the expected annual peak and associated demand charges. More accurate utility costs can be calculated using this information. At a minimum, a utility cost escalator should be applied to the initial calculated energy cost savings to capture the impact of changing rates over time.  
      • The anticipated CO2 emissions reductions associated with each ECM can be calculated by overlaying today’s carbon coefficients onto the energy savings results. For a greater level of accuracy, the carbon coefficients from LL97 can be overlaid on the annual energy consumption for the years where this data is available (2024-2029). Beyond 2029, project teams should consider different electrical grid decarbonization projections and overlay evolving carbon coefficients on the yearly energy consumption. For example, New York’s Climate Leadership and Community Protection Act (CLCPA) targets 70% renewable energy by 2030. Assuming the grid meets the goals and schedule of the CLPCA, the carbon coefficient for electricity for the year 2030 will be much lower than it is today.  

      Outputs

      The final energy modeling results should include energy savings, energy cost savings, and CO2 reduction for each ECM package studied.

      Lessons Learned & Key Considerations  

      Total carbon emissions depend on the building and the grid: While building owners have control over how efficient their building is, they cannot control the long-term decarbonization of the electrical grid. Building owners can and should evaluate how they can optimize the energy performance of their building through the implementation of ECMs, but the total associated carbon emissions produced by the building will depend on both the magnitude of the energy consumed and how carbon-intensive the source of energy is. For this reason, it is beneficial to understand how different grid scenarios and emissions factors impact the ECM results. A cleaner grid in 2030 may be the difference between meeting or exceeding the LL97 emissions limit for that year.

      Strategic Decarb 101

      Resource Efficient Decarbonization Guide

      Bookmark

      This guide presents a three-step process for real estate owners, in coordination with engineers and designers, to develop a technically and economically feasible decarbonization plan for their building.  This holistic approach is informed by lessons learned from low-carbon demonstration projects funded through the Empire Building Challenge to help building owners develop and adopt successful plans for retrofitting their building. 

      Source: NYSERDA

      Strategic Decarb 101

      A Rational Approach to Large Building Decarbonization

      Bookmark

      Assessment Tools

      Technical Barriers to Decarbonization

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      Insights from Empire Building Challenge

      Large commercial and residential buildings must overcome various hurdles before implementing deep retrofits or capital projects that help achieve building decarbonization. This section addresses technical barriers and questions often faced by building owners and retrofit project developers.

      Decentralized Systems and Tenant Equipment

      • Access to Occupied Spaces.
      • Lease Concerns.
      • Regulatory Limitations of Rent Stabilized Apartments.
        • The building owner is required to provide free heat and hot water.
        • No mechanism to recover investment in new systems is necessary to achieve decarbonization.
        • Buildings are capital constrained.
      • Split Incentives (e.g. tenants pay for energy).

      Facade and Windows

      • Work must be completed at the end of facade/window useful life; very long useful life.
      • Building codes.
      • Glazing reduction at odds with aesthetic/marketability concerns.
      • Difficult installing with occupied spaces.
      • Reduce Local Law 11 recurring cost via overcladding
        • Aesthetic concerns
        • At odds with historic preservation
        • Capital intensive
        • Lot line limitations
      • Technology Limitations
        • Need higher R-value/inch for thinner wall assembly:
          • Vacuum insulated panels
          • Aerogel panels/batts
          • Zero-GWP blowing agents for closed cell spray foam (nitrogen blowing agent needs to be more widely adopted)

      Ventilation

      • Energy Recovery Ventilation (ERV)
        • Space constraints
        • System tie-in point accessibility/feasibility
      • Rooftop Supply Air (Reznor) Unit Alternatives
        • Heat pump alternatives to eliminate resistance heat
        • Combine with ERV
      • HVAC Load Reduction (HLR) Technology
        • Vent or capture exhaust gases
        • Space constraints
        • System tie-in point accessibility/feasibility
      • Central vs. Decentralized Ventilation Systems
      • Direct Outside Air System (DOAS)
        • Modular perimeter ducted air heat pumps:
          • Competition for leasable space
          • Space constraints
      • Ventilation Points-of-Entry
        • Aesthetic concerns
        • Lot line facades/building setbacks
        • Competition with leasable space
        • Space constraints

      Heat Pump Limitations

      • Variable Refrigerant Flow (VRF)
        • Fire and life safety concerns about volume of refrigerant gas located within occupied spaces.
      • Regulatory risk from new refrigerant policies
      • PTAC and VTAC
      • Ducted Supply/Exhaust Air Source Heat Pumps
      • Domestic Hot Water
        • Central DHW Systems:
          • Limited domestic production.
          • Performance not confirmed by independent third parties.
          • More demonstration projects needed.
        • Decentralized DHW Systems
      • More open-source interconnection between devices/interoperability is needed to achieve energy distribution flexibility and capacity expansion:
        • Air source that has a manifold connection to interconnect with water source or refrigerant gas distribution.
        • Interconnectivity/simplified heat exchange between refrigerants/water/air, etc.
        • Other options and add-ons.

      Steam Alternatives and Barriers

      Below are high temperature renewable resource alternatives to district steam. These alternatives are limited and face barriers to implementation due to cost, scalability, and other factors. 

      • Deep Bore Geothermal
      • Renewable Hydrogen
      • Carbon Capture and Sequestration
      • Biomethane
      • Electric Boilers
      • High-temperature thermal storage
      • Hight-temperature industrial heat pumps
      • Waste Heat Capture and Reuse
      • Fission

      Barriers to Electrification and Utility Capacity Limitations

      Building Electric Capacity Upgrades

      • Electric riser capacity
      • Switchgear expansion
      • New service/vault expansion/point-of-entry space constraints
      • Capacity competition with other electrification needs:
        • Space heat and cooling
        • DHW
        • Cooking
        • Pumps and motors

      Local Network Electric Capacity Upgrades

      • Excess Distribution Facility Charges (EDF)
      • Contributions in Aid of Construction (CIAC)

      Gas Utility Earnings Adjustment Mechanisms (EAM) focused on System Peak Demand Reductions

      • Partial Electrification concepts achieve deep decarbonization but do not necessarily achieve peak gas demand reductions (debatable)

      Total Connected Loads and Peak Demand drive need for capacity upgrades

      • Demand reduction strategies do not obviate capacity limitations unless the utility accepts the solution as a permanent demand/load reduction strategy.
        • Battery Storage:
          1. Fire danger
          2. Space constraints
          3. Electricity distribution limitations
          4. Structural loads
        • Building Automation/BMS/Demand Response:
          1. Cost
          2. Integration limitations; Blackbox software
          3. Microgrid development cost and lack of expertise
        • On-site Generation:
          1. Space constraints
          2. Gas use; Zero carbon fuels availability is non-existent
          3. Structural loads
          4. Pipe infrastructure

      Thermal Storage

      • Space constrains
      • Structural loads
      • Technology limitations:
        • Vacuum insulated storage tanks
        • Phase change material (DHW, space heating)

      Geothermal (ambient temperature), Deep Bore Geothermal (high temperature) or Shared Loop District Energy Systems provide cooling and heating with lower peak demand than standard electric equipment

      • Building pipe riser limitations; need additional riser capacity:
        • Building water loops are typically “top down” – cooling capacity is typically located at rooftop mechanical penthouses; cooling towers at roof. Some exceptions to this rule
        • Space Constraints
      • Drilling Difficulty:
        • Outdoor space constraints for geothermal wells
        • Difficult permitting
        • Mud and contaminated soil disposal
        • Overhead clearance constraints for drilling in basements/garages 
      • Shared Loop/Thermal Utility Limitations:
        • Requires entity that may operate in public ROWs and across property lines
        • Utilities are limited by regulations for gas, steam or electric delivery versus shared loop media (ambient temperature water).
          1. Only utility entities can provide very long amortization periods
          2. Utilities are best suited to work amid crowded underground municipal ROWs.
      • Deep Bore Geothermal Limitations:
        • Requires test drilling and geological assessment
        • Seismic risk
        • Drilling equipment is very large – more akin to oil and gas development equipment
        • Subsurface land rights and DEC restrictions

      Other Energy Efficiency/Conservation Measures with proven/attractive economics (these measures are limited by lack of capital or knowledge)

      • Lighting with lighting controls
      • High-efficiency electrically commutated motors (ECM)
      • Variable Frequency Drives (VFD) on pumps and motors
      • Retro-commissioning tasks and maintenance

      Behavioral Modification

      • Staggered work scheduling
      • Telework

      Submetering and billing, potentially creates split incentive between landlord and tenant

        Crossover Device or “Magic Box” Technology

        These include multi-purpose technology for heating, cooling, heat exchange and ventilation, filtration, and/or domestic hot water.

        • Domestic production and supply chain is limited.
        • Small players operating in this space.
        • Technology is not tested over long operational periods (providers include: Daikin, Nilan, Zehnder, Drexel und Weiss, Minotair, Build Equinox, Clivet).

        Zero Carbon Fuel Limitations

        • Green Hydrogen
        • Renewable Natural Gas

        Low-Carbon Fuels

        • Biofuel
        • Biomethane

        Renewable Energy Procurement Limitations

        • REC Purchasing:
          • NYSERDA monopolizes REC purchasing from renewable energy projects.

        Pending Carbon Trading Programs Limitations

        • Deployment timeline is highly uncertain.
        • Price per ton of carbon is highly uncertain and will likely be volatile/low based on previous emissions trading scheme outcomes.

        Engineering Solutions

        Low Carbon Multifamily Retrofit Playbooks

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        These playbooks summarize retrofit strategies that maximize occupant comfort and energy savings through a transition from fuel to electricity- based heating, cooling and hot water systems.

        Playbooks are organized by building system— lighting & loads, envelope, ventilation, heating & cooling, and domestic hot water– detailing common existing systems, typical issues, and recommended measures.

        Source: Building Energy Exchange

        Engineering Solutions

        Empire Technology Prize

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        The Empire Technology Prize is a $10 million competitive opportunity for global solution providers focused on advancing building technologies for low-carbon heating system retrofits in tall commercial and multifamily buildings across New York State. This NYSERDA initiative, administered by The Clean Fight with technical support from Rocky Mountain Institute, includes a $3 million sponsorship from Wells Fargo. Accelerating low-carbon building retrofits is fundamental to New York State’s national-leading Climate Act agenda, including the goal to achieve an 85% reduction in greenhouse gas emissions by 2050.

        Source: via The Clean Fight