Retrofit Playbook for Large Buildings Launch Event
On June 11, 2024, NYSERDA, BE-Ex, RMI, and Urban Land Institute hosted the launch of the Retrofit Playbook for Large Buildings, showcasing replicable approaches for low-carbon retrofits from cohorts of the Empire Building Challenge. Additionally, NYSERDA announced its newest cohort of the Empire Building Challenge (EBC), featuring a number of leading affordable and low-to-medium income housing projects.
Opening Remarks
Michael Reed, Acting Head of Large Buildings, NYSERDA Joe Chavez, Deputy Director, Resilient & Efficient Buildings, NYC MOCEJ
The Role of Design Charrettes in Building Decarbonization Planning
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?
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.
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.
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.
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.
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:
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.
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.
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.
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?
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.
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.
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.
Architectural drawings will be used to build the energy model geometry and assign performance characteristics to exterior wall assemblies.
Mechanical, Electrical and Plumbing Drawings: · Mechanical Schedules · Mechanical Riser Diagrams · M-Drawings (Schedules) of Retrofit/Upgraded Equipment or a Description of Changes · Electrical Schedules · Electrical Riser Diagrams · Lighting Schedules and Detail Sheets · Plumbing Schedules · Plumbing Riser Diagrams
MEP drawings will be used to build the energy-consuming systems in the energy model. These documents will also inform opportunities for equipment replacements based on end of useful life and can be referenced when evaluating equipment locations and available space.
Utility Data: · Minimum 12 months of data for all incoming utilities including electricity, natural gas, district steam, fuel oil · Data from tenant electrical sub-meters (if available) · Data from central plant BTU meters (if available)
Building utility bills showing annual energy consumption and tariffs are required to create an initial energy model. Utility bills allow the energy modeler to calibrate the total energy consumption and the breakdown by fuel type, which is important to track as different fuel sources have different greenhouse gas emissions and associated energy costs.
BMS Operational Information: · Fan run hours · Damper and valve positions · Air and water flow rates · Air handling unit supply air set points · Space temperature set points · Air, water and space temperatures · Chiller/cooling tower/boiler entering and leaving water temperatures · Pump flows during peak and off-peak times · Fan and pump electrical consumption and demand data from VFDs
Relevant BMS parameters include: · Meter data · Equipment hours of operation · Temperature setpoints · Data trends · Fault detection · System mode (manual versus override)
Historical data from the BMS can help align modeled energy use breakdowns with actual operation. Collating and reviewing this data can provide insights into building operations. Sometimes building operation differs from the document design, standards, and even the facilities team’s own understanding as system modifications are made incrementally over the years. Live data can be used to verify system schedules, turndown, and setpoints and drive even more accurate modeling of building operations. Building management systems provide insight into how the building is performing in real-time.
Operator Interviews
Information gathered from building operators can provide deep operation insights, serve to develop trust, and identify areas of opportunity for improvement.
Existing Capital Plans
It is also important to gather data on the “business as usual” (BAU) plan for future capital and operational expenditures. Doing so allows the team to compare ECMs against already planned expenditures and to begin to understand the sequence and timing of ECMs within the context of already-planned building upgrades.
Lease Turnover Schedules
Having insight into lease turnover schedules can help define opportunities for engaging tenants in the low carbon retrofit process and identifying proper phasing of decarbonization solutions in tenant spaces.
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/Assessment
Goals
Reference/Procedure
Building envelope performance and infiltration
Understand 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, IT
Identify 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 seasons
Determine 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 controls
Verify 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 controls
Verify 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 faults
Identify 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
Investigation and discovery are an iterative process: — Information from all avenues including reviewing design drawings, walking the building, talking to the facilities team, and performing building tests will be required to create a full picture of the building’s existing condition. Consistent feedback is the key to success.
Organization should be a top priority: — The amount of information collected on the building will be significant. To ease the burden of developing an energy model for the building, information should be verified and organized so that it can be easily referenced throughout the project.
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
Visualize the data: — Data visualizations can bring insights to light and help project teams explain these insights to non-technical audiences. Making complex energy analysis accessible to all members of the project team, including those without technical backgrounds, will lead to a more engaging and actionable process for all.
BPS impact assessments can alter the deep energy retrofit approach: — Mandates and building performance standards are often successful in getting building owners to think more critically about existing building energy and carbon performance; however, the anticipated impact of a BPS can alter how the project team approaches a deep retrofit project. For example, if an Owner discovers that their building is not subject to non-compliance penalties until 2030 or 2035, they may elect to wait on larger retrofit projects than they would have if penalties were imminent in 2024. It’s important that project teams review BPS exposure with the Owner before settling on a particular decarbonization strategy or timeline.
Consider the grid: — When evaluating a building’s anticipated performance over time in the BAU base case, the project team must take grid decarbonization into account. The overall outlook for the building can change drastically with and without grid decarbonization. Both scenarios must be explored and discussed with the building owner and management team.
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
Solicit feedback early and often: — In any deep energy retrofit study, there will be several opportunities for the building to reduce energy and carbon. Some of these strategies will be reasonable to the building management and ownership teams, and others will not. To avoid going down the wrong road and analyzing a set of solutions that don’t align with the building team’s vision, the project team should present potential strategies early on and gain consensus on the decarbonization approach before analyzing measures in the building energy model.
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.
Step-by-Step Process to Advise Decarbonization Efforts
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.
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.
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.
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.
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.
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.
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:
