Spark Tool Technical Capabilities: Building Renewal Project Assessment


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Introducing Spark
Customer Benefits
How Spark Works
Match Customer Project Buildings With Spark Prototypes
Energy Efficiency Measures & Integrated Measure Packages
Validity/Validation of Results
Best Practices
Next Steps

Introducing Spark

Through its BetterBricks program, the Northwest Energy Efficiency Alliance (NEEA) and its utility partners pioneered building renewal and developed Spark, a business case tool that provides strategic, technical, and economic guidance for real estate investors, developers, and design professionals who wish to revitalize commercial office buildings. Spark’s analysis and reports are also intended to inform customer decisions regarding building renewal projects and by doing so, accelerate the adoption of deep energy retrofits in leased commercial office space across the Northwest. This document describes Spark’s technical capabilities, customer benefits, and resources NEEA used to develop the tool.

Spark is designed to assess the value creation potential from deep energy retrofit/building renewal of commercial office buildings. Spark:

Provides a building renewal/deep energy retrofit project scope as an integrated package of energy efficiency measures;
Facilitates quick comparison of different project scenarios, including sensitivity analysis of project economics;
Estimates project cost and energy and energy expense savings; and uses that information to assess the real estate value that might be created by renewing and repositioning a building.

Spark delivers a simple, user-friendly analysis, in the form of project scenarios. Users define scenarios based on answers to 58 questions about major building characteristics and potential project options, to produce a building-specific, integrated energy efficiency measure package.

Customer Benefits

Spark is easily accessible. A complete, initial pass through the user interface should take users no more than an hour (assuming utility billing and energy use information is compiled beforehand). Users can easily  explore different building renewal scenarios. The answer fields for some of Spark’s questions are pre-populated with hints; users can enter the value suggested by the hint to conduct a quick initial run, and fine tune results  as additional project team members and more detailed information is obtained. In the absence of full information, Spark users are encouraged to answer questions with their best guess. It is easy to fine-tune results.

Spark will save time and money. Users can quickly evaluate the potential for deep retrofit savings and project costs before investing time and fees on building audits, energy studies, and energy models. After Spark has demonstrated there is sufficient potential, user should form a project team to deliver the additional assessment needed to support a final investment decision.

Spark highlights market opportunities. By enhancing customers’ understanding of how energy efficiency fits into an overall real estate investment strategy, Spark places energy efficiency within a business context.  Unique opportunities are highlighted and benefits comprehensively evaluated rather than as standalone project drivers.

How Spark Works

For each project, users can run an unlimited number of scenarios, and for each scenario, Spark users receive the following analysis:

Summary of existing building characteristics and energy use
Building- and project-specific integrated package of energy efficiency measures, based upon building characteristics and user choices
An alternative integrated package of measures providing enhanced energy savings
Estimate of project costs for both measure packages
Annual electricity and gas savings estimates, in both energy units and dollars

An Analysis page provides Spark users with options to conduct sensitivity analysis of project financial returns. Users can modify scenarios to explore the combination of factors that influence project returns and to determine project areas for further analysis. From the analysis page a user selects a scenario—either the Selected Measures or  Enhanced Savings—for reporting purposes (capturing any sensitivity analysis adjustments). Spark produces a scenario specific report that summarizes the following:

Project economics summary including returns, energy cost savings, implementation cost, and non-energy benefits.
Detailed efficiency measure descriptions, including measure intent, performance criteria, design and construction implications.
Detailed descriptions of relevant best practices, including measurement and verification, commissioning, operations and maintenance, and tenant procurement protocols; to support getting started with low cost-no cost energy improvements, and to help ensure that post-renewal energy performance is achieved or exceeded.

Spark’s energy analysis is built upon the capabilities of US Department of Energy’s (DOE) EnergyPlus, a sophisticated hour-by-hour energy modeling tool, including the OpenStudio Application Suite [see sidebar description]. Typical Meteorological Year (“TMY”) Weather Data for the building location is used. Spark does not develop and run a full energy model of each building; rather, a full energy model of a prototype office building is run. Spark matches the user’s building and retrofit characteristics with the characteristics of an office building prototype, developed from NEEA’s demonstration projects. By comparing the actual energy use information of a user’s building to the results of the prototype energy model, a customized order-of-magnitude energy savings estimate is developed. Measure cost indices, also derived from the demonstration projects, are used to estimate an overall project cost.

Within the Spark user interface, structured in a survey format, users answer questions about building characteristics, and the value creation opportunity from building renewal. The number of these questions varies--depending on the answers and relevant heating, ventilation, and air-conditioning (HVAC) systems—but will not exceed 58 questions. The questions are organized into categories, so that a user’s ordered responses suggest appropriate opportunities for load reduction and smaller (down-sized) plant and HVAC equipment. With this streamlined approach, Spark delivers important elements of energy modeling, without requiring consideration of the hundreds of criteria that need to be addressed to build a detailed, calibrated energy model.

Spark presents questions in nine categories:

Building age, size, location, etc.
Utility-related questions about annual electricity and fossil fuel use and expense
Building envelope questions, addressing windows, insulation, and leakage
Lighting and plug load control
Distributed HVAC systems
Where applicable, chillers and chilled water distribution
Where applicable, boilers and heating water distribution
Where applicable, VAV or Constant volume systems
Questions that further inform Spark’s business analysis and valuation components

Based on the answers to these questions, Spark assembles one or more packages of improvements that make sense for a given building. For these packages, calculated energy savings and project cost estimates are developed. These savings and costs are combined with information provided in answers to the business profile questions to calculate the internal rate of return and present values of costs, expenses and other market benefits. These financial results are reported by the Spark Building Renewal Tool, to summarize the overall value creation potential.

Capabilities for sensitivity analysis are built into Spark and are accessible via Spark’s Analysis page immediately after a scenario is processed. Projected energy savings, estimated project cost, and the amount of project incentives can each be adjusted higher or lower with the impact of these adjustments seen in real time.

Energy Analysis

Using the building characteristics and choices entered by the user, Spark selects a pre-defined prototype building or seed that most closely matches the user’s project building. This match is made primarily on the basis of HVAC system type, but also considers building size and the number of floors. The development of these seeds saves the user the time required to create a new energy simulation model. The seed energy models are used by Spark to predict the potential future energy performance of a user’s building, following implementation of a select set of energy efficiency measures. This performance is compared to actual energy use, defined by the users, to determine energy savings.  

The modeled energy performance of these seeds has been calibrated using the energy models developed for NEEA’s demonstration projects. Through the seeds, there is a direct linkage connecting your buildings with the performance of well-understood existing buildings. While a selected prototype will not completely match a project building, it is close enough to reasonably define the future energy performance of an energy efficiency measure package, and to demonstrate what investments will be needed in building improvements to reach the objective of 35 percent or greater energy expense savings.

Spark recommendations are based upon a variety of factors. Some are straightforward, such as the reduction of lighting power density to a target level, or the use of LED task lighting. Other recommendations are based upon analysis using proxies, such as the age of equipment and system components, to choose between retrofit or replacement options.  

For energy efficiency measures that have either a major impact on building occupants or the most significant implementation costs, such as chiller or window replacement; even though they make very significant contributions to energy savings, Spark analysis offers the user an opportunity to opt out of the measure. By doing so, alternative scenarios can be explored, with and without the measure, to consider the tradeoff between measure cost and savings.

Project Cost Estimating

Each energy efficiency measure (see list below) has an indexed cost (in $/square foot of building floor area) embedded in the Spark database. The indexed costs for each measure were derived from detailed cost analysis that was conducted as part of NEEA's deep retrofit demonstration projects.

Unlike energy performance, which is predicted using a prototype model, with most or all of the applicable measures included, the project cost estimate only uses costs associated with measures that represent an “add” to an existing building. Spark uses the information collected during the user surveys to determine which costs need to be included and which do not. For HVAC retrofit measures, this can even include the costs associated with some system components while excluding costs associated with other system components.

For example, if an existing packaged VAV system has a new furnace but has aging air conditioning components, the cost for packaged VAV retrofit would include the replacement air conditioning compressors but not the furnace. All indexed costs are intended to represent project costs.

Soft costs, including design, commissioning, and other project administrative costs, are accounted by means of a multiplier that is location specific and applied to the total project cost estimate. 

Energy Efficiency Measures and Integrated Measure packages

Spark uses just over 20 energy efficiency measures, in six categories, that have been derived from NEEA’s building renewal development efforts and demonstration projects. These measures have been identified as the most significant contributors to energy savings, when integrated into an ordered integrated measure package that recognizes the benefits from heating and cooling load reduction before sizing HVAC systems.

Spark’s energy efficiency measures are not prescriptive measures, but are described on a performance basis, to facilitate each project team’s determination of how best to reach targeted energy performance. This flexibility is essential for project teams to apply efficiency measure guidelines to align with project building conditions. The brief descriptions below summarize the measures built into Spark, from which integrate Measure Packages can be assembled.

Spark Efficiency Measures



Wall Insulation

Reduce the heating and cooling conductive load of the exterior walls, including thermal bridging, and increase the effective U-value of the exterior assemblies.

New Windows

Replace old, low-performance window assemblies with high-performance units offering better thermal performance.

Secondary Glazing System

Secondary glazing systems are a retrofit product that consists of a high-performance glazing unit and frame mounted on the interior side of an existing low-performance window, to significantly improve thermal, visual, and acoustic performance (and occupant comfort and health)

Reseal Envelope

Reduce air leakage through the building enclosure.

Lighting Power Reduction

Reduce lighting load by delivering lower ambient lighting and high quality task lighting at each workstation.

Perimeter Daylighting

Combine integrated perimeter daylighting with a reduction of lighting power density.

Occupancy-based Lighting Controls

Reduce and/or turn off electric lights when unnecessary due to lack of occupancy.

LED Task Lighting

Replace existing task lighting incandescent lamps with 6W or 9W LED lamps, or provide new task lighting with dedicated LED fixtures. Incorporate integrated vacancy sensing into task lighting.

Occupancy Sensor Controls

Reduce plug load energy use by de-energizing or reducing the power draw of office equipment during times that it is not in active use.

Built-up VAV Retrofit

Using the existing HVAC infrastructure, retrofit each element to its maximum performance level; this may require re-construction and/or replacement; cleaning and/or repair.

Packaged VAV Retrofit

Many small and medium-sized office buildings are served with packaged variable air volume (VAV) HVAC systems that have major components (such as air handlers, furnaces, and terminal units) with significant remaining service life. An HVAC restoration will retrofit each targeted element to its maximum performance level.

Hydronic Heat Pump Retrofit

Retrofit of hydronic heat pump systems involves change-out or upgrade of one (or a limited number) of the existing system components while keeping the existing system operational and functional. This typically involves repair or replacement of individual heat pumps to improve heating and cooling efficiencies, and increase service reliability of system components.

New Packaged VAV

When older packaged HVAC systems are deteriorating in many areas, it makes sense to completely replace these systems with new packaged VAV systems. New packaged systems can deliver optimized fan efficiencies, improved fan capacity controls, improved cooling efficiencies, and lower overall turn-down capabilities.

New Advanced VAV

Advanced VAV systems are designed, constructed, and controlled to minimize inherent simultaneous heating and cooling, by managing central cooling and distributed reheat coil loads, and minimizing fan energy use by managing duct pressures.

New Decoupled Dedicated Outside Air System

Separate the heating and cooling functions of a building’s HVAC system from the ventilation functions, using zonal HVAC systems and dedicated outside air systems (DOAS), with internal exhaust air heat recovery. Decoupled systems eliminate the simultaneous heating and cooling functionality that is part of all VAV systems.

New Heat Pumps

For buildings with an older and outdated hydronic heat pump system, the new hydronic heat pump measure can involve complete replacement of major system components including the individual water-to-air heat pumps, boiler, fluid cooler, or ventilation system components.

New Chiller Plant

Install a new high efficiency chiller (or chillers), with efficiency improvement of 20-to-30 percent, compared to the existing chillers.

Retrofit Chiller Plant

Upgrade aging plant equipment, improve part load performance of existing chillers to more closely match building load, and reduce noise and vibration associated with existing chillers. For many chillers, today, that have heat exchangers in reasonable condition, this involves retrofit of new high efficiency compressors with variable speed capacity controls.

New Condensing Boilers

Replace aging boilers; improve plant part load operation by installing modulating boilers and/or modular boiler plants that can effectively operate at low load conditions, without excessive cycling. Boilers designed for condensing performance often exhibit combustion efficiencies well above 90%, compared with existing boilers that may be operating in the 70% to 80% efficiency range.

Variable Flow Pumping Retrofit – Chiller Plant

Pump replacement offers the opportunity to improve the mechanical efficiency and capacity control of the pumps. This involves installation of variable frequency drives (VFDs) and conversion of the pumping system to variable flow capability. This measure applies primarily to chilled water pumping systems but can also be applied to condenser water systems in some plants.

Variable Flow Pumping Retrofit – Boiler Plant

Upgrade of existing constant flow heating water systems to energy-saving variable flow can involve some or all of the following: new piping, new pumps and motors, valve upgrade or replacement, VFD installation, and new controls.

Variable Flow Pumping Retrofit – Hydronic Heat Pump System

Upgrade of existing constant flow heating water systems to energy-saving variable flow can involve some or all of the following: new pumps and motors, motorized isolation valve installation at heat pumps, VFD installation, and new controls.

Direct Digital Controls (DDC)

Optimize existing controls, or Install a direct digital control system that controls all elements of the HVAC system and is tightly scheduled for building occupancy and other exterior influences. The system should not only execute control functions, but also collect and archive relevant building performance data for use in M&V activities.

Validity/ Validation of Results

While the pool of existing commercial office buildings is varied and complex, the steps that should be taken to achieve deep retrofit levels of energy savings tend to be very consistent. From a broad perspective—particularly when building systems and major pieces of equipment are approaching or exceeding the end of their useful life and need to be replaced and the objective is energy savings of 35 percent or more—there are a relatively limited set of options to consider.

Spark’s intent is to develop a conceptual assessment of building renewal potential focused on value creation and energy savings, not to provide a detailed energy model and in-depth analysis. By using prototype office buildings to estimate future energy performance associated with project buildings, similarities of operating schedules and density of energy use (other than data centers) are assumed. The prototype buildings represent the performance of typical mid-rise and high-rise offices in the region. They were developed from demonstration buildings that were subjected to detailed study as part of NEEA’s Existing Building Renewal initiative. They all exhibited the similar predictive performance characteristic that as more and more efficiency measures were added to the buildings, the energy performance of all projects converged on a similar Energy Use Intensity (EUI) somewhere between 30 to 40 kBtu/SF-year. This is a characteristic of the prototype buildings used in Spark. Ultimately, when all Spark measures are applied and building energy-related characteristics become roughly the same, projected energy performance of the different prototypes converges to a similar indexed energy result. This convergence characteristic allows the use of prototypes to be a valid approach to predict the future performance associated with a variety of different office buildings that are subjected to deep energy retrofit measure packages.

Best Practices

The ultimate performance of Spark’s measures and the success of a building renewal project rely upon a foundation of best practices including commissioning and effective operations and maintenance. Operations and maintenance (O&M) practices are essential for the persistence of energy savings and exploration of operations and maintenance opportunities should be the first step in evaluating the potential for building renewal. Office buildings that have indexed energy usage that is significantly higher than the norm (as shown by low ENERGY STAR® scores) are likely to be excellent candidates for a focused O&M improvement effort that could include both system tune-ups and retro-commissioning. Initial review will identify both no cost and low cost measures to deliver five percent or more energy savings, while improving tenant comfort and satisfaction. 

Ensuring 35 percent or greater energy savings requires more than the design and implementation of a set of energy efficiency measures. The following best practices are essential to achieve projected savings, and are addressed, more fully, on the website buildingrenewal.org. 

Operations and Maintenance 

First, creating a best practice operation and-maintenance (O&M) program increases the efficiency of facility staff, improves building operational practices, and reduces utility costs. An O&M program also helps sustain a building's profitability by reducing costly equipment failure and maintaining tenant comfort and indoor air quality. Establishing an O&M program is generally straightforward; it primarily reorganizes and reallocates existing resources to be more efficient and productive. Implementing a best practice O&M program can often reduce facility energy use by five percent, or more, without significant capital expenditure. Aspects of an O&M program that reduce energy costs often focus on HVAC systems and controls and include setpoint and schedule adjustments, valve and damper repair, coil and fan cleaning, and similar elements.

Occupant Criteria for Indoor Environmental Quality 

Establishing tenant comfort criteria, including thermal, visual, and acoustic, is central to any existing building renewal project. Comfort criteria should address thermal considerations such as temperature set points, exposure to thermal radiation, radiant temperatures, humidity, air speed, clothing expectations, and levels of physical activity. The intended quantity and quality of both electric lighting and daylight should be established for each space-type within the building renewal scope.

Procurement Methods

The intent of energy smart procurement is to substantially reduce plug load consumption and HVAC peak cooling loads through the use of energy efficient office equipment and appliances.

According to the 2003 CBEC data set, plug and process loads are responsible for 19% of the average US office building’s annual energy consumption end use breakdown. This represents a substantial area for energy savings. Plug and process loads become even more significant as the heating, cooling, and lighting consumption decreases in a high performance building, where it then will represent an even larger overall percentage of the building’s energy use. 

Plug loads include the energy consumption from office and general miscellaneous equipment, computers, printing, elevators and escalators, servers, kitchen cooking and refrigeration, laundry washing and drying, but excludes lighting power allowances, and other miscellaneous loads that are not hardwired into the building’s electrical system. For leased offices, procurement best practices offer an opportunity for landlord-tenant communication where a building owner can provide information to support a tenant’s energy smart procurement efforts. 

Pre-implementation Measurement and Verification 

Measurement and verification (M&V) activities prior to implementation of an Existing Building Renewal (EBR) project, focus on understanding and quantifying the existing energy use patterns of the building and identifying opportunities for improvements. The best way to achieve this is through the sub-metering of existing building energy end uses and analysis of whole building fuel use interval data. A significant reason for pre-retrofit M&V is to support the development of an accurate and meaningful energy model of the existing building, by documenting the following empirical data: 

Annual heating, cooling, fan, pump, lighting, and plug load energy use. 

Typical building daily fuel use profiles, with sufficient data collection intervals, so that occupied, unoccupied, and transition periods can be clearly distinguished. 

Data collected via pre-project implementation M&V is intended to: 

Support calibration of an accurate whole building energy model that will be an important part of the pre-implementation technical assessment. This is work that is typically expected to follow initial use of Spark. 

Identify existing system and equipment deficiencies and sub-optimal conditions that will inform development of an integrated package of energy efficiency measures. This is work that can define numerous elements of an O&M program. 

Validate pre-implementation energy use, at the end use level, to verify savings via comparison with similar post-implementation energy end use data.


Commissioning ensures that buildings operate as intended throughout their lifecycle, optimizing individual and coordinated building systems to achieve the highest performing building operation.

Retro-commissioning applies the commissioning process to existing buildings, to improve how building equipment and systems function together, and to enhance a building’s operations and maintenance (O&M) procedures to improve overall building performance. Depending on the age of the building, retro-commissioning can often resolve problems that occurred during design or construction, or address problems that have developed throughout the building’s life. 

Re-commissioning is another type of commissioning that occurs when a building that has already been commissioned undergoes another cycle of commissioning. The decision to re-commission may be triggered by a change in building use or ownership, the onset of operational problems, or some other need. Ideally, protocols for re-commissioning are established as part of a new building’s original commissioning process or an older building’s retro-commissioning process. 

Post-Implementation Measurement and Verification 

M&V activities following implementation of a building renewal project assume that the necessary infrastructure to collect relevant performance data is now in place. Post-implementation M&V applies the knowledge of the building systems operation to ensure that they are performing according to expected intent. How should a project make use of an extensive and robust M&V installation? What are the most important ongoing uses of data generated and stored by the M&V systems? Two basic uses are: 

Verify the expected energy savings, by comparing post-implementation energy use data to similar data collected during the pre-implementation period.
Diagnostics, to find ways to increase energy use to match or exceed original expectations.

Use of this data is really limited only by the imagination and creativity of the user. All project representatives should continually be generating and evaluating new ideas about how to use both the real-time and archived building performance data produced by the M&V systems.


Building renewal projects benefit from a comprehensive project team, which should include an owner’s representative deeply familiar with building operations, and an owner’s representative with responsibility for analyzing business opportunities and project economics. Depending upon the measures to be implemented, an architect and design engineers, contractor(s), and a cost estimator may be required. Spark provides the performance criteria for each efficiency measure and the results of a first-order analysis, but the project team will be responsible for the detailed analysis required for project design and implementation.

Energy Analysis

To select an appropriate and effective package of energy efficiency measures, a thorough understanding of a building’s energy performance is required. This assessment should provide a complete picture of operational performance and identify specific opportunities for improved energy efficiency. Spark’s Technical Addendum provides details of a comprehensive list of measures meriting investigation. However, given the idiosyncratic nature of existing buildings, on-site data collection is crucial. At a minimum, an investigation with the depth of a Level 1 ASHRAE Energy Audit, including in-person meetings, building tours, and site audits will be required to refine energy performance analysis and measure implementation cost estimates. Upon completion of a technical assessment and the development of a calibrated energy model, design teams and owners will have an operational Energy Use Index (EUI) that provides a baseline for energy reduction goals.

The recommended renewal measures include heating and cooling load reduction strategies that will result in cost savings from smaller heating and cooling system capacities than would otherwise be required. Remember to analyze load reduction opportunities before looking at HVAC system sizing.


Spark’s holistic assessment considers implementation of the full bundle of measures at one time, and takes a 10-year look at the economic returns from building renewal. Projects may be strategically phased as required, in a series of individual sub-projects over a number of years, timed to match the end of equipment and system lives, tenant rollover, and other opportunities, to optimize benefits and to minimize disruption and inconvenience. While developing a plan for phased implementation, customers should not lose track of the long-term, net opportunity to significantly downsize heating and cooling system capacities.

Value Analysis

Beginning with the proposed measure package, assess the value of energy savings and reduced O&M expense. Review local real estate market conditions and the value created from repositioning the building as an upmarket asset. Consider the cultural values of current tenants, especially as they relate to sustainability. What is the potential of the building renewal project to retain current tenants or to attract new tenants? What potential is there to increase the occupancy rate or rental revenue to reflect the market value of improved tenant conditions? What utility incentives are available to support the project investment? 


Building Renewal provides a comprehensive look at the value creation and other impacts of a deep energy retrofit. The value analysis and recommendations in this report might not be justified on energy savings alone. Further, this report and the value analysis and recommendations included within areestimates and should be used only as a guide in the decision making process. This report and all information and recommendations contained within is provided to you “as is” without any warranty or representation regarding quality, accuracy, or usefulness.

Open Studio Application Suite

OpenStudio is a cross-platform (Windows, Mac, and Linux), open-source collection of software tools to support whole building energy modeling, using EnergyPlus and advanced daylight analysis, using Radiance. OpenStudio is an open source project to facilitate community development, extension, and private sector adoption. OpenStudio includes graphical interfaces along with a Software Development Kit (SDK). 


EnergyPlus is a whole building energy simulation program that engineers, architects, and researchers use to model energy and water use in buildings. Modeling the performance of a building with EnergyPlus enables building professionals to optimize the building design to use less energy and water.

EnergyPlus runs on the Windows, Macintosh, and Linux platforms and models heating, cooling, lighting, ventilation, other energy flows, and water use, and includes many innovative simulation capabilities: time-steps less than an hour, modular systems and plant integrated with heat balance-based zone simulation, multizone air flow, thermal comfort, water use, natural ventilation, and photovoltaic systems. Free add-ons and other third-party software products are available for use with EnergyPlus.

OpenStudio in combination with EnergyPlus: The OpenStudio Application Suite includes five tools that work with EnergyPlus, Radiance, and other formats such as gbXML. The SketchUp Plug-in allows users to quickly create geometry for EnergyPlus with SketchUp functionality including drawing tools, integration with Google Earth, Building Maker, and Photo Match. SystemOutliner lets users create and edit HVAC systems. ModelEditor is a generic interface to OpenStudio objects. RunManager manages multiple simulations and workflows. ResultsViewer enables browsing, plotting, and comparing EnergyPlus output data in a graphical format.

The OpenStudio Building Component Library (BCL) database format has been used to define and develop Spark’s energy conservation measures.

The OpenStudio Parametric Analysis Tool (PAT) is used to house the baseline and building renewal “seed” models as the starting point to assess the energy savings impact of various building renewal energy efficiency measures and to view simulation results.

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