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What should we as architects know about ensuring that our buildings perform? This article will give an overview – from required benchmarking, actual operating data for green building certification, relying on analytical testing rather than intuition, showing building owners the incredibly fast return on modeling services, and extending the value of the services we provide.
1. Performance-based design and early modeling
There are market forces that are encouraging architects to deliver buildings that perform as designed. Energy Disclosure Laws which require regular reporting to the government or make energy performance data available when a property is leased or sold are becoming more widespread according to the Institute Market Transformation, an organization that promotes disclosure laws. At the same time, reports about buildings designed to be sustainable that miss their energy goals by a wide margin after owners occupy the buildings are surfacing with regularity. The variance of actual building performance from energy model predictions can be attributed to many causes: occupant behavior and plug loads are normalized in the simulation process and may vary significantly from expectations, energy modeling may over-simplify system interdependence, construction quality (air tightness) may vary from plan, operations may vary from anticipated use, and many other factors of design, simulation, construction and operations may play a role in performance outcomes. However, as our profession looks forward to a carbon neutral future, it becomes increasingly important to connect building design expectations with actual performance.
Voluntary rating systems such as the Living Building Challenge require actual performance data for certification and LEEDv4 is moving away from projected energy use and toward actual performance by requiring energy metering as an EA prerequisite, and having Building Commissioning including Post Occupancy Evaluation as an EA credit. Many jurisdictions are moving in the direction of true performance-based energy code compliance (12 consecutive months of code-compliant performance within 3 years of delivery), opting for voluntary compliance in the immediate future and mandatory compliance over the next few years. The growth of the Whole Building Commissioning Process is evidence of a market where building owners are interested in making certain that buildings are constructed and performing as designed. The industry is headed for more performance based and outcome-based compliance and the architect has a significant role to play in ensuring that the energy performance of the project is integrated into the overall building design.
Energy modeling informs the design process leading to a higher quality and more efficient building. Early design performance modeling allows the design team including the owner and operator to get data early to aid in making fundamental design decisions which affect a number of interrelated building systems through comparative analysis. This information is not meant to predict energy use but rather to see which of the design options being considered lead to a more efficient building by showing the design team which of the design approaches being considered will result in a reduced overall demand as well as peak heating and cooling load. For example, orientation, massing, window to wall ratio and permanent shading devices can all be studied in the early design analysis process. This analysis should be done prior to modeling whole building systems energy use. Architects can set and meet performance goals by employing computer models early in the design process. Modeling can help the design team to understand climatic data, test design options to make decisions based on data, discover integrated solutions, set project goals and find first cost savings. For example, reducing the window to wall ratio, reorienting glazing or using improved glazing might reduce cooling loads and save the project the cost of a chiller, immediately paying back for the envelope improvements.
2. Use scientific method instead of assumptions or intuition
Architects should not rely on their intuition or assumptions to make decisions or which may not be correct or are not to justify design decisions. This lack of real data makes the decisions vulnerable to being changed later in the design process which can be costly and inefficient because so much design development has already been predicated on these early design directions. For example, architects assume orientation has a significant impact on building loads, but in a location with pervasive cloud cover, orientation may have less impact than anticipated. It is better to use the Scientific Method, a logical way of answering a question. The steps of the Scientific Method can vary depending on the area of study or particular task but a hypothesis is made based on systematic observation, make predictions based on the hypothesis and then test the predictions, modify the hypothesis based on the results and test again until the discrepancies between theory and results are resolved. How often have we assumed that a certain orientation of a building will be better but unable to quantify how much better? Similarly when we are working on a project located in a climate with which we are unfamiliar how do we become familiar with it well enough to design a building there? If instead of using assumptions we are able to quantify the better performance of a particular orientation or window to wall ratio on a specific site we would understand the value of these decisions and be able to communicate this effectively to our clients and the rest of the design team.
Design teams that model their projects during Concept or Schematic Design using software such as Sefaira, Revit 360, AECOsim, Equest, Energy Plus, Insight, Diva (and others) to test different options for the orientation, massing, and ratio of glazing to solid wall know which of the options being considered perform better and by how much. These teams say that they are surprised by how often their initial assumptions are incorrect.
See the images below showing projected performance for a corporate headquarters in Cleveland OH. The design team made massing adjustments from Schematic Design to Design Development and then again at Construction Development in order to keep their energy performance goals within .
 
Nall and Crawley 2011, "Energy Simulation in the Building Design Process"
The location of a project is not just the physical characteristics of the site but the climatic conditions of the place. Software such as Climate Consultant developed by UCLA (available for free) allows us to analyze different aspects of particular climates by using data which is represented in clear easy to understand graphic charts. The program allows us to compare climates that we are familiar with to the climate that the project is located and to dig deep into specific aspects of a region when considering design solutions. This software is primarily for viewing climate data such as wind wheels, diurnal averages, ground temperature, etc. There are a few charts that start to help us develop design solutions such as the Sun Shading Chart which allows one to see which shading solutions will be most effective for a building with a particular orientation in a specific climate and the psychometric chart even quantifies sixteen specific strategies to see what will be most effective in a particular climate.
Psychrometric Chart from "Climate Consultant" program developed by UCLA. The actual temperature and humidity data. Sixteen strategies are in the box at the upper left with percentages of effectiveness displayed.
On most building types, the very first design decisions that architects make regarding the building enclosure have the greatest impact on the energy efficiency of the completed project. The orientation, massing, and ratio of glazing to wall are impactful design decisions which set the expression of the design’s “Big Idea” and these aspects of the design take significant effort to change as the design progresses further. The amount of insulation, glazing selection, exterior shading and exterior cladding systems even if very well detailed and specified will not make up for the opportunities lost if the first step is not taken consideration and intent.
3. Will clients want to pay for this?
Early Building Simulation can lead to first cost savings in the estimated construction costs by identifying efficiencies early in design and savings in overall design time because more cost impacting decisions are made earlier and modeling allows the design team to make decisions based on performance impact.
Amir Roth the Building Energy Modeling Technical Manager for the Department of Energy in his article The Shockingly Short Payback of Energy Modeling (May 23, 2016) cites a study by HOK that looked at the calculated payback of energy modeling costs as being recovered with in the first couple of months of building operations. According to Anica Director of Sustainable Design and Consulting at HOK, large building modeling costs run from $20,000 to $200,000 for their projects depending on the number of iterations of modeling, and size of the project. Often the modeling identifies first cost savings by initiating early conversations regarding Energy Conservation Measures (ECMs) such as identifying the benefits of using a radiant HVAC system instead of an air distributed system which may require that the cooling/heating load be kept within a narrower range, or the use of improved glazing to obviate perimeter heat or reduce the number of chillers required in the project. This approach has to be coordinated with the thermal performance of the enclosure but if the benefits of this strategy identified as a project goal then the team can move forward with the development of the design understanding the importance of incorporating and (hopefully improving with development) this aspect of the design. First Cost savings commonly attributed to energy modeling is the identification of unnecessary costs in the form of oversized and expensive HVAC systems. The identification of first cost savings relies on an integrative design process wherein the architect reduces building loads and the mechanical engineer to the load reduction in the HVAC design.
4. How do we do this?
After climate and site analysis, the team should set a Benchmark or Baseline model to understand the performance of a similar building. In the team can establish a Baseline model using one of methods against which the developing design can be compared. In the Building Green Webcast, Energy Modeling for Early Design Decisions: A Roundtable Discussion on Tools, Process, and Case Studies (July 2013) Prasad Vaidya explains that one can create a Benchmark or Baseline model to use for model calibration based on existing energy use such as in the case of a campus where this information can be made available or a Benchmark can be created using one of four available databases, EPA Energy Star Target Finder, CBECS (Commercial Buildings Energy Consumption Survey), Labs 21 Energy Benchmarking Tool, and California End-Use Survey (CEUS), and Building Performance Database (BPD) by DOE. Vaidya also explains that in his experience, early models are 70% accurate in predicting the actual performance of a building. The model’s accuracy grows to 90% at the end of Construction Documents and 95% during operation.
Benchmarking and Climate Studies will help the team to identify the Energy Conservation Measures (ECM) and set target Goals this effort can be initiated during an Eco-charette where the design team including the energy modeler, client, and users are represented. ASHRAE 90.1 is a good starting place for getting an understanding of baseline goals and is the standard for all LEED projects.
The next step according to Amarpreet Sethi, Modeler for DRL Group, in the Building Green Webcast, Full-Blown Energy Modeling is to find strategies for reducing the peak loads by using parametric modeling to study massing, orientation, window to wall ratio, shading and daylighting and the effect of these elements on each other. This process should result in a few options that then can be evaluated for comparative effectiveness. During Schematic Design, the team will want to do a preliminary Life Cycle Cost Analysis to understand the impact of the costs for each option. By the time the design has progressed to Design Development, the systems have been selected and are being developed in design. The majority of the big architectural decisions will have been made at this point and the balance of the modeling during the design process will finalize the ECMs and evaluate the updated designs to track that the design continues to meet the Energy Use goals.
Jillian Burgess a Building Enclosure Consultant with the Façade Group in Philadelphia makes the distinction between comparative modeling and predictive modeling. Comparative modeling looks at the relative impact of various design components. Predictive modeling is a very specific modeling technique that seeks to identify the exact energy use of a building by identifying the exact internal loads and external loads at a highly-detailed level. It is very in-depth and highly specific modeling technique that is rarely necessary. Most projects employ a type of comparative modeling that does not target the exact energy use, but rather quantifies how much better one design option is over another or how much the design is an improvement over code.
Parametric modeling uses a range of outcomes on a set of outputs. The input geometry or attribute ranges and the output goal metric ranges are usually scripted in a coding software (i.e. Grasshopper) to harness the power of computing to run several models based on a genetic algorithm. It is not related to of design and can be done on simple massing models or highly detailed models. It is a highly powerful tool that can help teams set energy goals and understand which variables have a bigger or smaller impact on the project’s goal metric (heat loads, cooling loads, electric use, UDI, etc.).
Burgess cautions "Many architects don’t get specific enough when asking the question in early schematics. I think the variables are clear (sunshades, orientation, glazing, etc), but the goal metrics are often not clearly stated. Architects often ask for energy use in early design, but often what they mean is loads, and probably more specifically external loads because that’s the only thing they are impacting with the design of the envelope. So, then, the first question should be what is the dominant external load, and how can I affect it or how does this design affect it? And in parallel, how do external loads stack up to internal loads and how do these relate to the building energy use? These questions will help you target design strategies with very little modeling effort."
Below is a table from the AIA Document An Architect’s Guide to Integrating Energy Modeling in the Design Process which identifies broad modeling goals at each stage of the design process.
5. Extending value of the architectural service
We wouldn’t buy a car if we didn’t believe that the Miles per Gallon performance data on the window sticker was not aligned with the actual performance of the vehicle. It is a simple concept; demystify the process, set goals and do the work to achieve these goals. The tools are widely available and becoming easier to use with graphic interfaces and the need to switch from different platforms to capture all of the information being assessed is being eliminated therefore they are becoming more useful. The industry is headed in that direction and there is an opportunity for architects to deepen their expertise, increase the value of our service and be a leader in this process.
Additional resources
International Building Performance Simulation Association
Climate Consultant and full suite of UCLA Energy Design Tools
AIA Architect’s Guide to Integrated Energy Modeling in the Design Process
Building Green webcast: Full-Blown Energy Modeling This is the last in an Energy Modeling Webcast series hosted by Kjell Anderson of LMN Architects and Paula Melton of Building Green.
Revit online tools for analyzing alternates
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