Barriers and Opportunities
Misunderstanding about energy codes
Within the family of building codes, energy codes can be seen as less important or urgent than those pertaining to human health, safety, and welfare (HSW). But energy codes protect us from the long term environmental risks of an unsustainable human existence; they are a noteworthy energy efficiency policy with proven efficacy. They also make our homes and buildings more comfortable and less expensive to heat and cool.
Design professionals sometimes find the dense material of code books unclear and difficult to parse. As a result, energy codes can be perceived as just another hindrance to getting a project approved for construction. Because of this opinion, design and code compliance have not been optimally integrated thus far. But code compliance is aligned with other energy efficiency goals, such as LEED accreditation and lower costs of operation. A building that meets code is not just a better building – it is a building that is well on its way to meeting criteria for a number of voluntary incentives.
Uncertainty of goals and purposes
All design professionals need greater clarity about the applications of building performance simulation tools in the early design stages. It is impossible to fully exploit a piece of modeling software without knowing what its exact capabilities are. It is also difficult for advocates to demonstrate the value of this software when many designers are unfamiliar with it. A series of questionnaires about how to better inform architects about energy simulation found that many were skeptical about the potential of software to provide decision-making support.42
The selection of appropriate technology and team expertise should happen on a project-by-project basis, and assistance from consultants or others with greater modeling experience should be considered if and when it is feasible. The key here is to eliminate the misconception that energy simulations are mostly beneficial for load calculations and showing code compliance, and also the idea that a large amount of information about mechanical systems is needed to perform an initial analysis.43 One solution for these issues is the publication of case studies that show best practices in early energy modeling.44
There is a limited amount of educational information available for design professionals without a background in building science. In a National Council of Architectural Registration Boards (NCARB) 2012 report on continuing education, 34% of licensed architects reported that they wanted to expand their knowledge of the effects of the thermal envelope on the design of building systems. Almost 36% of surveyed architects wanted more information about energy codes that could impact construction.45
However, the emerging consensus on the importance of energy-related early design decisions is encouraging the production of more educational materials suitable for architects and similar professionals.
Engaging more members of design teams in the energy modeling process means that a lack of efficient communication is a huge barrier to success. When workflow is compartmentalized and designers are only concerned with the completion of their own specialized tasks, the project suffers. Many architects still believe that only engineers and consultants should work on energy modeling, not those without building science expertise. This is a view shared by some non-architects, who feel that a superficial understanding of energy modeling results in users who do not have enough experience. On the other hand, non-experts are often among the first team members to work on a project, and can also offer valuable input on how energy considerations might affect non-energy considerations. More user-friendly software, such as the web-based program Sefaira, can help to remove technical barriers between architects, engineers, and consultants. Firms who have implemented this software report that it has helped them make more early design decisions based on data rather than intuition.46
The majority of large architecture firms are now using BIM software for some parts of their design process. In 2012, firms reporting BIM usage were most likely to use the software for design visualization (91%), coordinated construction documents (74%), and sharing models with consultants (55%). But only 24% reported using BIM for any sort of energy or performance analysis.47 On a more positive note, almost 60% of AEC degree programs in the United States now include BIM as part of their standard curricula.48 This means that a large portion of new professionals entering the workforce will already have the foundational skills necessary for energy-related demands.
An energy efficient building requires project delivery models that use a collaborative approach, such as Design-Build (DB) or IPD. As of 2012, these two methods each accounted for 2% of project value.49 Most firms still use the traditional design-bid-build arrangement, which results in the compartmentalization of design teams. However, there has been a slow but steady upward trend of design professionals using collaborative business models. As of 2011, 22% of architectural firms offered design/build services, up from 21% in 2008 and 20% in 2005.50
Interoperability is “the possibility for information to flow from one computer application to the next throughout the lifecycle of a project”51. Improved interoperability between software applications has been identified as a priority not just for energy modeling, but for the entire AEC community.52
According to some estimates, the time required to recreate the geometry and information from a BIM file for the purposes of energy analysis can take up to half of the overall time allocated for energy modeling.53 The silver lining here is that once interoperability improves, the time commitment for performing rudimentary energy analyses will be cut dramatically.
There are two kinds of fragmentation that threaten the widespread use of energy modeling. One of them is among design professionals. The other is among software platforms. A lack of interoperability among building performance analysis software means that there is a tenuous connection between energy modeling and code compliance. Tools that are suitable for making critical early design decisions are too slow to be useful in later phases; tools capable of validating code compliance have learning curves that are too steep for many design professionals. Too often, models from one phase cannot be easily packaged up from one program and imported into another.
One of the biggest barriers to widely practiced early energy modeling is transferring CAD and BIM information to BEMs. Too many variables affect the amount and quality of information that can be carried over. These include the caliber of the design model, the pre-transfer preparation, the ability of the software to recognize imported components and assign them the correct attributes, and the expertise of whoever is working on the project. If model inputs are garbled in translation, it takes a certain amount of experience to recognize this and correct it instead of misinterpreting it. Clearly, we need a better bridge between these programs, both to widen the population that modeling software is accessible to and to streamline workflow for all users.54 In recent years, more architectural software with capability to automatically generate multi-zone thermal models has become available. Earlier examples of this type of tools include Autodesk Ecotect Analysis (which is now being integrated into Revit®) and Diva for Rhino3D.5556 Difficulties in translation discourage design professionals from using existing CAD and BIM models. The elimination of this manual data duplication could result in a huge increase in productivity. Up to 50% of the time spent on a simulation is devoted to gathering and validating building performance data.57 This is obviously a hindrance to workflow during all stages of the process, but it is especially detrimental during the early conceptual and schematic phases, where being able to quickly receive results for use in the next iterative model is crucial. Modeling errors in early design could mean decisions are made on the basis of misinformation. Design professionals at all stages of their careers are realizing the importance of integration. A 2011 survey of architectural students at the University of Liverpool found that 92% thought the integration of thermal analysis software with conventional 3D modeling software would streamline the design process.58
It is readily apparent what spatial information needs to be rebuilt within the BEM interface. As it stands, users need to visually check for accuracy and make manual corrections when moving from standard design software to energy modeling software. This means opportunities for human error, compounded by the lack of communication. The onus is on the energy modeler to find the best software and the best way of transferring information. As better integration of energy analysis tools is developed, designers and modelers will be able to focus on problem solving instead of diligent data extraction and software workarounds.
The fundamental reason behind the fragmentation of software is that the aims of the two kinds of models are different. BIM software contains building geometry and spatial relationships but also can hold information about building location and the characteristics of building components. Even though they are working towards the unified goal of a functional, comfortable, efficient building, architects, energy modelers, and engineers have different representational paradigms. An architectural model that is constructed for the sake of visualizing a purely aesthetic aspect might not be usable for energy simulations. Energy modeling means shifting away from “faithful physical representation” to visualizing performance properties.59 For example, the architectural idea of a room is not the same as a thermal zone. To calculate heating and cooling loads in energy models, we have to think of a room as an enclosed volume of relatively homogeneous air.
Walls and ceilings, which in architectural models will have some given thickness, become simple surfaces that are given properties relating to rates of heat transfer. Without careful attention paid to the correct boundaries between zones, an energy model based on an architectural model can generate erroneous analysis numbers.60 Even when the transfer from BIM to BEM goes smoothly, design changes in the BIM file require a corresponding change in the energy model that often has to be performed manually. Common file formats such as gbXML and IFC have the potential to reduce these and other issues, but their uptake is limited in part by the threat they pose to the market share and profitability of privately developed software.
Building industry stakeholders have a professional responsibility to comply with the energy code, so it would be irresponsible not to collaborate to produce the optimal building. Working together more closely will encourage design professionals to trust the results of others and build upon what has already been done instead of starting from scratch. As of 2014, only 48% of consultants and designers reported that they would feel comfortable using data that had been generated by other professionals due to concerns regarding liability and data quality. Only 7% reported that they started their own work with inputs or models assembled by a colleague.61
One of the keys to improving workflow is the uptake of a common file format for communication between specialized programs. For example, a concept model used for daylighting should not have to be rebuilt from scratch so that another team can test strategies for airflow. By establishing standards, common file formats can improve project delivery times and overall productivity.62
The Open Green Building Extensive Markup Language (gbXML) Schema is a non-proprietary file type that can transfer information back and forth between BIM models and BEM. It has become the industry standard, used by Autodesk and many others. This file type helps prevent energy modelers from having to recreate a 3D model from a 2D drawing file of a building plan. This minimizes human errors that occur in translation. Examples of software that are compatible with the .gbXML file format include Autodesk Green Building Studio, Bentley Hevacomp, DesignBuilder, OpenStudio, and Sefaira.
The Industry Foundation Classes (IFC) file type is available free to all software vendors. Along with three dimensional geometry, .ifc files can hold information about project elements, such as materials, functions, and even properties like color and fire rating. However, it is only widely used during the earlier phases of design. Examples of software that are compatible with the .ifc file format include Autodesk Ecotect, Simergy, and AECOsim Building Designer.63
The building industry involves “a number of uncoordinated private and public actors” who have varying degrees of building science expertise.64 The results of a model are only as good as its inputs, which in turn depend on the knowledge of the person or persons creating the inputs. In other words, the maxim of “garbage in, garbage out” holds true here. Architects are the group of design professionals poised to effect the greatest change on building performance, but are also the group with the least amount of applicable training.
One speaker at a building energy modeling summit noted that new graduates at his firm excelled at understanding software interfaces but struggled with the underlying logic of the variables that they were modeling.65 3D visualizations make it possible to perform energy analysis without understanding all of the underlying mathematical and thermodynamic calculations, but architects still need to find a middle ground of technical proficiency in building science and performance.66 Otherwise, they will be unable to catch errors and troubleshoot if problems arise. They will also lack the ability to fully interpret simulation feedback and apply it to future design iterations.67
Not all clients are willing or able to pay for a team of consultants to conduct performance simulations. In BCAP’s survey, many respondents revealed that one of the barriers to using the performance path was their clients, who either did not have the expertise to understand the value of changing compliance paths or were unwilling to pay for it.
Many smaller architecture and engineering firms cannot afford the up-front cost of having energy modeling specialists in-house. In our survey, almost 89% of respondents who used energy modeling reported that they had in-house staff meeting those needs. Another financial barrier is the proprietary nature of many pieces of modeling software. Because of economic limitations, a number of important design decisions at some firms are still being made based on prior experiences or rules of thumb.68
An important clarification to make is that energy modeling is not necessarily more time consuming overall; it simply shifts some of the decision-making to the front end of the project. Technological advances have and will continue to bring down cost marginal costs, especially as the growing number of design professionals with building performance expertise allow smaller firms to conduct energy modeling tasks in-house. Due to the popularity of sustainable building, more and more design teams are bringing energy modeling specialists on board and using consultants. This is driving down the price of these services as multiple entities compete for design work.69
A noteworthy best practice that can offset the upfront investment is utility design assistance program management. Xcel Energy, an electric power and natural gas supplier for eight states, has successfully leveraged modeling software innovations for its Energy Design Assistance (EDA) program since 2006. This service provides energy design consulting and predictive energy modeling for new commercial construction. Since retooling their process in recent years, Xcel Energy has used a web-based tool for project management. Their engineers and consultants use a combination of DOE’s EnergyPlus simulation engine and the OpenStudio visual interface.70
Ultimately, demonstrating the value of high-performance buildings as an investment in energy efficiency will reduce reluctance among both clients and designers. In some markets, commercial tenants are already willing to pay a premium to know that they are occupying a green space and showing their commitment to sustainability, whether the building has been certified by LEED, ENERGY STAR, or another third party program.71 Although design performance modeling may increase initial costs of construction, it will reduce life cycle costs of building operation, creating competitive advantage in the marketplace.
The question of existing buildings
In places like the United States and Western Europe, where the replacement rate of new construction typically hovers in the single digits, retrofitting older buildings to meet higher efficiency standards will be part of any comprehensive approach to building energy emission reductions.72 A building’s initial construction is the most cost-effective time to ensure that it uses as little energy as possible. But even in the best-case scenario where all new construction is built to comply with the most recent model code, the United States would still fall short of many national goals for energy efficiency and building emission reductions. In BCAP’s survey of design professionals, 88.6% of respondents said that their work at least sometimes involved renovations or remodeling. In most developed nations, at least half of the building stock projected to be in use in 2050 has already been built today.73 In countries within the continental northern hemisphere, this number can be as high as 90%.74 Of the building stock built since 1949 in the United States, a significant portion has never undergone any renovation (see Figure 12).
Due to several factors including lower energy prices and a lack of awareness about building science, older buildings were frequently designed with minimal consideration for the energy code if any. They tend to use far more energy and resources than comparable modern buildings.75 Retrofitting existing envelopes and mechanical systems therefore represents an enormous opportunity to reduce emissions and save money. Although most people think of new construction when they think of energy modeling, the technology is also very useful for energy-code-related upgrades on existing spaces, where it can again be used to capture potential savings by looking at interactions between building systems. The 5.6 million existing commercial buildings in this country collectively contain around 87 billion square feet of interior space. Five billion square feet of existing buildings are renovated every year.76
Assessing existing buildings on a massive scale is one of the primary challenges that stakeholders and design professionals face. Which buildings have the greatest potential for energy savings or ROI? And within the selected buildings, which components should be switched out for those of higher efficiency? This is where the advancement of energy modeling software is very useful. A relatively new framework for existing building, called rapid energy modeling, condenses the building evaluation process into three essential elements: capture, model, and analyze. Building professionals can use existing Google Earth imagery or digital photographs as inputs to generate a simplified 3D wireframe using BIM software (such as Revit Architecture or Revit MEP, although some open source BIM for this purpose may also be available). The quantity of inputs is minimized while the quality of outputs is maximized. Rapid energy modeling it also eliminates the need for specialized energy personnel and greatly reduces the time and associated costs. It is cheaper and faster than whole building energy analyses or energy audits, yet more useful than utility bills, energy benchmarking, or carbon calculators.77
Researchers at Lawrence Berkeley National Laboratory (LBNL) and their partners have started developing a way to make rapid energy modeling even faster. The portable Rapid Building Energy Modeler (RAPMOD) is a 3D mapping system that translates information from 3D scanners and digital cameras into an energy model. A person carries this technology in a specialized backpack and captures the necessary data over the course of single building walk-through. RAPMOD is still in development but has been successfully tested in one building in Berkeley, California.78